ATA24 bombardier q400 electrical power

ATA 24 ELECTRICAL POWER © Jazz Aviation LP, 2011. All rights reserved. No part of these materials may be reproduced, stored in any material form (including photocopying or storing on any medium by electronic means) without the prior written permission of the copyright holder, except in accordance with the provisions of the Copyright Act. The doing of any unauthorized act in relation to a copyright work may result in a civil claim for damages and/or criminal prosecution.

ATA 24 - ELECTRICAL POWER

Table of Contents EPGDS . . . . . . . . . . . . . . . . . . . . . . . . 6 Description. . . . . . . . . . . . . . . . . . . . . 6 BATTERY SYSTEM. . . . . . . . . . . . . . . . . . 8 Description. . . . . . . . . . . . . . . . . . . . . 8 Main and Auxiliary Batteries. . . . . . . . . . . 10 Battery Containment Vessel. . . . . . . . . . . 12 Standby Battery. . . . . . . . . . . . . . . . . 14 Controls and Indications. . . . . . . . . . . . . 16 Battery Load Indication. . . . . . . . . . . . 16 Battery Temperature Indication. . . . . . . . 16 STBY BATTERY, AUX BATTERY, MAIN BATTERY Caution Lights. . . . . . . 18 STBY BATT HOT, AUX BATT HOT, MAIN BATT HOT Warning Lights: . . . . . . 18 MAIN 28 VDC GENERATION SYSTEM. . . . . . . 20 Description. . . . . . . . . . . . . . . . . . . . 20 DC Starter/Generator . . . . . . . . . . . . . . 22 DC Generator Control Units (GCU). . . . . . . 24 Electrical Power Control Unit (EPCU) . . . . . . 26 DC Control Panel . . . . . . . . . . . . . . . . 28 DC Transformer Rectifier Units (TRU). . . . . . 30 DC Contactor Box . . . . . . . . . . . . . . . . 32 Standby Contactor Box . . . . . . . . . . . . . 36 Controls and Indications. . . . . . . . . . . . . 38 Caution Lights. . . . . . . . . . . . . . . . 40 APU 28VDC GENERATION SYSTEM . . . . . . . 42 Description. . . . . . . . . . . . . . . . . . . . 42 APU DC Generator . . . . . . . . . . . . . . . 44 Controls and Indications. . . . . . . . . . . . . 46

DC EXTERNAL POWER SYSTEM . . . . . . . . . 48 Description. . . . . . . . . . . . . . . . . . . . 48 DC External Power Receptacle. . . . . . . . . 50 Controls and Indications. . . . . . . . . . . . . 50 EIS DC External Power Indications. . . . . . . 52 DC ELECTRICAL LOAD DISTRIBUTION. . . . . . 54 Description. . . . . . . . . . . . . . . . . . . . 54 28 VDC Circuit Breaker Panels. . . . . . . . . 56 28 VDC Avionics Circuit Breaker Panel . . . . . 58 AC VARIABLE FREQUENCY SYSTEM. . . . . . . 60 Description. . . . . . . . . . . . . . . . . . . . 60 AC Generators. . . . . . . . . . . . . . . . . . 64 AC Generator Adapter Plate . . . . . . . . . 66 AC Generator Control Units (GCU). . . . . . . 66 Voltage Regulation. . . . . . . . . . . . . . 66 Control Of The AC Generator Line Contactor . . . . . . . . . . . . . . . . 66 Protection. . . . . . . . . . . . . . . . . . .68 AC Control Panel . . . . . . . . . . . . . . . . 70 AC Contactor Boxes. . . . . . . . . . . . . . . 72 AC Contactor Box Contactors . . . . . . . . . . 74 AC Generator Line Contactors. . . . . . . . 74 External Power Contactors. . . . . . . . . . 74 Galley Load Shed Contactors. . . . . . . . 74 Controls And Indication . . . . . . . . . . . . . 76 AC Voltage. . . . . . . . . . . . . . . . . . 76 AC Load. . . . . . . . . . . . . . . . . . . 76 AC GEN Caution Lights . . . . . . . . . . . 76 AC BUS Caution Lights . . . . . . . . . . . 78 AC GEN HOT Caution Lights . . . . . . . . 78 External Power Receptacle. . . . . . . . . . . 80

© Jazz Aviation LP Rev. 1.0 - Jan/2011

Page 2 FOR TRAINING PURPOSES ONLY

ATA 24 - ELECTRICAL POWER External AC Power Protection Unit . . . . . . . 80 Controls And Indications. . . . . . . . . . . . . 82 ELECTRICAL LOAD DISTRIBUTION. . . . . . . . 84 Description. . . . . . . . . . . . . . . . . . . . 84 115 VAC Variable Frequency Circuit Breaker Panel. . . . . . . . . . . . . 84 Operation . . . . . . . . . . . . . . . . . . . . 84




List of Figures EPGDS Figure 1 – EPGDS Block Diagram. . . . . . . . . 7 BATTERY SYSTEM Figure 2 – Battery System . . . . . . . . . . . . 9 Figure 3 – Main and Aux Batteries. . . . . . . . 11 Figure 4 – Battery Containment Vessel. . . . . 13 Figure 5 – Standby Battery . . . . . . . . . . . 15 Figure 6 – Controls and Indications . . . . . . . 17 Figure 7 – Caution & Warning Lights - Batteries. 19 MAIN 28 VDC GENERATION SYSTEM Figure 8 – Main DC Generation System. . . . . 21 Figure 9 – DC Starter Generator. . . . . . . . . 23 Figure 10 – DC Generator Control Unit (GCU) . 25 Figure 11 – Electrical Power Control Unit (EPCU). . . . . . . . . . . . . . . 27 Figure 12 – DC Control Panel . . . . . . . . . . 29 Figure 13 – Transformer Rectifier Unit (TRU) . . 31 Figure 14 – DC Contactor Box. . . . . . . . . . 33 Figure 15 – DC Contactors . . . . . . . . . . . 35 Figure 16 – STBY Contactor Box. . . . . . . . 37 Figure 17 – Controls and Indications . . . . . . 39 Figure 18 – Caution Lights. . . . . . . . . . . . 41 APU 28VDC GENERATION SYSTEM Figure 19 – APU Operation . . . . . . . . . . . 43 Figure 20 – APU Starter/Generator. . . . . . . 45 Figure 21 – Controls and Indications . . . . . . 47

Figure 23 – DC EXT. Power Control & Receptacle . . . . . . . . . . . . . . 51 Figure 24 – EIS Indication - DC External Power. 53 DC ELECTRICAL LOAD DISTRIBUTION Figure 25 – DC Electrical Load Distribution . . . 55 Figure 26 – Left & Right DC Circuit Breaker Panels. . . . . . . . . . . . . . . . . .57 Figure 27 – 28 VDC Avionics C/B Panel. . . . . 59 AC VARIABLE FREQUENCY SYSTEM Figure 28 – AC Variable Frequency System . . 61 Figure 29 – AC Generation - Normal Operation. 63 Figure 30 – AC Generator . . . . . . . . . . . . 65 Figure 31 – AC GCU Location. . . . . . . . . . 67 Figure 32 – AC GCU. . . . . . . . . . . . . . . 69 Figure 33 – AC Control Panel . . . . . . . . . . 71 Figure 34 – AC Contactor Box (ACCB) . . . . . 73 Figure 35 – ACCB Contactors. . . . . . . . . . 75 Figure 36 – AC Control and Indications . . . . . 77 Figure 37 – Caution Lights. . . . . . . . . . . . 79 Figure 38 – AC External Power Receptacle and EPPU. . . . . . . . . . . . . . 81 Figure 39 – AC External Power - Controls and Indications . . . . . . . . . . . . . . . . . . . . 83 ELECTRICAL LOAD DISTRIBUTION Figure 40 – AC Distribution . . . . . . . . . . . 85

DC EXTERNAL POWER SYSTEM Figure 22 – DC External - Schematic. . . . . . 49 © Jazz Aviation LP Rev. 1.0 - Jan/2011


ATA 24 - ELECTRICAL POWER THIS PAGE INTENTIONALLY LEFT BLANK




EPGDS The Electrical Power Generation and Distribution System (EPGDS) supplies electrical energy to all electrical equipment through an AC Variable Frequency System and Main 28 Vdc Generation System. The EPGDS does energy conversion, distribution, storage, control, protection, monitoring, and indication.

Description The EPGDS has these sub-systems: ●●Alternating current variable frequency ●●Main 28 VDC generation ●●Battery ●●Auxiliary Power Unit (APU) 28 Vdc ●●External AC ground power ●●External DC ground power ●●AC electrical load distribution ●●DC electrical load distribution.

The AC variable frequency generators make 115 VAC three phase electrical power for AC systems that are not frequency sensitive, such as deicing heaters, fuel auxiliary pumps, the Standby Power Unit (SPU) hydraulic pump and the galleys. They also energize the Transformer Rectifier Units (TRU), which are part of the Main 28 Vdc Generation System to supply 28 Vdc. The Main 28 Vdc Generation System is energized by theses sources: ●●Two engine driven starter/generators ●●Two Transformer Rectifier Units (TRU) ●●Three NiCad batteries ●●Auxiliary Power Unit (APU).

The EPGDS has connections AC for and DC external power while on the ground. Note: The AC external power source does not supply electrical power for engine starting. The power is distributed by an electrical bus system. It reconfigures when an electrical power source or bus malfunction, by the automatic closing and opening of bus tie contactors. © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 1 – EPGDS Block Diagram FOR TRAINING PURPOSES ONLY

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BATTERY SYSTEM The battery system supplies aircraft engine start power, emergency 28 Vdc electrical power to the aircraft DC essential buses and to the No. 3 Standby Hydraulic Pump.

Description The battery power system of the aircraft has three batteries and switching devices to supply electrical power to the essential buses during emergency flight conditions. The main, auxiliary, and standby batteries are connected to the main feeder buses to receive a charging current. The main and the auxiliary batteries also connected to the main feeder buses to supply electrical power to start the engines. During an engine start condition, the standby battery is isolated from the main feeder bus, but stays connected to the essential buses to maintain a minimum voltage level on the essential bus. The standby battery has a related battery power bus in the right DC circuit breaker panel that is energized at all times. The auxiliary and main batteries have a related battery power bus in the left DC circuit breaker panel that is energized when the AUX BATT or MAIN BATT toggle switch is set to on.

The Battery system has these components: ●●Battery and Box, Main ●●Vent and Drains, Main Battery ●●Battery and Box, Auxiliary ●●Vent and Drains; Auxiliary Battery ●●Battery and Box, Standby ●●Vent and Drains, Standby Battery. The contactors to connect the main and auxiliary batteries are located in the DC Contactor Box (DCCB) and the contactors that control the standby battery operation are located in the Standby Battery Contactor Box (SBCB) The Multi-Function Display (MFD) electrical system page and the caution and warning lights system show battery system indications. The Electrical Power Control Unit (EPCU) supplies indication data through the two Input/Output Processors (IOP1, IOP2) located in the Integrated Flight Cabinets (IFC) to the Electronic Instruments System (EIS).

The Engine and System Integrated Display (ESID) system shows main 28 Vdc generation system electrical indications





Figure 2 – Battery System FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER Main and Auxiliary Batteries The 40 A hour batteries have a rated discharge of 40 A for one hour. The discharge rate is not linear. The capacity is usually less than the rated value when the discharge current is more than the nominal value. The left lower nose compartment door must be opened to access the main and auxiliary batteries. The main battery is located forward of the auxiliary battery. The batteries are secured to the airframe in the nose compartment with tabs that are part of the battery case cover. The case is a steel box with a removable cover to give access for inspection. It also has a vent port that attaches to a tube that routes the gas overboard through a containment vessel. The main and auxiliary batteries are 40 A hour batteries with an assembly of individual cells contained in a steel case. Each cell is connected in series to make 24 Vdc at the terminals. Solid copper bus bars are used to connect the cells. They weigh 76.51b (34.7 kg) and are 10.25 in. (260.4 mm) wide, 10.5 in. (266.7 mm) long and 9.7 in. (246.4 mm) high. The main and auxiliary batteries are self contained power sources that operate in the charge and discharge modes. The main 28 Vdc generation system supplies electrical power to the battery during the charge mode. The amount of charge current is determined by the state of charge and the internal resistance of the battery.

After a long discharge period, the initial charge current can peak at 200 A. The current rapidly decreases as the battery starts to charge. During the discharge mode, the battery supplies electrical power. The battery output voltage decreases as the current load increases. Note: The voltage at the battery terminals cannot be used as an indication of the battery state of charge. The battery has nickel and cadmium (NiCad) plates with potassium hydroxide electrolyte. The NiCad battery has relatively constant voltage for most of the discharge condition. A main power positive and negative electrical connection to the battery terminals is made with a power plug connector attached to the case. The batteries have two independent internal sensors that sense battery temperature. A Resistive Temperature Device (RTD) thermal sensor is used to measure the battery temperature for an EIS indication and a bimetallic temperature switch is used to sense a temperature exceedance for a warning indication. The internal sensor wires are routed through a circular connector attached to the battery case. The left lower nose compartment door must be opened to access the main and auxiliary batteries. The auxiliary battery is located aft of the main battery. It is secured to the airframe in the nose compartment with tabs that are part of the battery case cover.





Figure 3 – Main and Aux Batteries FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER Battery Containment Vessel The left lower nose compartment door must be opened to access the containment system. It is secured to the battery shelf with three mounting screws. The overflow containment system protects the aircraft structure and other parts from the corrosive battery gases and fluid. Each battery has a vent port that attaches to a tube to route its gases through a containment vessel overboard. The electrolyte in the battery is potassium hydroxide and water. The containment system has a bottle with a boric acid and water wetted sponge to neutralize the battery electrolyte.





Figure 4 – Battery Containment Vessel FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER Standby Battery The left upper nose compartment door must be opened to access the standby battery. The battery is secured to the airframe in the nose compartment with tabs that are part of the battery case cover. The case is a steel box with a removable cover to give access for inspection. It also has a vent port that attaches to a tube that routes the gases overboard through a containment vessel. The battery is a 17 or 40 A hour battery with an assembly of individual cells contained in a steel case. Each cell is connected in series to make 24 Vdc at the terminals. Solid copper bus bars are used to connect the cells. The 17 ampere hour standby battery weighs 38.5 Ib (17.46 kg). It is 7.7 in. (195.6 mm) wide, 8.5 in. (215.9 mm) long and 9.75 in. (247.7 mm) high. The Standby Battery is a self contained power source that operates in the charge and discharge modes. The main 28 Vdc generation system supplies electrical power to the battery during the charge mode. The amount of charge current is determined by the state of charge and the internal resistance of the battery. After a long discharge period, the initial charge current can peak at 200 A. The current rapidly decreases as the battery starts to charge.

rated value when the discharge current is more than the nominal value. Note: The voltage at the battery terminals cannot be used as an indication of the battery state of charge. The battery has nickel and cadmium (NiCad) plates with potassium hydroxide electrolyte. The NiCad battery has relatively constant voltage for most of the discharge condition. A main power positive and negative electrical connection to the battery terminals is made with a power plug connector attached to the case. The battery has two independent internal sensors that sense battery temperature. A Resistive Temperature Device (RTD) thermal sensor is used to measure the battery temperature for an EIS indication and a bimetallic temperature switch is used to sense a temperature exceedance for a warning indication. The internal sensor wires are routed through a circular connector attached to the battery case.

During the discharge mode, the battery supplies electrical power. The battery output voltage decreases as the current load increases. The 17 A hour batteries have a rated discharge of 17 A for one hour. The discharge rate is not linear. The capacity is usually less than the © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 5 – Standby Battery FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER Controls and Indications The battery toggle switch located on the DC control panel is set to BATTERY MASTER position to let the standby, auxiliary and main batteries energize the essential buses if no other DC power source is available. The battery toggle switches are set to STBY BATT, AUX BATT, and MAIN BATT positions to let the standby, auxiliary and main batteries connect to the main feeder buses to receive a charging current. Note: The BATTERY MASTER, AUX BATT, or MAIN BATT toggle switch is set to on to energize the battery power bus in the left DC circuit breaker panel. The MFD1 and MFD2 reversion switches located on the ESID Control Panel (ESCP) are used to select the electrical page on the multi-functional displays.

symbol before the numbers is used to show an overload condition of the battery. The symbol is out of view when the load is less than 100 0/0. A - symbol shows a discharge condition. Battery Temperature Indication The battery temperature indication shows the battery temperature in degrees Celsius in white numbers. The indication changes to yellow when temperature is more than 50 and less than 65°C. If the temperature is more than 65 °c, the indication will change to red. Note: The Resistive Thermal Device (RTD) supplies temperature data through the EPCU and FDPS to the EIS. Note: When the voltage or load data malfunctions, the digits are replaced by white dashes

The Multi-Function Display (MFD) electrical system page shows these battery system indications: ●●Load ●●Temperature. The battery indication has a BATT title in white letters. The indication has MAIN, AUX and STBY titles in white fonts to show the load and temperature of the main, auxiliary and standby batteries. Battery Load Indication The battery load indication shows the battery load in white numbers. The numbers show the battery output load as a percentage of the total rated output. A + © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 6 – Controls and Indications FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER The battery system malfunctions are shown with these caution lights: ●●STBY BATTERY ●●AUX BATTERY ●●MAIN BATTERY. STBY BATTERY, AUX BATTERY, MAIN BATTERY Caution Lights The STBY BATTERY, AUX BATTERY or MAIN BATTERY caution lights come on to show that the battery is not connected to its main feeder bus for charging. The caution lights receive their signals from the related contactor K25, K7 and K8. The battery system malfunctions are shown with these warning lights: ●●STBY BATT HOT ●●AUX BATT HOT ●●MAIN BATT HOT. STBY BATT HOT, AUX BATT HOT, MAIN BATT HOT Warning Lights: The STBY BATT HOT, AUX BATT HOT or MAIN BATT HOT warning lights come on to show that the battery temperature is more than 71 °c. It goes out when the temperature is less than 63°C. The inputs to these warning lights come directly from the bi-metal temperature switch located in each battery.





Figure 7 – Caution & Warning Lights - Batteries FOR TRAINING PURPOSES ONLY

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MAIN 28 VDC GENERATION SYSTEM The main 28 Vdc generation system makes and supplies 28 Vdc electrical power to the aircraft DC buses.

Description The main 28 Vdc generation system has two DC starter/ generators, one on each engine, and two Transformer Rectifier Units (TRU) to supply electrical power independently to the left and right DC bus systems. When a DC starter/generator or TRU malfunctions, the main 28 Vdc generation system automatically connects its bus to another serviceable electrical source for continuous operation. A DC external power receptacle and control circuitry allows the system to be powered from an external power source while the aircraft is on the ground.

●●DCCB Contactors ●●Standby Battery Contactor Box (8BCB) ●●DC Current Transformers (DC CT) ●●Current shunts. The Multi-Function Display (MFD) electrical system page and the caution and warning lights system show main 28 Vdc generation system indications. The direct current (DC) system operates in these modes: ●●Normal ●●Protection ●●Fault Tolerant ●●Emergency ●●Diagnostics and Monitoring.

Toggle switches located on the DC control panel in the flight compartment give manual control of the main 28 Vdc generation system. The Engine and System Integrated Display (ESID) system shows main 28 Vdc generation system electrical indications. The Main 28 Vdc Generation System has these units: ●●DC Starter/Generators (GEN) ●●DC Generator Control Units (DC GCU) ●●Electrical Power Control Units (EPCU) ●●DC control panel ●●DC Transformer Rectifier Units (TRU) ●●DC Contactor Boxes (DCCB) © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 8 – Main DC Generation System FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER DC Starter/Generator The DC starter/generator attaches to the accessory gearbox with a Quick-Attach/Detach (QAD) adapter that, once installed, stays attached to the gearbox when DC starter/generator is removed. The DC starter/generator connects to the QAD with a V band clamp to secure the assembly. The QAD has an opening that connects to an airframe duct to exhaust cooling air outside of the engine nacelle. The torque force is transmitted to the DC starter/ generator through a splined shaft that connects to the engine accessory gearbox. The DC starter/generator’s drive shaft has a shear section that breaks to protect the accessory gear box drive train from damage when too much torque is supplied. The DC starter/generator is an electromagnetic machine. When it rotates, it will change engine input mechanical torque to output DC electrical power. In the starter mode, it changes input electrical DC electrical power into a mechanical output torque. The DC starter/generator operation is controlled and monitored by the DC Generator Control Unit (GCU). The DC starter/generator is a four-pole, shunt connected, fully compensated DC generator with interpole windings, brush commutation, and an internal cooling fan. It is attached to the aircraft accessory gearbox. The DC starter/generator has a permanent magnet so that it can make output voltage without an external excitation source. The output from the DC starter/ generator is sent to the DC GCU. The DC GCU supplies © Jazz Aviation LP Rev. 1.0 - Jan/2011

the DC starter/generator with its output voltage until the DC GCU starts regulation. When regulating, the DC GCU supplies a modulated current to the DC starter/generator to maintain a 28.5 Vdc output. The DC starter/generator has stator and rotor assemblies contained in a cylindrical shaped housing. The housing is made of a high iron content material. It is part of the magnetic circuit for the starter assembly. The rotor assembly has a rotor winding that connects to the fixed input terminals on the machine housing through a brush/commutator assembly. The machine housing has 4 poles with a four brush block assembly to switch the input or output current to the correct rotor winding. The rotor is held at each end by ball bearings that are mounted in the housing. The ball bearings are pre lubricated with grease when installed and service is not necessary until overhaul. The DC starter/generator has a fan to supply a forced air flow axially through it to cool the rotor and starter windings, the commutator assembly, and the bearings. Air is drawn from outside the nacelle through NACA vents to keep the operating temperatures satisfactory. The brushes that are used in the DC starter/generator have optimum life when blast cooling is supplied by propeller thrust to lower their temperature. The DC starter/generator electrical power circuit has a 4 pole shunt that operates at 12,000 rpm. The electrical circuit of the DC starter/generator has interpole windings to help the flux path between the stator and rotor to increase generator efficiency. The DC GCU supplies a control current to the shunt field winding of the DC Page 22 FOR TRAINING PURPOSES ONLY



Figure 9 – DC Starter Generator FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER starter/generator to control its output voltage. The shunt field winding current is amplified by the rotational energy of the engine to make the rated output of 400 A at 30 Vdc. The DC starter/generator terminal voltage is monitored by the EPCU for CBIT functions. Inputs and outputs of the stator windings are given by connections on the body of the DC starter/generator. Low current connections are made with a circular connector and high power output connections are made to studs mounted on a terminal block. A bonding stud on the housing of the DC starter/generator is used to connect it to the airframe ground potential. The DC starter/generator has a temperature switch that closes a set of contacts when the temperature of the DC starter/generator is excessive. It gives continuity through two pins on the DC starter/generator connector to make the DC GEN HOT indication come on in the caution and warning lighting panel.

DC Generator Control Units (GCU) The DC GCU controls the DC starter/generator start and regulation modes. The DC GCU senses the DC starter/ generator speed and it stops the start mode when the speed of the engine is more than 50%) NH. At the end of the start mode, the DC GCU opens the bus contactor and de-energizes the DC starter-generator.

voltage to maintain a constant voltage at the Point of Regulation (POR) under different load conditions. The DC starter/generator speed and voltage will increase when the engine is operating. When the output voltage is more than ±1 Vdc of the bus voltage, the DC GCU will cause the bus contactor to connect the DC starter/generator to its main feeder bus. When the two main feeder buses are connected together through K21 by a MAIN BUS TIE toggle switch selection or EPCU reconfiguration, a signal is sent to each DC GCU to make the DC starter/generators load share. The DC GCU regulates the DC starter/generator’s output and gives these protective functions: Parameter Over voltage Differential Feeder Fault Detection Bus Fault Detection Parallel Load Sharing

Value 32.5 75 A ±25 A 800 A 10% rated current

When the DC GCU senses a voltage output from the DC starter/generator, a field control contactor in the DC GCU switches from the field build up circuits to a voltage regulator circuit. The voltage regulator is a closed loop control circuit. It adjusts the duty cycle of the exciter field © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 10 – DC Generator Control Unit (GCU) FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER The DC Generator Control Unit (GCU) contains the voltage regulation and protection circuits for the DC starter/generator. Printed circuit cards, discrete power semiconductors, and electromechanical contactors are put in an aluminum box without the need for convection cooling through the box.

are supplied through output drives that use current limiting for isolation.

The DC GCU is cooled by conduction through the chassis mounting locations and by convection of air over the surface of the box. Power dissipating components in the DC GCU are attached to chassis heat sinks to transfer heat to it. Electrical connections are made with a single connector that is attached to the end of the DC GCU enclosure.

The voltage and current data is supplied to the Electronic Instruments System (EIS) through the Integrated Flight Cabinets (IFC1, IFC2) for indication. The data supplied for indication is not used for the control functions.

Electrical Power Control Unit (EPCU) The EPCU manually or automatically controls the operation of some contactors in the main 28 Vdc generation system. It manually controls contactors by flight compartment toggle switch selections. For example, a manual external DC power selection causes the EPCU to close the external power contactor. Automatic functions are used to reduce pilot work load and to start protective functions that cannot tolerate the time delay associated with a pilot selection. For example, the EPCU automatically causes the external power contactor to open when an over voltage condition is sensed. Digital logic control is used as the primary control of the main 28 Vdc generation system. Analogue to digital circuits in the EPCU changes the analogue inputs to digital format to control the system. The output signals

The critical aircraft operating functions use circuits with usually closed contactors to let the flight compartment toggle switches control the main 28 Vdc generation system when the EPCU is de-energized.

The EPCU has daughter printed circuit card assemblies and a mother board contained in an aluminum enclosure. The daughter printed circuit card assemblies connect to a mother board that connects to interface connectors. The daughter circuit card assemblies connect to the motherboard using thermal card guides for support and thermal dissipation. The EPCU is cooled by conduction through the mounting feet of the unit to the airframe and by natural convection through cooling holes near high power dissipation devices. The high power devices are attached to heat sinks on the circuit card assemblies that contact the thermal card guides when it is installed. The box enclosure has three connectors that connect to the remaining part of the system. One connector is used for the APU interface functions. A carrying handle is provided for transporting the EPCU. The EPCU has hard mounting points as an alternative to rack mounting. The EPCU has an interface panel with two push-button





Figure 11 – Electrical Power Control Unit (EPCU) FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER switches and a digital display on its front face to access fault codes. The Electrical Power Control Unit (EPCU) records main 28 Vdc generation system fault conditions. It has an interface panel on its front face to look at the fault codes

DC Control Panel The DC control panel is attached to the overhead console using four DZUS fasteners. The fasteners and a bonding wire are directly connected to the chassis to make a ground continuity connection between the backing panel and the aircraft structure.

double throw switch. The toggle lever is connected to a mechanism located in the body of the switch that moves in the opposite direction as the toggle lever. The wires from the receptacle connector are connected to the switch terminals with lugs except the bus fault reset toggle switch that has solder wire connections. The toggle switches are attached to the backing panel with mounting nuts and lock washers.

The DC control panel gives manual control of the main 28 Vdc generation system. It has these toggle switches to control the systems: ●●Batteries ●●DC starter/generators ●●External DC power ●●Main feeder bus tie ●●Bus fault reset. The DC starter/generator, standby, auxiliary, and main battery toggle switches are positive break, two pole, double throw, toggle switches. The battery master toggle switch is a four pole, double throw switch. The main bus tie and DC external power toggle switches are positive break, single pole, double throw toggle switches and the main bus tie toggle switch has a locking mechanism that locks the selection to the set position. The bus fault reset toggle switch is a four pole, © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 12 – DC Control Panel FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER DC Transformer Rectifier Units (TRU) The TRU are located in the nose of the aircraft. They are accessed by opening the upper right nose compartment door. The TRU enclosure has a rectangular shape, with the cooling air flow driven from the front face along the length of the enclosure to the rear face, where provision is included to attach ducting for routing of the hot exhaust air. The cooling air is forced through the unit using a fan mounted in the TRU at the front face. This fan is powered from within the TRU without the need for external activation and is thermostatically controlled so as to only be operational when the unit requires cooling. The enclosure provides for mounting by incorporating four hard mounting feet that bolt to the aircraft structure.

a maximum of 10 seconds. The AC generator output voltage is reduced proportionally with the frequency to prevent damage to the TRU. No active control to connect or disconnect the TRU from the AC generator is necessary. A short circuit in the TRU or related aircraft wiring will open its 3 phase AC circuit breaker. The TRU has a thermal sensor to automatically control the cooling fan. The cooling fan draws in ambient air and exhausts it outside the aircraft through a flange on the TRU attached to an airframe duct. If the TRU overheats, the thermal sensor supplies a signal to the caution and warning lights system.

The Transformer Rectifier Unit (TRU) is a self contained, solid state power conversion device that changes 115 VAC variable frequency AC electrical power to 28 Vdc electrical power. The TRU receives three phase 115 VAC power through a circular connector on the front face of the enclosure. The output 28 Vdc power is available through positive and negative studs also located on the front face of the enclosure. The TRU supplies an indication of its status for indication in the flight compartment through the EPCU. The TRU stays energized during AC generator under frequency and under voltage condition. When the frequency and voltage are decreased because of AC generator under speed operation during propeller feathering, the TRU stays connected to the load for © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 13 – Transformer Rectifier Unit (TRU) FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER DC Contactor Box The DC Contactor Box (DCCB) is installed in the nose compartment and is secured to the airframe with six mounting bolts. It weighs 76 Ib (34.47 kg) and it is 47.5 in. (1.2 m) long, 9.2 in. (233.7 mm) high and 16 in. (406.4 mm) wide. The DCCB’ is not a Line Replaceable Unit (LRU). It does not require replacement unless it is damaged. The components in the DCCB are easily accessed when its covers are removed. The components in the DCCB give control and distribution of the DC power source from the two DC starter/generators transformer rectifier units, main and auxiliary batteries, or DC external power source. The DC Contactor Box (DCCB) assembly is used to distribute and control the main 28 Vdc electrical power. The DCCB contains monitor and protection components in a protected environment. The box has covers to allow access to the internal Line Replaceable Units (LRU). The electrical power connections between contactors in the DCCB is made with bus bars. They are attached by a mounting plate assembly that secures the bus bars in the DCCB. Standard cable is used to make the connections between the mounting plate assembly and the box connectors. The DCCB has circuit breakers to protect the feeder cables that are routed directly to the aircraft equipment or to the circuit breaker panels in the flight compartment. The DCCB cover must be removed to get access to the circuit breakers.

The DCCB contains these components: ●●Diodes ●●Current transformers ●●DC circuit breakers ●●Protective fuses ●●DC starter/generator bus tie contactors, K1 and K2 ●●Main feeder bus tie contactor, K21 ●●Secondary feeder bus tie contactor, K22 ●●Secondary/main feeder bus tie contactors, K5 and K6 ●●DC external power contactor, Kg ●●Battery bus tie contactor, K7 and K8. Diodes Diodes are electronic devices that are used to isolate the direct current power sources. Current Transformers Two current transformers, identified CT1 and CT3, located in the DCCB, are used to sense the current flow in the main feeder buses. The main feeder current transformers supply current data to the EPCU differential current sense circuits. Each current transformer assembly is a toroidal (ring-type) current transformers. The cable from each phase of the system is passed through a toroid. A multi-pin connector is used to make electrical connections between the toroids and the other components. The toroidal current transformers are contained in an aluminum case and have mounting holes that are not symmetrical to prevent improper installation.





Figure 14 – DC Contactor Box FOR TRAINING PURPOSES ONLY

Page 33

ATA 24 - ELECTRICAL POWER DC Circuit Breakers The circuit breakers are installed in the DCCB to protect the feeder cables that are routed to the circuit breaker panel in the flight compartment. Protective Fuses: Two fuses are installed in the DCCB to protect the feeder cables that go to the loads. A 100 A fuse protects the ECS recirculation fan and a 150 A fuse protects the TRU and the secondary feeder bus tie contactor, K22. DC Contactors The contactors are attached to the bus bars with mounting screws and to a connector with two mounting screws. Each contactor has 400 A single pole, single throw contact arrangement with 2 sets of 5 A auxiliary contacts. Coil windings are used to move the contact arms. The DC contactors in the DC contactor box connect the DC electrical sources to the main and secondary feeder buses.





Figure 15 – DC Contactors FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER Standby Contactor Box The Standby Contactor Box (SBCB) is installed in the nose compartment or aft fuselage compartment and is secured to the airframe with four mounting bolts. It weighs 14 Ib (6.35 kg) and it is 12.1 in. (307.3 mm) long, 5.9 in. (150 mm) high and 12.03 in. (305.56 mm) wide. The Standby Contactor Box (SBCB) energizes the No. 3 hydraulic system DC Motor Pump (DCMP) and battery buses in the flight compartment. The SBCB has monitor and protection components in a protected environment. The box has a cover to allow access to the internal Line Replaceable Units (LRU). The electrical power connections between contactors in the SBCB is made with bus bars. They are attached by a mounting plate assembly that secures the bus bars in the SBCB. Standard cable is used to make the connections between the mounting plate assembly and the box connectors. The SBCB uses three circular connectors to interface with the other aircraft system components in the main 28 Vdc generation system. The SBCB has circuit breakers to protect the feeder cables that are routed directly to the aircraft equipment or to the circuit breaker panels in the flight compartment. The SBCB cover must be removed to get access to the circuit breakers. The SBCB is not a Line Replaceable Units (LRU). It does not require replacement unless it is damaged. The components in the SBCB are easily accessed when its covers are removed. The components in the SBCB gives control and distribution of the DC power source from the standby battery.

The SBCB contains these components: ●●Diode, CR 6, CR7, CR8 ●●Circuit Breakers ●●DCMP power contactor, K23 ●●Main Bus contactor, K25 ●●Essential Bus contactor, K24. Diodes Diodes are electronic devices that are used to isolate the direct current power sources. A 100 A diode is located in the SBCB. It is connected between the standby battery and the left essential distribution bus. The diode allows power to reach the essential bus but prevents the left essential bus from being the source of power. DC Circuit Breakers The circuit breakers are installed in the DCCB to protect the feeder cables that are routed to the hydraulic DCMP and circuit breaker panel in the flight compartment. DC Contactors The contactors are attached to the bus bars with mounting screws and to a connector with two mounting screws. Each contactor has 400 A single pole, single throw contact arrangement with 2 sets of 5 A auxiliary contacts. Coil windings are used to move the contact arms. The DC contactors in the standby contactor box connect the standby battery to the hydraulic DCMP and battery buses in the flight compartment.





Figure 16 – STBY Contactor Box FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER Controls and Indications

DC Voltage Indication

When the aircraft engines are operating with no external AC and DC power connected, and the DC starter/ generator toggle switches located on the DC control panel are set to GEN 1 and GEN 2, the DC starter/ generators are connected to their related DC main feeder buses for operation.

The DC voltage indication shows the DC essential, main, and secondary bus voltage in white numbers.

The DC starter/generator toggle switches are set to the OFF position to de-energize the DC generators and reset latched functions in the DC GCU. The bus fault toggle switch is set to BUS FAULT RESET position to reset latched functions in the EPCU. The MFD1 and MFD2 reversion switches located on the ESID Control Panel (ESCP) are used to select the electrical page on the multi-functional displays. The electrical page shows these DC starter/generator indications: ●●Essential, main, and secondary bus voltages ●●DC starter/generator loads ●●TRU loads.

DC Starter/Generator and TRU Load Indication The DC starter/generator load indication shows the DC starter/generator output load. The numbers show the DC starter/generator output load as a percentage of the total rated output. A 1.00 indication is used to show 1000/0. A + symbol before the numbers shows an overload condition of the DC starter/generator or TRU. The + symbol is out of view when the load is less than 100% NOTE: When the voltage or load data malfunctions, the digits are replaced by white dashes. •

The DC voltage indication has a DC BUS L and DC BUS R title in white fonts to show the voltage of the essential, main, and secondary buses. The DC load indication has a DC GEN1 and DC GEN2 title in white fonts to show the load of the DC starter/generators and it has a TRU1 and TRU2 title in white fonts to show the load of the TRU.






Page 39

ATA 24 - ELECTRICAL POWER Caution Lights

DC BUS Caution Light

The main 28 Vdc generation system malfunctions are shown with these caution lights: ●●#1 DC GEN ●●#2 DC GEN ●●L TRU ●●R TRU ●●DC BUS ●●#1 DC GEN HOT ●●#2 DC GEN HOT ●●L TRU HOT ●●R TRU HOT.

The DC BUS caution light comes on to show that the EPCU has reconfigured the main 28 Vdc generation system because of a source or bus fault condition. If the bus fault is reset, the indication will go out. The caution light receives its input from the EPCU.

#1 DC GEN, #2 DC GEN Caution Light:

L TRU HOT, R TRU HOT Caution Light

The #1 DC GEN or #2 DC GEN caution light comes on to show that the generator is not connected to its bus because of a source fault condition, the DC starter/ generator toggle switches are set to the OFF position, or external DC power is energizing the left and right main feeder buses. The caution lights receive their inputs from the left GCU and right GCU.

The L TRU HOT or R TRU HOT caution light comes on to show that the TRU has overheated. The two caution lights receive their inputs directly from the TRU.

#1 DC GEN HOT, #2 DC GEN HOT Caution Light The #1 DC GEN HOT or #2 DC GEN HOT caution light comes on to show that the generator temperature is more than 160 of (71.1 °C) and goes out when the temperature is less than 155 of (68°C). The two caution lights receive their inputs directly from the bimetal thermal sensor in each starter/generator.

L TRU, R TRU Caution Light The L TRU or R TRU caution light comes on to show that the a secondary feeder bus is not energized by its related TRU because of a source fault condition or the AC generator toggle switches are set to the OFF position. The caution lights receive their inputs from the EPCU. © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 18 – Caution Lights FOR TRAINING PURPOSES ONLY

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APU 28VDC GENERATION SYSTEM

Description

The APU 28 Vdc generation system makes and supplies 28 Vdc electrical power to the aircraft 28 Vdc buses.

The APU 28 Vdc generation system supplies 28 Vdc electrical power from a APU DC generator to these buses: ●●Left and right main feeder buses ●●Left and right secondary feeder buses ●●Left and right main distribution buses ●●Left and right secondary distribution buses ●●Left and right essential buses.

The APU supplies 28 Vdc to the main, essential and secondary DC buses while the aircraft is on the ground. The annunciator switches located on the APU control panel in the flight compartment give manual control of the APU 28 Vdc generation system. The Engine and System Integrated Display (ESID) system shows 28 Vdc generation system electrical indications. After the APU is started, the APU DC generator is available to supply power in parallel with the batteries to assist start the aircraft engines. The APU generator is connected to the right main feeder bus and automatically cross ties to the left main feeder bus to supply 28 Vdc electrical power to the DC buses. The APU 28 Vdc electrical power system has these components: ●●Generator, APU DC ●●Unit, APU DC Generator Control ●●Transformers, DC Current ●●Shunt, Current.

if there is an overload condition the EPCU will open the APU contactor K26. The APU 28 Vdc generation system is continuously monitored by the EPCU. When a malfunction is sensed, it disconnects the APU power from the aircraft buses. The APU 28 Vdc generation system has passive and active protection. The APU 28 Vdc generation system uses circuit breakers and fuses for passive protection so that a malfunction condition will not cause damage to the aircraft wiring. The circuit breakers and fuses are protection devices that open the circuit during excessive current flow conditions. Unlike fuses, circuit breakers can be reset without having to be replaced. The APU 28 Vdc generation system uses the EPCU and GCU to automatically control the APU contactor for active protection so that a fault condition will not cause damage to the aircraft wiring. The automatic functions do not need a manual selection from the flight compartment.





Figure 19 – APU Operation FOR TRAINING PURPOSES ONLY

Page 43

ATA 24 - ELECTRICAL POWER APU DC Generator The APU DC generator is attached to the APU gearbox and has a fan to supply a forced air flow axially through it to cool the rotor and starter windings, the commutator assembly, and the bearings. Air is drawn from outside the APU bay through NACA vents to keep the operating temperatures satisfactory. The APU DC generator is an electromagnetic machine. When it rotates, it will change engine input mechanical torque to output DC electrical power. In the starter mode, it changes electrical input power into a mechanical output torque. The APU DC generator operation is controlled and monitored by the APU DC Generator Control Unit (GCU). The APU DC GCU supplies the APU DC generator with its output voltage until the APU DC GCU starts regulation. When regulating, the APU DC GCU supplies a modulated current to the APU DC generator to maintain a 28.5 Vdc output. The APU DC generator supplies information to the APU DC GCU for system protection through tapping of the interpole winding voltage. This voltage is proportional to generator current and is continuously monitored by the APU DC GCU to sense unusual current levels.





Figure 20 – APU Starter/Generator FOR TRAINING PURPOSES ONLY

Page 45

ATA 24 - ELECTRICAL POWER Controls and Indications The APU CONTROL panel has the GEN control for the APU 28 VDC generation system. The APU starter/ generator is connected to the DC buses when the conditions are as follows: ●●APU is operating ●●EXT PWR toggle switch power is not set ●●GEN switchlight is pushed. The GEN switchlight is set to the off position to reset the related APU DC GCU. The GEN ON light on the APU CONTROL panel illuminates when the generator is connected to the right main feeder bus. The APU contactor K26 has connected the APU generator to the right main feeder bus. The WARN caution light in the APU control panel illuminates when contactor K26 does not connect the generator to the right main feeder bus. The WARN caution light will also come for conditions that are not malfunctions as follows: ●●The ON/WARN switchlight is not set ●●External DC power is energizing the right main feeder bus.

The PWR FAIL caution light on the APU CONTROL panel and the APU caution light on the CAWP also illuminates, and the APU shuts down. NOTE: The FAIL caution light on the APU CONTROL panel and the APU caution light on the CAWP will not illuminate if the PWR push-button is not set, except when the fire protection control amplifier has calculated an APU shutdown. The MFD ELECTRICAL system page has a digital display of the APU load. The digital display of the APU load in a white box gives an accurate APU generator load value. An APU GEN label, in white identifies the APU generator load indicator. A LOAD unit is also shown in blue with the indication. The numbers for the digital display of the APU generator load change from .00 to +1.99 in 0.01 power unit increments. A + symbol before the numbers shows an overload condition. The numbers relate to the APU generator load as a percentage of the maximum rate. If there is an open or short circuit between the APU current shunt and the EPCU, the digital display of the APU generator load indicator will show .00.

NOTE: The WARN caution light will not illuminate if the PWR switch is not set. The GEN OHT caution light on the APU control panel illuminates when the APU DC starter/generator temperature is more than 166°C (330°F). © Jazz Aviation LP Rev. 1.0 - Jan/2011





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DC EXTERNAL POWER SYSTEM The DC external power system supplies 28 VDC electrical power to the main 28 VDC generation system. 28 VDC electrical power is supplied through a DC external power receptacle to let an external power source energize the main 28 VDC generation system when the aircraft is on the ground and the engines are not operating.

The DC external system has protective functions to prevent damage to the system The DC external power is continuously monitored for the fault conditions that follow: ●●Correct polarity ●●Over voltage ●●Under voltage. The faults are isolated to give continued operation.

DC external power supplies 28 VDC electrical power through a line contactor to the left DC electrical load distribution systems. The EPCU controls the line contactor. The toggle switches on the DC CONTROL panel give manual control of the DC external power system.

Description The DC external power operates when the conditions are as follows: ●●BATTERY MASTER toggle switch is set to energize the EPCU ●●DC external power is set. External power contactor Kg is energized by the EPCU and DC starter/generator contactors K1 and K2 are prevented from operating as well as APU contactor K26.





Figure 22 – DC External - Schematic FOR TRAINING PURPOSES ONLY

Page 49

ATA 24 - ELECTRICAL POWER DC External Power Receptacle The DC external power receptacle is located in the left nose fuselage. The DC external power receptacle is a high power electrical connector. The unit has two large gauge pins to carry the DC current and one smaller pin for interface control.

Controls and Indications The DC CONTROL panel has the EXT PWR control for the DC external power system. OVERHEAD CONSOLE The DC external power is connected to the DC buses when: ●●Good external DC power is connected to the aircraft ●●The BATTERY MASTER toggle switch on the DC CONTROL panel is set ●●The EXT PWR toggle switch on the DC CONTROL panel is set.





Figure 23 – DC EXT. Power - Control & Receptacle FOR TRAINING PURPOSES ONLY

Page 51

ATA 24 - ELECTRICAL POWER EIS DC External Power Indications The MFD ELECTRICAL system page has a DC external power message. The EIS ELECTRICAL systems page shows a DC EXT PWR ON message when the: ●●DC external power voltage is more than 22 VDC and less than 31 VDC ●●DC EXT PWR toggle switch is set ●●DC external power is energizing the left and right buses.





Figure 24 – EIS Indication - DC External Power FOR TRAINING PURPOSES ONLY

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DC ELECTRICAL LOAD DISTRIBUTION 28 VDC electrical power is distributed through the circuit breaker panels in the flight compartment to services. Some distribution is done at the standby battery and DC contactor boxes.

Description 28 VDC electrical power is supplied through circuit breakers in the DC contactor box to the left and right 28 VDC circuit breaker panels. The left and right 28 VDC circuit breaker panels supply power to the avionics circuit breaker panel. 28 VDC electrical power is supplied through circuit breakers in the standby contactor box to the left and right 28 VDC circuit breaker panel and main hydraulic system NO.3. ●●The DC electrical load distribution system are the: ●●28 VDC circuit breaker panels ●●28 VDC avionics circuit breaker panel.





Figure 25 – DC Electrical Load Distribution FOR TRAINING PURPOSES ONLY

Page 55

ATA 24 - ELECTRICAL POWER 28 VDC Circuit Breaker Panels The left and right 28 VDC circuit breaker panel is installed in the flight compartment on the left and right side of the pilot’s and copilot’s seats. CAUTION: DO NOT LET THE CIRCUIT BREAKER PANEL TOUCH THE ADJACENT SIDE WINDOW. WHEN YOU INSTALL THE CIRCUIT BREAKER PANEL, IT IS EASY TO PUT A SCRATCH IN THE SIDE WINDOW. THIS WILL CAUSE DAMAGE TO THE SIDE WINDOW.





Figure 26 – Left & Right DC Circuit Breaker Panels FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER 28 VDC Avionics Circuit Breaker Panel The DC avionics circuit break r panel is installed in the flight compartment above and aft of the left 28 VDC circuit breaker panel. CAUTION: DO NOT LET THE CIRCUIT BREAKER PANEL TOUCH THE ADJACENT SIDE WINDOW. WHEN YOU INSTALL THE CIRCUIT BREAKER PANEL, IT IS EASY TO PUT A SCRATCH IN THE SIDE WINDOW. THIS WILL CAUSE DAMAGE TO THE SIDE WINDOW. The DC avionics circuit breaker panel gives distribution for the main 28 VDC generation system.





Figure 27 – 28 VDC Avionics C/B Panel FOR TRAINING PURPOSES ONLY

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AC VARIABLE FREQUENCY SYSTEM The AC variable frequency system supplies 115 VAC three-phase electrical power to the AC electrical load distribution system. The AC variable frequency system supplies electrical power to AC systems that are not frequency sensitive, such as: ●●De-icing (heaters) ●●Fuel (auxiliary pumps) ●●Hydraulic (standby power unit) ●●Galleys. The AC variable frequency system also interfaces with the Main 28 VDC generation system to supply electrical power to the transformer rectifier units (TRUs) that are additional sources of DC electrical power.

Description The AC variable frequency system has a left and right system with cross-tie capabilities. Two engine driven AC generators supply 115 VAC three-phase electrical power through AC generator line contactors to the left and right AC electrical load distribution systems.

and controls the AC generator line contactors. The AC variable frequency system also has current transformers in the AC contactor boxes and AC generators to measure A, B, and C phase current. The toggle switches on the AC CONTROL panel give manual control of the AC variable frequency system. NOTE: 115 VAC three-phase electrical power is also supplied through an AC external power receptacle to let an external power source energise the AC variable frequency system when the aircraft is on the ground and the engines are not operating The AC variable frequency system units are the: ●●AC generators ●●AC generator adapter plate ●●AC GCU ●●AC CONTROL panel ●●AC contactor boxes ●●AC contactor box contactors. The MFD, ELECTRICAL system page and the CAWP show AC variable frequency system indications.

It is not possible to connect the two AC generators in parallel. The AC generator line contactors have a centre off position to make sure that the AC generator is disconnected before it is connected to the opposite side (break before make). This is necessary because variable frequency AC generators are used. The AC GCUs regulate its related AC generator’s output voltage © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 28 – AC Variable Frequency System FOR TRAINING PURPOSES ONLY

Page 61

ATA 24 - ELECTRICAL POWER The alternating current variable frequency system modes of operation are: ●●Airborne (normal) ●●External AC power. The AC variable frequency system operates in the normal mode when: ●●Two engines are operating and the propeller is not feathered ●●External AC power is not set ●●GEN 1 and GEN 2 toggle switches on the AC CONTROL panel are set. The AC generators are by monitored by the AC GCUs to automatically control the operation of the AC generator line contactors. If a fault is sensed, the AC generator line contactors are opened or closed to automatically reconfigure the system. The fault is isolated from the remaining part of the AC variable frequency system to give continued operation. The AC variable frequency system has protective functions to prevent damage to the AC generators when there is a fault. The AC variable frequency system continuously monitors for the following fault conditions: ●●Source ●●Bus.

active protection. Circuit breakers and fuses are used for passive protection. The AC GCUs are used to control the AC generator line contactors for active protection. The AC variable frequency system uses the EPCU for CBIT. The AC variable frequency system also uses AC GCUs for initiated built in test. During the normal mode of operation, the AC GCU controls the related AC generator line contactor to connect the AC generator to the related AC bus. NOTE: The two AC GCUs monitor the condition of the opposite AC GCU. When an AC GCU senses that the opposite AC generator is not serviceable, it then controls the AC generator line contactor to connect the bus to the serviceable AC generator. The galley load shed contactors are controlled by auxiliary contacts in the AC generator line contactors. The two galley load shed contactors are automatically closed when the AC buses are energized by the two AC generators or external power.

The source and bus faults are isolated and the part of the system that continues to operate is automatically reconfigured to give continued operation. The AC variable frequency system has passive protection and © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 29 – AC Generation - Normal Operation FOR TRAINING PURPOSES ONLY

Page 63

ATA 24 - ELECTRICAL POWER AC Generators The AC generators are attached to the propeller reduction gearboxes of the engines with V-clamps around the quick attach/detach (QAD) adapter plates and the AC generator mounting flanges. The QAD adapters stay attached to the reduction gearboxes. CAUTION: YOU MUST CORRECTLY ALIGN THE FLANGE OF THE AC GENERATOR WITH THE QAD ADAPTER PLATE. IF YOU DO NOT DO THIS, YOU CANNOT INSTALL THE V BAND CLAMP AND YOU CAN CAUSE DAMAGE TO THE EQUIPMENT. The generator receives a supply of pressurized oil from the reduction gearbox to cool and lubricate the internal components. Oil is transferred from the gearbox, through the QAD adapter, to the generator using transfer tubes. These tubes are sealed with O-rings at each end to prevent oil leakage. Oil enters the shaft and is sprayed outward to cool the windings and lubricate the bearings. The used cooling oil then goes under gravity to the bottom of the generator where it is collected in the sump. A scavenge port is located in the sump. The engine scavenge pump extracts the oil and returns it to the engine. The generator is a three-stage machine, with electromagnetic coupling between stages. (It does not have slip rings and brushes). Each stage in the machine has of a rotor and stator segment along its length. The rotor is supported in the machine by ball bearings at both ends. The bearings are lubricated and cooled by © Jazz Aviation LP Rev. 1.0 - Jan/2011

the generator cooling oil. Inputs and outputs of the stator windings are supplied through interface connections on the body of the AC generator. The low current connections are made with a circular connector and the high power three-phase output connections are made with studs attached to a terminal block. A bonding stud is also attached to housing of the AC generator. The generator also has a bimetallic temperature sensor that closes a set of contacts and gives continuity through two pins on the interface connector when the temperature of the machine is too much. A three-phase current transformer is attached in the neutral lines of the windings to give current data to the AC GCU. NOTE: The AC generators output rating is 45 KVA. The first stage of the AC generator is a Permanent Magnet Generator (PMG). It has a magnet to make output power without the need for an external excitation sources. The three-phase output from the PMG is supplied through the AC GCU to the second stage field. The second stage is the exciter. NOTE The generator also has a generator positive voltage output signal so that the terminal voltage of each phase at the generator can be monitored by the EPCU for CBIT functions.




Figure 30 – AC Generator FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER AC Generator Adapter Plate There are two quick attach/detach QAD adapter plates installed on the aircraft, one for each AC generator. The QAD adapter plate is not removed when an AC generator is removed. The QAD adapter plate has two transfer tubes to supply engine oil to the AC generator. The QAD adapter plate has an O-ring and the transfer tubes also have O-rings and retaining clips. The QAD adapter plate gives an interface between the AC generators and the reduction gearbox of the engines.

AC Generator Control Units (GCU) The two AC GCUs are installed under the fuselage floor in the centre of the aircraft. The AC GCU is a fully enclosed, non-hermetically sealed unit. A connector is attached to one end of the AC GCU enclosure to interface with the electrical power generation and distribution system (EPGDS). The AC GCU has an Initiated Built In Test (lBIT) function to check the status of the unit. The unit is cooled by conduction through the chassis and support bracket and by convection air over the surface of the box. Power dissipating components in the unit are attached to chassis heat sinks to minimize the thermal resistance of the cooling circuit and give correct operating temperatures.


The AC GCUs give the functions that follow: ●●Voltage regulation ●●Control of the AC generator line contactors ●●Protection ●●Control of the AC generator and AC bus caution lights ●●CBIT. Voltage Regulation The AC GCU supplies power through a voltage regulator circuit to the exciter windings of the AC generator to start generator output when the conditions are as follows: ●●The related GEN 1 or GEN 2 toggle switch on the AC CONTROL panel is set ●●AC GCU senses that the AC generator is at the correct operating speed. The voltage regulator gives a constant voltage at the POR under different load and speed conditions. An average of the individual three-phase outputs are used for regulation. The AC GCU also uses current transformers in the system to continuously monitor the AC generator current and limit the current if the output is more than the permitted limits. Control Of The AC Generator Line Contactor When a stable output is sensed by the AC GCU, it closes the related AC generator line contactor to connect the AC generator to the related AC bus. It closes the opposite AC generator line contactor to connect the AC generator to the opposite AC bus if the opposite AC GCU or AC generator is not operating. Page 66 FOR TRAINING PURPOSES ONLY



Figure 31 – AC GCU Location FOR TRAINING PURPOSES ONLY

Page 67

ATA 24 - ELECTRICAL POWER The operating AC GCU senses this condition through a TRANSFER REQUEST [TR] signal. This signal is active when there is no need for transfer and is removed when there is a need. If AC external power is supplied to the aircraft, a signal is supplied to the AC GCU to energize the Y coil of the AC generator line contactor to give external AC power system operation. Protection To prevent damage to the AC generators, the AC GCUs have the protective functions that follow: ●●Overvoltage ●●Undervoltage ●●Differential current ●●Underfrequency ●●Bus fault. Overvoltage The AC generator is de-energized and the related line contactor is opened by the AC GCU before the voltage is more than approximately 125 VAC. This protective function is sensed in a period of time that is inversely proportional to the size of the sensed overvoltage condition.

NOTE: If an undervoltage and bus fault condition is sensed at the same time, the overcurrent protection function will occur. Differential Current The AC generator is de-energized and the related AC generator line contactor is opened by the AC GCU when the differential current on any phase is more than 20 A. Underfrequency The AC generator is de-energized and the related AC generator line contactor is opened by the AC GCU when the AC generator frequency is less than 300 Hz. It will automatically reconnect the AC generator when the frequency is more than 320 Hz. This will occur only if the system was not previously disconnected by a different protective function. As the AC generator frequency goes below 340 Hz, the output voltage decreases relative to the frequency until the AC generator is disconnected at 300 Hz NOTE: When the condition lever is set to START & FEATHER, the AC generator is de-energized and disconnected from the bus because the AC generator speed to too low for operation. The AC generator will automatically reconnect.

Undervoltage The AC generator is de-energized and the related line contactor is opened by the AC GCU before the voltage is less than approximately 100 VAC. © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 32 – AC GCU


ATA 24 - ELECTRICAL POWER AC Control Panel The AC CONTROL panel is attached to the overhead console with four DZUS fasteners. The toggle switches are identified as: ●●GEN 1 ●●GEN 2 ●●EXT POWER. The three switches have an OFF label to show their off position. The AC CONTROL panel gives manual control of the AC variable frequency system.





Figure 33 – AC Control Panel FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER AC Contactor Boxes K1 and K3 are installed in the left-hand side ACCB, and K2 and K4 are installed in the right-hand side ACCB. Also, when installed, K5 is in the left ACCB and K6 is in the right ACCB. CT1, CT3, and CT5 are installed in the left-hand side ACCB, and CT2, CT4, and CT6 are installed in the right-hand side ACCB. Connectors are attached to the enclosure to interface with the EPGDS.

output current of the AC generators to the EPCU for AC electrical load indications in the electronic instrument system (EIS). Two current transformers, identified as CT2 and CT5, supply total generator output current of the AC generators to the AC GCUs for differential current sensing (protection). When an AC bus is energized by the opposite AC generator, CT3 or CT6 is also used.

There are two ACCBs installed on the aircraft. The units have additional components: ●●AC generator line contactors, K1 and K2 ●●External power contactors, K3 and K4 ●●Galley load shed contactors, K5 and K6 (optional) ●●Stand by power unit (SPU) contactor, installed in the right hand side ACCB ●●Internal cable assemblies and rigid bus bars ●●Circuit breakers and fuses for output protection ●●Circuit breakers for heaters in the propellers anti-icing system ●●Current transformers, CT1, CT2, CT3, CT4, CT5, CT6. ●●External Power Protection Unit (EPPU), installed in the right-hand side ACCB The current transformers in the ACCBs monitor the current for phase A, B, and C of the AC generator for indication and protection. Two current transformers, identified as CT1 and CT4, supply total generator © Jazz Aviation LP Rev. 1.0 - Jan/2011




Figure 34 – AC Contactor Box (ACCB) FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER AC Contactor Box Contactors The contactors in the left-hand side and right-hand side ACCBs attach directly to rigid bus bars. AC Generator Line Contactors The AC generator line contactors, K1 and K2, are 150A Three-Pole Double Throw (3PDT), centre off contactors. They have two coil windings, identified as X and Y, to move the contact arms to connect the AC buses to the related or the opposite AC generator. They also have auxiliary contacts to control the galley load shed contactors, K5 and K6. NOTE: The contactor arms also move to the Y position when the external AC power is used. NOTE: The X position of the bus contactor is controlled by the related AC GCU and the Y position is controlled by the opposite AC GCU.

They also have auxiliary contacts to control the galley load shed contactors, K5 and K6. Galley Load Shed Contactors The galley load shed contactors, K5 and K6, are 50A Three-Pole Single Throw (3PST), normally open contactors. They have one coil winding to move the contact arms to connect the galley buses to the AC buses. The galley load shed contactors are only energized when: ●●The two AC buses are energized by the two AC generators ●●The two AC buses are energized by the external AC power.

External Power Contactors The external power contactor, K3 and K4, are 100A 3PDT, contactors. They have one coil winding to move the contact arms to connect the AC buses to the AC external power receptacle. The external power contactors are only energized when the conditions are as follows: ●●Good external AC power is supplied ●●EXT PWR toggle switches on the AC CONTROL panel are set





Figure 35 – ACCB Contactors FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER Controls And Indication The AC CONTROL panel has the controls for the AC variable frequency system: ●●GEN 1 toggle switch ●●GEN2 toggle switch. The AC generators are connected to the AC buses when the: ●●Two engines are operating and the propeller is not feathered, ●●EXT PWR toggle switch power is not set, and ●●GEN1 and GEN2 toggle switches are set. The GEN1 and GEN2 toggles switches are set to the OFF position to reset the related AC GCU. The MFD ELECTRICAL system page has an AC generator voltage and load indicator with a digital display for voltage and load. AC Voltage The voltage part of the AC generator voltage and load indicator shows an indication for the digital display of the AC generators phase A, B, and C. If there is an open or short circuit between the AC generator current transformer and the EPCU, the digital display of the AC generator load indicator will show .00. The numbers for the digital display of the AC generator voltage change from 0 to 249 in 1 volt increments.

If there is an open or short circuit to ground potential between the AC bus and the EPCU, the related digital display of the AC generator voltage will show 0. AC Load The load part of the AC generator voltage and load indicator shows an indication for the digital display of the AC generators phase A, B, and C. The numbers for the digital display of the AC generator load change from .00 to +1.99 in 0.01 power unit increments. A + symbol before the numbers shows an overload condition. The numbers relate to the AC generator load as a percentage of the maximum rate. AC GEN Caution Lights The #1 AC GEN or #2 AC GEN caution light illuminates when the associated generator (GEN1 or GEN2) is not connected to its bus. The #1 AC GEN or #2 AC GEN caution light will also illuminate for conditions that are not malfunctions as follows: ●●The AC GEN1 or AC GEN2 toggle switch is set to the ●●OFF position ●●External AC power is energizing the Land R AC buses. If a source fault is sensed, the AC generator line contactors K1 and K2 will not connect the AC GEN to the 115 VAC BUS.





Figure 36 – AC Control and Indications FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER AC BUS Caution Lights The R AC BUS or L AC BUS caution light illuminates when there is an overcurrent condition on the 115 VAC BUS for more than seven seconds. The caution light will go out if the associated toggle switch is set to the OFF position. AC GEN HOT Caution Lights The #1 AC GEN HOT or #2 AC GEN HOT caution light in the CAWP illuminates when the AC generator temperature is more than 166°C (330°F).





Figure 37 – Caution Lights FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER External Power Receptacle The AC external power receptacle is located in the right nose fuselage. The unit has four large gauge pins to carry the three-phase AC current and two smaller pins for interface control. It gives the interface connection between external AC power source and the aircraft.

External AC Power Protection Unit The external AC power protection unit is located in the right AC contactor box. It is attached with screws. The AC external power protection unit monitors the quality of the input power to the AC external power receptacle and prevents connection of the power to the aircraft distribution system if the power is not satisfactory. It monitors the parameters for: ●●Undervoltage, 106 VAC ●●Overvoltage, 124 VAC ●●Underfrequency, 370 Hz ●●Overfrequency, 450 Hz ●●Phase Rotation.





Figure 38 – AC External Power Receptacle and EPPU FOR TRAINING PURPOSES ONLY

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ATA 24 - ELECTRICAL POWER Controls And Indications The AC CONTROL panel has the EXT PWR control for the AC external AC power system. The external AC power is connected to the AC buses when the: ●●Good external AC power is connected to the aircraft, and ●●BATTERY MASTER toggle switch on the DC CONTROL panel is set, and ●●EXT PWR toggle switch on the AC CONTROL panel is set. The MFD ELECTRICAL system page has an AC external power message. The EIS ELECTRICAL systems page shows an AC EXT PWR ON message when: ●●AC external power voltage is more than 106 VAC and less than 124 VAC, frequency is more than 370 Hz and less than 450 Hz, phase rotation is phase A, phase B, then phase C, and AC EXT PWR toggle switch is set, and ●●AC external power is energizing the left and right 115 VAC buses.





Figure 39 – AC External Power - Controls and Indications FOR TRAINING PURPOSES ONLY

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ELECTRICAL LOAD DISTRIBUTION Three-phase, 115 VAC variable frequency electrical power is distributed through a circuit breaker panel in the flight compartment to electrical loads. Some distribution is done at the AC contactor boxes.

Description Phase A, phase B, and phase C 115 VAC electrical power is supplied through circuit breakers in the left and right AC contactor boxes to: ●●115 VAC variable frequency circuit breaker panel ●●Propellers anti-icing system ●●Main hydraulic system No.1. The AC electrical load distribution has an 115 VAC variable frequency circuit breaker panel. Circuit breakers (CB) in the 115 VAC variable frequency circuit breaker panel and AC contactor box protect the wires in the AC variable frequency system. 115 VAC Variable Frequency Circuit Breaker Panel The 115 VAC variable frequency circuit breaker panel is installed on the rear flight compartment bulkhead above and aft of the right 28 VDC circuit breaker panel. It has circuit breakers attached to the panel. Panel markings identify the buses and circuit breakers.

CAUTION: DO NOT LET THE CIRCUIT BREAKER PANEL TOUCH THE ADJACENT SIDE WINDOW. WHEN YOU INSTALL THE CIRCUIT BREAKER PANEL, IT IS EASY TO PUT A SCRATCH IN THE SIDE WINDOW. THIS WILL CAUSE DAMAGE TO THE SIDE WINDOW.

Operation Three-phase, 115 VAC variable frequency electrical power is supplied through three 50 A circuit breakers on the Land R AC contactor box to the 115 VAC variable frequency circuit breaker panel. Three-phase, 115 VAC variable frequency electrical power is supplied through three 35 A circuit breakers on the L and R AC contactor box to the propellers anti-icing system Three-phase, 115 VAC variable frequency electrical power is supplied through three 60 A circuit breakers on the R AC contactor box to the main hydraulic systems 1 NOTE: The left part of the AC electrical load distribution is described. The right part is similar.





Figure 40 – AC Distribution FOR TRAINING PURPOSES ONLY

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ATA24 bombardier q400 electrical power

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