Speed Control of 3 Phase Ac Induction Motor Using Micro 2407

SPEED CONTROL OF 3 PHASE AC INDUCTION MOTOR USING MICRO 2407 AND VPET - 106

REVISION 2.5 01.05.2011

Vi Microsystems Pvt. Ltd., Plot No. 75, Electronics Estate, Perungudi, Chennai – 600 096. Ph : 91 - 44 - 2496 1852 , 91- 44 - 2946 3142, Fax : 91- 44 - 2496 1536. Mail : [email protected] Web : www.vimicrosystems.com

CONTENTS 1.

INTRODUCTION

1

2.

3 PHASE AC INDUCTION MOTOR

1

3.

SPEED SENSOR

8

4.

CONNECTOR DETAILS

16

5.

MOTOR SPECIFICATIONS

17

6.

MICRO – 2407

18

7.

HARDWARE DESCRIPTION OF MICRO 2407

21

8.

VPET-106A

29

9.

WIRING DIAGRAM

35

10.

EXPERIMENTS

36

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A 1. INTRODUCTION Due to the advancement in switching power devices, the Solid-state drives are now becoming more and more popular in many Industrial applications. For efficient control of those drives, the frequency and magnitude of the voltage has to be controlled. The control of frequency and voltage can be done through different methods. Among the different available methods, Pulse width modulation (PWM) technique is the most commonly employed method for controlling the drives. The width of the PWM can be varied according to the modulating signal. By varying the duty cycle of switching pulses, applied to the Power devices, the turn ON and turn OFF interval gets varied from one pulse period to another. By doing so we are modulating the widths of the pulses. Suppose the pulse width is varied from the center of the period then it is called as Symmetrical PWM and if the width is varied from any edge of the period then it is called as Asymmetrical PWM. Thus by controlling the PWM pulses, applied to the Power converters the frequency and magnitude of the voltage can be varied as per the requirement. This helps in improving the performance and efficiency of the machine. Due to the advantage of independent voltage and frequency control with the PWM method, the scalar and vector control of the AC Induction Motor is made possible. The forth coming chapters will explain about the implementation of scalar or V/F control of three phase AC Induction Motor using Micro2407 DSP Trainer Kit. 2. THREE PHASE AC INDUCTION MOTOR AC Induction motors are the most common motors used in industrial motion control systems, as well as in main powered home appliances. Simple and rugged design, low-cost, low maintenance and direct connection to an AC power source are the main advantages of AC Induction motors. Various types of AC Induction motors are available in the market. Different motors are suitable for different applications. Although AC Induction motors are easier to design than DC motors, the speed and the torque control in various types of AC Induction motors require a greater understanding of the design and the characteristics of these motors. 2.1 Basic Construction and Operating Principle Like most motors, an AC Induction motor has a fixed outer portion, called the stator and a rotor that spins inside with a carefully engineered air gap between the two. Virtually all electrical motors use magnetic field rotation to spin their rotors. A three-phase AC Induction motor is the only type where the rotating magnetic field is created naturally in the stator because of the nature of the supply. DC motors depend either on mechanical or electronic commutation to create rotating magnetic fields. A single-phase AC Induction motor depends on extra electrical components to produce this rotating magnetic field.

Vi Microsystems Pvt. Ltd.,

[1]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A Two sets of electromagnets are formed inside any motor. In an AC Induction motor, one set of electromagnets is formed in the stator because of the AC supply connected to the stator windings. The alternating nature of the supply voltage induces an Electromagnetic Force (EMF) in the rotor (just like the voltage is induced in the transformer secondary) as per Lenz’s law, thus generating another set of electromagnets; hence the name – Induction motor. Interaction between the magnetic field of these electromagnets generates twisting force, or torque. As a result, the motor rotates in the direction of the resultant torque. Stator The stator is made up of several thin laminations of aluminum or cast iron. They are punched and clamped together to form a hollow cylinder (stator core) with slots as shown in Figure 1. Coils of insulated wires are inserted into these slots. Each grouping of coils, together with the core it surrounds forms an electromagnet (a pair of poles) on the application of AC supply. The number of poles of an AC Induction motor depends on the internal connection of the stator windings. The stator windings are connected directly to the power source. Internally they are connected in such a way, that on applying AC supply, a rotating magnetic field is created.

Figure-1 Typical Stator Rotor The rotor is made up of several thin steel laminations with evenly spaced bars, which are made up of aluminum or copper, along the periphery. In the most popular type of rotor (squirrel cage rotor), these bars are connected at ends mechanically and electrically by the use of rings. Almost 90% of Induction motors have squirrel cage rotors. This is because the squirrel cage rotor has a simple and rugged construction. The rotor consists of a cylindrical laminated core with axially placed parallel slots for carrying the conductors. Each slot carries a copper, aluminum, or alloy bar. These rotor bars are permanently short-circuited at both ends by means of the end rings, as shown in Figure 2.


[2]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A This total assembly resembles the look of a squirrel cage, which gives the rotor its name. The rotor slots are not exactly parallel to the shaft. Instead, they are given a skew for two main reasons.

Figure-2 Squirrel Cage Rotor The first reason is to make the motor run quietly by reducing magnetic hum and to decrease slot harmonics. The second reason is to help reduce the locking tendency of the rotor. The rotor teeth tend to remain locked under the stator teeth due to direct magnetic attraction between the two. This happens when the number of stator teeth is equal to the number of rotor teeth. The rotor is mounted on the shaft using bearings on each end; one end of the shaft is normally kept longer than the other for driving the load. Some motors may have an accessory shaft on the nondriving end for mounting speed or position sensing devices. Between the stator and the rotor, there exists an air gap, through which due to Induction, the energy is transferred from the stator to the rotor. The generated torque forces the rotor and then the load to rotate. Regardless of the type of rotor used, the principle employed for rotation remains the same. 2.2 Speed of an Induction Motor The magnetic field created in the stator rotates at a synchronous speed (NS).

Where, Ns = the synchronous speed of the stator magnetic field in RPM P = the number of poles on the stator F = the supply frequency in Hertz The magnetic field produced in the rotor because of the induced voltage is alternating in nature. To reduce the relative speed, with respect to the stator, the rotor starts running in the same direction as that of the stator flux and tries to catch up with the rotating flux. However, in practice, the rotor never succeeds in “catching up” to the stator field. The rotor


[3]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A runs slower than the speed of the stator field. This speed is called the Base Speed (Nb). The difference between Ns and Nb is called the slip. The slip varies with the load. An increase in load will cause the rotor to slow down or increase slip. A decrease in load will cause the rotor to speed up or decrease slip. The slip is expressed as a percentage and can be determined with the following formula:

where Ns = the synchronous speed in RPM Nb = the base speed in RPM 2.3 Types of Induction Motor Three-phase AC Induction motors are widely used in industrial and commercial applications. They are classified either as squirrel cage or wound-rotor motors. These motors are selfstarting and use no capacitor, start winding, centrifugal switch or other starting device. They produce medium to high degrees of starting torque. The power capabilities and efficiency in these motors range from medium to high compared to their single-phase counterparts. Popular applications include grinders, lathes, drill presses, pumps, compressors, and conveyors, also printing equipment, farm equipment, electronic cooling and other mechanical duty applications. Squirrel Cage Motor Almost 90% of the three-phase AC Induction motors are of this type. Here, the rotor is of the squirrel cage type and it works as explained earlier. The power ratings range from one-third to several hundred horsepower in the three-phase motors. Motors of this type, rated one horsepower or larger, cost less and can start heavier loads than their single-phase counterparts. Wound-Rotor Motor The slip-ring motor or wound-rotor motor is a variation of the squirrel cage Induction motor. While the stator is the same as that of the squirrel cage motor, it has a set of windings on the rotor, which are not short-circuited, but are terminated to a set of slip rings. These are helpful in adding external resistors and contactors. The slip necessary to generate the maximum torque (pull-out torque) is directly proportional to the rotor resistance. In the slipring motor, the effective rotor resistance is increased by adding external resistance through the slip rings. Thus, it is possible to get higher slip and hence, the pull-out torque at a lower speed. A particularly high resistance can result in the pull-out torque occurring at almost zero speed,


[4]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A providing a very High pull-out torque at a low starting current. As the motor accelerates, the value of the resistance can be reduced, altering the motor characteristic to suit the load requirement. Once the motor reaches the base speed, external resistors are removed from the rotor. This means that now the motor is working as the standard Induction motor. This motor type is ideal for very high inertia loads, where it is required to generate the pull-out torque at almost zero speed and accelerate to full speed in the minimum time with minimum current draw. 2.4 Torque Equation Governing Motor Operation The motor load system can be described by a fundamental torque equation.

where, T = the instantaneous value of the developed motor torque (N-m or lb-inch) Tl = the instantaneous value of the load torque (N-m or lb-inch) ? m = the instantaneous angular velocity of the motor shaft (rad/sec) J = the moment of inertia of the motor – load system (kg-m 2 or lb-inch 2) For drives with constant inertia, (dJ/dt) = 0. Therefore, the equation would be:

This shows that the torque developed by the motor is counter balanced by a load torque, Tl and a dynamic torque, J(d? m/dt). The torque component, J(d? /dt), is called the dynamic torque because it is present only during the transient operations.


[5]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A

Figure-3 Typical Torque-Speed Curve of 3-Phase AC Induction Motor The drive accelerates or decelerates depending on whether T is greater or less than Tl. During acceleration, the motor should supply not only the load torque, but also an additional torque component, J(d? m/dt), in order to overcome the drive inertia. In drives with large inertia, such as electric trains, the motor torque must exceed the load torque by a large amount in order to get adequate acceleration. In drives requiring fast transient response, the motor torque should be maintained at the highest value and the motor load system should be designed with the lowest possible inertia. The energy associated with the dynamic torque, J(d? m/dt), is stored in the form of kinetic energy(KE) given by, J(? m2/2). During deceleration, the dynamic torque, J(d? m/dt), has a negative sign. Therefore, it assists the motor developed torque T and maintains the drive motion by extracting energy from the stored kinetic energy. To summarize, in order to get steady state rotation of the motor, the torque developed by the motor (T) should always be equal to the torque requirement of the load (Tl). The torque-speed curve of the typical three-phase Induction motor is shown in Figure-3.

2.5 Speed Control Techniques


[6]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A Various speed control techniques implemented by modern-age VFD are mainly classified in the following three categories: •Scalar Control (V/f Control) 2.5.1 V/f CONTROL As we can see in the speed-torque characteristics, the Induction motor draws the rated current and delivers the rated torque at the base speed. When the load is increased (over-rated load), while running at base speed, the speed drops and the slip increases. As we have seen in the earlier section, the motor can take up to 2.5 times the rated torque with around 20% drop in the speed. Any further increase of load on the shaft can stall the motor. The torque developed by the motor is directly proportional to the magnetic field produced by the stator. So, the voltage applied to the stator is directly proportional to the product of stator flux and angular velocity. This makes the flux produced by the stator proportional to the ratio of applied voltage and frequency of supply. By varying the frequency, the speed of the motor can be varied. Therefore, by varying the voltage and frequency by the same ratio, flux and hence, the torque can be kept constant throughout the speed range. Stator Voltage (V) % [Stator Flux (? ) x [Angular Velocity (T)] V % ? x 2 Bf ? % V/f

This makes constant V/f the most common speed control of an Induction motor. Figure 3 shows the relation between the voltage and torque versus frequency. Figure 5 demonstrates voltage and frequency being increased up to the base speed. At base speed, the voltage and frequency reach the rated values as listed in the nameplate. We can drive the motor beyond base speed by increasing the frequency further. However, the voltage applied cannot be increased beyond the rated voltage. Therefore, only the frequency can be increased, which results in the field weakening and the torque available being reduced. Above base speed, the factors governing torque become complex, since friction and windage losses increase significantly at higher speeds. Hence, the torque curve becomes nonlinear with respect to speed or frequency.


[7]


Figure-4 Speed-Torque Characteristics with V/F Control 3. SPEED SENSOR Motor speed is sensed from the following methods. 1. Optical Encoder 2. Quadrature Encoder Pulse 3. Proximity sensor 3.1 OPTICAL ENCODER Circular windows around the circular disk mounted on the motor shaft such that it rotates with the shaft. A LED is mounted on the one side of the disk and a phototransistor is mounted on the other side of the disk, opposite to the LED, the following figure-5 shows the speed sensor

Figure-5 Optical Encoder Speed Sensor During rotation when circular window come across the LED. The light passes to the phototransistor. As a result, phototransistor conducts and produces low output at its collector.


[8]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A Each time when light passes through window to the phototransistor, it conducts and output goes low, otherwise phototransistor is off and output is high.

Figure-6 Schematic view of Optical Speed Sensor As disk rotates the trains of pulses are generated. The number of pulses in one rotation equals the number of circular windows on the disk. Therefore by counting number of pulses we can decide the position of the shaft as well as number of rotations performed by the shaft. By counting the number of rotations in specific time we can also calculate the speed of rotation. Counting the number of pulses in specific time, these pulses convert frequency to voltage by using frequency to voltage converter. 3.2 QUADRATURE ENCODER PULSE i. Introduction The enhanced quadrature encoder pulse (eQEP) module is used for direct interface with a linear or rotary incremental encoder to get position, direction, and speed information from a rotating machine for use in a high-performance motion and position-control system. A single track of slots patterns the periphery of an incremental encoder disk, as shown in Figure-7. These slots create an alternating pattern of dark and light lines. The disk count is defined as the number of dark/light line pairs that occur per revolution (lines per revolution). As a rule, a second track is added to generate a signal that occurs once per revolution (index signal: QEPI), which can be used to indicate an absolute position. Encoder manufacturers identify the index pulse using different terms such as index, marker, home position, and zero reference


[9]


Figure-7 Optical Encoder Disk To derive direction information, the lines on the disk are read out by two different photoelements that “look” at the disk pattern with a mechanical shift of 1/4 the pitch of a line pair between them. This shift is realized with a reticle or mask that restricts the view of the photoelement to the desired part of the disk lines. As the disk rotates, the two photo-elements generate signals that are shifted 90° out of phase from each other. These are commonly called the quadrature QEPA and QEPB signals. The clockwise direction for most encoders is defined as the QEPA channel going positive before the QEPB channel and vice versa as shown in Figure-8. The encoder wheel typically makes one revolution for every revolution of the motor or the wheel may be at a geared rotation ratio with respect to the motor. Therefore, the frequency of the digital signal coming from the QEPA and QEPB outputs varies proportionally with the velocity of the motor. For example, a 2000-line encoder directly coupled to a motor running at 5000 revolutions per minute (rpm) results in a frequency of 166.6 KHz, so by measuring the frequency of either the QEPA or QEPB output, the processor can determine the velocity of the motor.

Figure 8 QEP Encoder Output Signal for Forward/Reverse Movement ii. QEP Inputs


[ 10 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A The eQEP inputs include two pins for quadrature-clock mode or direction-count mode, an index (or 0 marker), and a strobe input. QEPA/XCLK and QEPB/XDIR These two pins can be used in quadrature-clock mode or direction-count mode. Quadrature-clock Mode The eQEP encoders provide two square wave signals (A and B) 90 electrical degrees out of phase whose phase relationship is used to determine the direction of rotation of the input shaft and number of eQEP pulses from the index position to derive the relative position information. For forward or clockwise rotation, QEPA signal leads QEPB signal and vice versa. The quadrature decoder uses these two inputs to generate quadrature-clock and direction signals. Direction-count Mode In direction-count mode, direction and clock signals are provided directly from the external source. Some position encoders have this type of output instead of quadrature output. The QEPA pin provides the clock input and the QEPB pin provides the direction input. QEPI: Index or Zero Marker The eQEP encoder uses an index signal to assign an absolute start position from which position information is incrementally encoded using quadrature pulses. This pin is connected to the index output of the eQEP encoder to optionally reset the position counter for each revolution. This signal can be used to initialize or latch the position counter on the occurrence of a desired event on the index pin. iii. Two Channel Optical Encoders

Figure-9 Two channel Quadrature Encoder pulse Description


[ 11 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A The HEDM-5605 is high performance, low cost, two channel optical incremental encoders as shown in figure-9. These encoders emphasize high reliability, high resolution, and easy assembly. Each encoder contains a lensed LED source, an integrated circuit with detectors and output circuitry, and a codewheel that rotates between the emitter and detector IC. The outputs of the HEDM- 5605 are two square waves in quadrature. This index output is a 90 electrical degree, high true index pulse that is generated once for each full rotation of the codewheel. The HEDS series utilizes metal codewheels, while the HEDM series utilizes a film codewheel allowing for resolutions to 1024 CPR. These encoders may be quickly and easily mounted to a motor. For larger diameter motors, the HEDM-5605 feature external mounting ears. The quadrature signals and the index pulse are accessed through five 0.025 inch square pins located on 0.1 inch centers. Working Operation The HEDM-5605 translates the rotary motion of a shaft into either a two- digital output. As seen in figure-10, these encoders contain a single Light Emitting Diode (LED) as its light source. The light is collimated into a parallel beam by means of a single polycarbonate lens located directly over the LED. Opposite the emitter is the integrated detector circuit. This IC consists of multiple sets of photodetectors and the signal processing circuitry necessary to produce the digital waveforms. The codewheel rotates between the emitter and detector, causing the light beam to be interrupted by the pattern of spaces and bars on the codewheel. The photodiodes, which detect these interruptions, are arranged in a pattern that corresponds to the radius and design of the codewheel. These detectors are also spaced such that a light period on one pair of detectors corresponds to a dark period on the adjacent pair of detectors. The photodiode outputs are then fed through the signal processing circuitry resulting in A, A, B and B. Comparators receive these signals and produce the final outputs for channels A and B. Due to this integrated phasing technique, the digital output of channel A is in quadrature with that of channel B (90 degrees out of phase). In the HEDS-5540 and 5640, the output of the comparator for I and I is sent to the index processing circuitry along with the outputs of channels A and B.


[ 12 ]


Figure-10 Block diagram for QEP (HEDM-5605) The final output of channel I is an index pulse PO which is generated once for each full rotation of the codewheel. This output PO is a one state width (nominally 90 electrical degrees), high true index pulse that is coincident with the low states of channels A and B.


[ 13 ]


3.3 PROXIMITY SENSOR

Figure 11: Proximity sensor

FEATURES 1.

Inductive sensor, style: cylinder shape, diameter: 18mm.

2.

DC 2-wire (10-30V DC), DC 3-wire (10-30V DC), DC 4-wire (10-30V DC), AC 2wire (90-250V AC), *DC 2-wire (5V DC) also available

3.

Connection mode: 3/4 wire or 3/4 pin connector

4.

Mounting distance: shielded (5mm), unshielded (8mm)

5.

With LED operation indicate lamp, easily identifiable

6.

Brass chrome plated, proof of oil. water acid, alkaline

7.

Standard sensing object: iferrous metals

8.

Protection rate: IP67, water resistant

9.

Over-current protection

10.

Widely applied in measuring, Counting, Rpm measuring in mechanism, chemical, paper manufacture light industry, etc.


[ 14 ]


TECHNICAL SPECIFICATIONS SIZE TYPE OP. VOLTAGE MAX. LOAD CURRENT PROTECTION SENSING DISTANCE

M 18 INDUCTIVE, PNP, NO, NFM 5 - 40VDC 300mAmpere YES 8mm

ELECTRICAL CONNECTION

Figure 11: Electrical connection of Proximity sensor


[ 15 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A 4. CONNECTION DETAILS Quadrature Encoder Pulse Sensor

Figure-12 -9 pin ‘D’ connector for QEP Sensing ii. Optical Encoder Sensor

Figure-13 -9 pin “D” Connector for Optical Encoder Sensing PIN Details 1. Cathode 2. Anode 3. Collector 4. Emitter 5. No Connection 6. No Connection 7. No Connection 8. No Connection 9. No Connection


[ 16 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A 5. MOTOR SPECIFICATIONS

Number of poles : 4 Phase

: 3

Rated Power

: 0.75 KW

Rated Voltage

: 415 V (Star)

Rated Current

: 1.8 A

Supply frequency : 50 Hz Rated Speed

: 1395 rpm

Power Factor

: 0.81

Weight

: 14 Kg


[ 17 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A 6. MICRO - 2407 6.1. INTRODUCTION Micro-2407 is a 16-bit (data lines) fixed point DSP trainer, based on texas instruments TMS320LF2407A DSP Processor. This trainer enables the user to learn the basics of digital signal processing & digital control along with basic DSP functions like filtering, PWM generation and calculation of spectral characteristics of input analog signals. The trainer helps to perform real time implementation of very complex algorithms, such as adaptive control, Motor control etc. The TMS320LF2407A contains a C2xx DSP core along with useful peripherals such as ADC, Timer, PWM Generation are integrated onto a single piece of silicon. The Micro2407 trainer can be operated in two modes. In the mode: 1 (serial mode) the trainer is configured to communicate with PC through serial port. In the mode: 2 (stand alone mode), the user can interact with the trainer through the IBM PC keyboard and 16 × 2 LCD display. 6.2. SPECIFICATIONS 1. PROCESSOR CPU Crystal Frequency Clock Frequency Wait States

2. MONITOR (EPROM)

: Texas Instruments TMS320LF2407A, : 10MHz. : 40 MHz : 2 for EPROM, 0 for On-Chip RAM, 2 for external RAM and 6 for LCD DISPLAY : 0x0000 - 0xBFFF for 48kwords

3. MEMORY Program RAM Data RAM

: 0xC000 - 0xFFFF for 16kwords. : 0x9000 - 0xFFFF for 32kwords (0x8000 to 0x8FFF reserved for monitor).

4. SERIAL

: One RS232C Serial Interface using on-chip SERIAL COMMUNICATION INTERFACE (SCI) module

5. TIMER

: On-chip timer can be used.

6. INTERRUPTS

: 6 Interrupt lines of TMS320LF2407A are available to users.

7. IBM AT KEY BOARD

: CD 4015-101 KEY keyboard controller

8. DISPLAY

: 16x2 LCD display (For Mode-2).


[ 18 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A 9. ON-BOARD BATTERY BACKUP

: 3.6V, Ni-Cd Battery

10. POWER SUPPLY (LPOW-001A) SPECIFICATIONS Mains :

230 Volts AC at 50 Hz

Outputs:

1. + 5 Volts, 3.5 Amps Regulated 2. + 12 Volts, 150 mA Regulated 3. - 12 Volts, 150 mA Regulated 4. +5 Volts, 500 mA Regulated

11. SYSTEM POWER CONSUMPTION Digital + 5 V : 1.5 Amps + 12 V : 100 mA - 12 V : 100 mA Analog + 5 V : 200 mA 6.3 FEATURES OF TMS320C / F2XX 1. TMS320C / F2xx core CPU * 32-bit Central Arithmetic Logic Unit (CALU). * 32-bit accumulator. * 16-bit x 16-bit parallel multiplier with a 32-bit product capability. * Eight 16-bit auxiliary registers with a dedicated arithmetic unit for indirect addressing of data memory. 2. MEMORY * 64 kwords program memory space * 64 kwords Data memory space * 64 kwords I / O space 3. POWER * Static CMOS Technology * Four power-down modes to reduce power consumption. 4. EMULATION * IEEE standard 1149.1 test access port to on-chip scan-based emulation logic. 5. SPEED * 25-ns (40MIPS) instruction cycle time, with most instructions single cycle.


[ 19 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A 6. EVENT MANAGER * Two event managers A & B. * Four 16-bit general-purpose timers with six modes including continuous up counting and continuous down counting. * Six 16-bit full compare units with dead band capability in each event managers. * Two 16 bit Timer PWMs in each event manager. * Six capture units, four of which have quadrature encoder pulse interface capability. 7. DUAL 10-BIT ANALOG-TO-DIGITAL CONVERTER (ADC) 8. 40 INDIVIDUALLY PROGRAMMABLE, MULTIPLEXED I/O PINS. 9. PHASE-LOCKED LOOP (PLL) BASED CLOCK MODULE. 10. WATCHDOG TIMER MODULE WITH REAL-TIME INTERRUPT (RTI) 11. SERIAL COMMUNICATION INTERFACE (SCI) 12. SERIAL PERIPHERAL INTERFACE (SPI) 13. CAN CONTROLLER MODULE


[ 20 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A 7. HARDWARE DESCRIPTION OF MICRO 2407 7.1. FRONT PANEL DESCRIPTION This chapter gives a brief description about Front Panel of Micro-2407 Trainer board.

Figure - 14 Pictorial View of Micro-2407


[ 21 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A The following tabular column shows the component and the locations with reference to Micro-2407 Trainer Board.


[ 22 ]


Table – 1: Location of Components in Micro-2407 Board


[ 23 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A 7.2. CONNECTOR DETAILS 1. INTRODUCTION Following are the shortlist of connectors available on Micro-2407 trainer board. P1 - 5 Pin Unicon Connector P2 - 9 Pin Serial port Connector P3 - 2 Pin J801 Connector P4 - 40 Pin FRC Connector P5 - 14 Pin JTAG Connector P6 - 26 Pin FRC Connector P7 - J801 3 Pin Connector P8 - 34 Pin FRC Connector P9 - 6 Pin Keyboard Connector 2. POWER CONNECTOR: (P1) CONNECTOR USED Single row 5 Pin UNICON Male Connector - Spacing between pins 2,3,4,5 = 5mm - Spacing between pins 1&2 = 7.5mm PIN DETAILS

Table – 2: Signal Description of P1 Connector Where, NC - No Connection VCC - +5V Power Supply GND - 0V Reference Ground MATING CONNECTOR Single row 5-pin UNICON Female Connector - With the same spacing as said above


[ 24 ]


3. SERIAL PORT CONNECTOR: (P2) CONNECTOR USED 9 Pin D type Male Connector - Pins arranged in two rows of 5 and 4 pins - Grid pitch is 2.76 mm * 2.84 mm - The connector is AMPHENOL standard

Table – 3: Signal Description of P2 Connector SIGNAL DEFINITION TxD - Transmit Data RxD - Receive Data RTS - Ready to send CTS - Clear to send MATING CONNECTOR 9 Pin D type Female Connector with the same specifications. 4. J801 2 PIN CONNECTOR (P3) PIN CONFIGURATION 1 - GND 2 - +5v 5. GENERAL PURPOSE INPUT / OUTPUT CONNECTOR (P4) CONNECTOR USED

: 40 Pin Dual row male header

MATING CONNECTOR

: 40 Pin Dual row female Socket

6. 14 PIN JTAG CONNECTOR (P5) CONNECTOR USED


: 14 Pin Double row male connector

[ 25 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A MATING CONNECTOR

: 14 Pin Double row female Socket

7. ADC INPUT FRC CONNECTOR (P6) CONNECTOR USED 26 Pin Double Row Header (13*2)

Table – 4: Signal Description of P6 Connector MATING CONNECTOR 26 Pin Double row socket 8. J801 3 PIN CONNECTOR (P7) PIN CONFIGURATION 1 - GND 2 - DAC1 OUTPUT 3 - DAC2 OUTPUT


[ 26 ]


9. PWM OUTPUT 34 Pin FRC connector (P8) Connector Used

: 34 Pin Double Row Headers

SIGNAL DESCRIPTION

Table – 5: Signal Description of P8 Connector MATING CONNECTOR 34 Pin Double Row Socket


[ 27 ]


10. IBM PC KEYBOARD CONNECTOR: (P9) CONNECTOR USED 6 Pin PS2 Female Connector

Table – 6: Signal Description of P9 Connector SIGNAL DEFINITION CLK - Keyboard Clock DATA - Serial Data from keyboard MATING CONNECTOR 6 Pin PS2 Male Connector (Available in the IBM PC Keyboard itself)


[ 28 ]


8. VPET-106A 8.1 Front Panel View


[ 29 ]


Figure15: Front Panel View 8.2 Front Panel Description


[ 30 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A Power ON/OFF switch

-

To switch ON/OFF power to the module.

MCB

-

To control input AC voltage to the power circuit.

PWM INPUT

-

To connect the PWM input / feedback signal from / to the controller unit

R, Y, B

-

To connect 3· output to the load.

Voltmeter

-

To display DC link voltage.

P, N

-

To connect AC input to the module.

A+, A-, F+, (+)

-

To connect the DC output to the load.

RST

-

To reset the module.

PWM1, PWM 2...PWM 6

-

Test points to view the PWM signal to the switches with respect to ground point.

Idc, Ir, Iy, Ib

-

Test points to view the sensed input DC current & output R, Y and B phase currents.

PWM Isolation

-

To isolate the gate signals.

8.3 Hardware Description


[ 31 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A 8.3.1 Block Diagram

Figure 16 Block diagram for IGBT power module The block diagram for IGBT power module consists of the following. 1. Rectifier & Filter 2. Power circuit 3. Controller 4. Optoisolator 5. Gate Driver 6. Current Sensor 7. Signal conditioner 8. Protection Circuit.

8.3.2 Block Diagram Description


[ 32 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A 1. Rectifier & Filter The input AC voltage is rectified by the Diode Bridge Rectifier circuit. The rectified DC voltage is fed to the power circuit through a filter capacitor. The filter capacitor eliminates the unwanted ripple in the Dc input. 2. Power Circuit The Power circuit consists of three leg IGBT circuit. IGBT switch is used as a switching device in the power circuit. The PWM signal from the driver IC is fed to the gate of the switch. The output from the power circuit is given to the load. The output may be either AC/DC depending on the inverter/chopper mode of operation. 3. Controller The PWM signal to the IGBT switches is generated by the controller unit. The controller may be any processor. The PWM signal from the controller is fed to the module through the connector provided on the front panel. In this implementation, controller is used PWM generation. 4. Optoisolator (6N137) The function of Optoisolator is to isolate the control circuit from power circuit. PWM signal from the controller is not directly fed to the power circuit in order to protect the PWM signal it is essential to provide isolation circuit between power circuit and control circuit or else the high power components may damage the low power PWM circuit components. 5. Gate Driver (IR2110) An IGBT drive circuit is designed to connect the gate directly to a voltage bus with no intervening resistance other than the impedance of the drive circuit switch. Gate driver acts as a high-power buffer stage between the PWM output of the control device and gates of the primary power switching IGBT.

6. Current Sensor


[ 33 ]

Speed Control of AC Induction Motor using Micro – 2407 & VPET-106A IGBT power module output current is not directly fed to control (Protection) circuits. The sensor used for sensing current works on the principle of Hall Effect. Hence these sensors are called Hall Effect transducer. Hall Effect transducer output current depends upon transducer primary and secondary winding ratio. The turn’s ratio represents the ratio of the number of primary turns to the number of secondary turns. A Hall effect current transducer senses the current IDC, Ir(R), Iy(Y) Ib(B).

Figure 17: Current Transducer 7. Signal Conditioner The signal from the current sensor is fed back to the controller unit. The gain of the current signals has to be improved to achieve controller requirements. So the signal needs to be conditioned in the signal conditioner circuits.


[ 34 ]


Figure 18: Signal Conditioner 8. Protection Circuit In the protection circuit the DC current Idc is sensed. If the I dc value increases than the limit, the protection circuit activates and cuts the PWM to the switches in the module. The LED glows to indicate the system shut down condition. The system can be reset by the RST press button provided on the front panel. Now the LED switches OFF. Again the PWM signal should be applied to the system. Note: The sensing and conditioning of the output current is an optional future of this module and it is of additional cost to the module.


[ 35 ]


9. WIRING DIAGRAM

Figure 19: Wiring Diagram


[ 36 ]


10. EXPERIMENT 1. Open Loop Speed Control of 3? ACIM with Spring Balance Load setup using VF control (Sine PWM) using VPET-106A module & Micro-2407 trainer kit. Aim To study the Speed control of 3? ACIM with spring balance Load using VF Control (Sine PWM) using VPET-106A Module and Micro-2407 trainer kit. Equipments Required 1. VPET-106A Module 2. 3 ? AC induction motor 3. Micro-2407 Trainer 4. PC-PC serial port cable. 5. Patch Chords 6. 26 Pin FRC cable 7. 34 Pin FRC cable (dual type) 8. DC Regulated Power Supply (0-30V) Connection Procedure 1. Connect the 3? AC supply terminals to the “3? 440V AC input” terminals of the VPET-106A Module through the 3? -VARIAC. 2. Connect the VPET-106A module output terminals U, V and W to the input terminals of 3? AC induction motor.

3. Connect Micro-2407 trainer module to power supply. 4. Connect the 34 pin FRC cable one end to the 34 Pin FRC header in Micro - 2407 Trainer, one end to QEP signal conditioning card and the other end to “IGBTPWM INPUTS” in the VPET-106A Power Module.

5. Connect the speed feedback signal from the motor to QEP signal conditioning card through 9-pin ‘D’type 1:1 cable. 6. Connect FEEDBACK SIGNALS connector of VPET-106A and ADC connector of Micro-2407 trainer using 26 core FRC.

7. Connect Serial Port connector of PC to the 9-pin serial connector of Micro-2407 trainer using PC-PC serial port cable.


[ 37 ]


Experiment Procedure 1. Verify the connections as per the connection procedure and wiring diagram. 2. Switch ON the Micro-2407 Trainer. 3. Keep the auto transformer in minimum position, and then switch ON the power ON/OFF switch in the VPET-106A. Check whether shut down LED “SD” glows or not. If ‘SD’LED glows press the Reset switch, the LED gets OFF. 4. Switch ON the MCB, then slowly increase the 3? AC input to the module through the auto transformer and set the DC link voltage at 600V. 5. Switch ON the PC and then press Reset Switch of the Micro-2407 Trainer. 6. To download and execute the program, follow the “Program Download Procedure” given below.

Program Download Procedure for Micro-2407 Based AC Induction Motor Control Applications Using C2407 Debugger


[ 38 ]


AC MOTOR OPEN LOOP DOWNLOADING PROCEDURE

1. Double Click C2407 icon from the target directory or from the desktop. Now the window shows.


[ 39 ]


2. Now configure the serial port settings and press ‘OK’button. Now the window shows.


[ 40 ]


2. Select the required program to be downloaded. For open loop AC motor with Sine/Tri or space vector Modulation select Open Loop — > AC Motor — > Sine/Tri or Space vector.


[ 41 ]


3. This window appears.


[ 42 ]


4. Ensure whether the motor is connected or not. Then click ‘OK’.


[ 43 ]


6. Click ‘Send’then the window shows below..


[ 44 ]


7. Click ‘OK’(the particular file will be download to controller) then the window shows


[ 45 ]


8. Now the transmission completed message appears, click ‘OK’and then click ‘EXECUTE’ 9. Check the all PWMs by connecting CRO. Now apply AC voltage though single phase variac upto 300VDC. 10. Now, the speed value is plotted then speed and frequency numerical values are displayed. 11. To change the speed of the motor, use the increment/decrement switch in the 2407 kit.

12. To measure i/p voltage of the motor, connect Ac voltmeter (0- 450 V) across U and V terminals of the VPET-106A and frequency is obtained from the front end software. Now check the V/F ratio of the motor. 13. By applying load to the motor, motor speed is not remains constant and it is not equal to the set speed. 14. To measure the load current of the motor, externally connect one AC ammeter in series with any one phase. (Ref: connection diagram)


[ 46 ]


2. Close Loop Speed Control of 3? ACIM with Spring Balance Load setup using VF control (Sine PWM) using VPET-106A module & Micro-2407 trainer kit. Aim To study the Speed control of 3? ACIM with spring balance Load using VF Control (Sine PWM) using VPET-106A Module and Micro-2407 trainer kit. Equipments Required 1. VPET-106A Module 2. 3 ? AC induction motor 3. Micro-2407 Trainer 4. PC-PC serial port cable. 5. Patch Chords 6. 26 Pin FRC cable 7. 34 Pin FRC cable (dual type) 8. DC Regulated Power Supply (0-30V) Connection Procedure 1. Connect the 3? AC supply terminals to the “3? 440V AC input” terminals of the VPET-106A Module through the 3? -VARIAC. 2. Connect the VPET-106A module output terminals U, V and W to the input terminals of 3? AC induction motor. 3. Connect Micro-2407 trainer module to power supply. 4. Connect the 34 pin FRC cable one end to the 34 Pin FRC header in Micro - 2407 Trainer, one end to QEP signal conditioning card and the other end to “IGBT- PWM INPUTS” in the VPET-106A Power Module. 5. Connect the speed feedback signal from the motor to QEP signal conditioning card through 9-pin ‘D’type 1:1 cable. 6. Connect FEEDBACK SIGNALS connector of VPET-106A and ADC connector of Micro-2407 trainer using 26 core FRC. 7. Connect Serial Port connector of PC to the 9-pin serial connector of Micro-2407 trainer using PC-PC serial port cable.


[ 47 ]


Experiment Procedure 1. Verify the connections as per the connection procedure and wiring diagram. 2. Switch ON the Micro-2407 Trainer. 3. Keep the auto transformer in minimum position, and then switch ON the power ON/OFF switch in the VPET-106A. Check whether shut down LED “SD” glows or not. If ‘SD’LED glows press the Reset switch, the LED gets OFF. 4. Switch ON the MCB, then slowly increase the 3? AC input to the module through the auto transformer and set the DC link voltage at 600V. 5. Switch ON the PC and then press Reset Switch of the Micro-2407 Trainer. 6. To download and execute the program, follow the “Program Download Procedure” given below.

PROGRAM DOWNLOAD PROCEDURE FOR MICRO-2407 BASED AC INDUCTION MOTOR CONTROL APPLICATIONS USING C2407 DEBUGGER


[ 48 ]


AC MOTOR CLOSED LOOP DOWLOADING PROCEDURE

1.Double Click C2407 icon from the target directory or from the desktop. Now the window shows.


[ 49 ]


2. Now configure the serial port settings and press ‘OK’button. Now the window shows.


[ 50 ]


2.Select the required program to be downloaded. For close loop AC motor with Sine/Tri or space vector Modulation select Close Loop — > AC Motor — > Sine/Tri or Space vector.


[ 51 ]


5. This window appears.


[ 52 ]


6. Ensure whether the motor is connected or not. Then click ‘OK’.


[ 53 ]


7. Click ‘Send’then the window shows below..


[ 54 ]


8. Click ‘OK’(the particular file will be download to controller) then the window shows


[ 55 ]


9. Now the transmission completed message appears, click ‘OK’and then click ‘EXECUTE’ 10. Check the all PWMs by connecting CRO. Now apply AC voltage though single phase variac upto 300VDC. 11. Now, the speed value is plotted then speed and frequency numerical values are displayed. 12. To change the speed of the motor, use the increment/decrement switch in the 2407 kit. 13. To measure i/p voltage of the motor, connect Ac voltmeter (0- 450 V) across U and V terminals of the VPET-106A and frequency is obtained from the front end software. Now check the V/F ratio of the motor.

14. By applying load to the motor, motor speed is remains constant and it is equal to the set speed. 15. To measure the load current of the motor, externally connect one AC ammeter in series with any one phase. (Ref: connection diagram)


[ 56 ]

Speed Control of 3 Phase Ac Induction Motor Using Micro 2407

Recommend Documents