MICADURâ-Compact Industry (MCI) Insulation System based on Vacuum-Pressure Impregnation (VPI) and has been used 20 years and it is well known for its high reliability.
Winding insulation exceeds Class F requirements (temperature limit 155°C).
The complete winding and its supporting structures are vacuum pressure impregnated with epoxy resin which ensures a very robust, solid and moisture resistant insulation.
Insulation voltage level is matched to converter voltage waveform
VPI is used for all stators and rotors
Terminals
The stator line terminals and neutral terminals are situated in the top box on the top of the generator
Excitation transformers are installed in the terminal box
The terminals for excitation and control equipment are in auxiliary terminal box Main Terminals
Type test performed on one of a series of identical motors
Special tests performed as required
Routine tests 1. Visual inspection 2. Air gap measurement and clearance check of sleeve bearings 3. Insulation resistance measurement in cold condition 4. Winding resistance measurement 5. Checking of temperature detectors and space heaters 6. Terminal markings and direction of rotation 7. Axial play for unlocked bearing 8. Bearing run 9. Vibration measurement 10. No load point 11. Short circuit point 12. High voltage tests 13. Overspeed test for generator 14. Tests of excitation cubicle 15. Insulation resistance measurement in hot condition
Type tests 16. Moment of inertia 17. No load curve 18. Short circuit curve 19. Heat run test (temperature rise test) / IEC 34-1 + IEEE 115 20. Zero power factor test 22. Losses and efficiency
Special tests 1. Sound level measurement at no load / ISO 3744 2. Sudden short circuit test / IEC 34-4 + IEEE 115 3. Measurement of the shaft voltage 4. Wave form measurement / IEC 34-1 + IEEE 115 5. Load switching on / off test 6. Starting of the synchronous motor (locked rotor test) 7. Polarization index / IEEE 43
Recommended spares for AMG/AMZ machine
1. Safety Parts
2. Maintenance Parts
Protection units Water cooler element Cooling air motor & fan Slip rings Voltage and current transformers Space heater
Excitation system Rectifier bridge semiconductors Temperature sensors Bearing parts Oil lubrication unit Brushes and brush holders Tachometers and encoders
Exciter rotor and stator Rectifier bridge Rotor pole Rotor complete Stator (wound core) Stator with frame
. B 1 B . A d r e a v e r y e t s h e r 4 g s 0 i r t 0 y h 2 p i g / o r 1 C 0
Cycloconverter Low speed and high power frequency converter
2 e c i v r e s t c 3 u d 0 0 o r 2 P
Runs always synchronous motor (AC motor with DC excitation)
Power up to 27MW
Motor nominal voltage 1350V... 1570V
Maximum continuous current up to 4500A(water cooled)
Nominal speed of delivered motors 30…220rpm
Maximum speed 720rpm
Cycloconverter in metals Rolling mills
3 e c i v r e s t c 3 u d 0 0 o r 2 P
Nominal power
0,5...15 MW
Max. load
115...300 %
High torques
>1000 kNm
Roughing mills for steel and aluminium
Z-mills for stainless steel
Tandem Cold rolling mills
Cold mills for aluminium and copper
Performance and availability are most important
Cycloconverter in Marine with Azipod Main propeller
4 e c i v r e s t c 3 u d 0 0 o r 2 P
Nominal power
up to 20 MW
Speed
100..300rpm
In cruise vessel normally 2 or 3 main propellers
Safety and redundancy are really important
Operation of synchronous motor
N
S
5 e c i v r e s t c 3 u d 0 0 o r 2 P
The magnetic field of the stator attracts the rotor magnet
The rotor rotates until the rotor N-pole meets the S-pole of stator
Continuous rotation is not possible with permanent magnet
Operation of synchronous motor Stator magnetic field
N S
_ +
_ +
Battery voltage makes current
Current induce field
Battery voltage polarity reversing
Stator magnetic polarity swap
Rotor turns 180°
Right timing of U swaps
Continuous rotor rotation is possible thought starting may be difficult from certain positions
Jumpy torque
N S
6 e c i v r e s t c 3 u d 0 0 o r 2 P
Attracts rotor magnet
Operation of synchronous motor Stator
In order to allow starting in any position a stator with 3 phase winding is used A phase winding is divided in two parts opposite side of stator
Excitation
7 e c i v r e s t c 3 u d 0 0 o r 2 P
Rotor permanent magnet is also replaced with winding
Operation of synchronous motor DC pulse control(simple method)
Torque is not smooth
Step operation(stepper motor)
AC sinusoidal supply
8 e c i v r e s t c 3 u d 0 0 o r 2 P
Smooth torque
If frequency and voltage can be controlled also motor speed can be controlled
SM frequency vs. speed
9 e c i v r e s t c 3 u d 0 0 o r 2 P
Motor power supply Main requirements for the power supply of motor
0 1 e c i v r e s t c 3 u d 0 0 o r 2 P
Sinusoidal phase currents
Variable frequency and voltage
Low losses (cyclo efficiency is >99,5 % at rated load)
Can be easily connected to utility’s power network
Fast control of currents for fast torque control
Cycloconverter CONSTANT FREQUENCY AC NETWORK 50 / 60 HZ
3 -PHASE
VARIABLE FREQUENCY 0...20 / 24 HZ
M
1 1 e c i v r e s t c 3 u d 0 0 o r 2 P
Input frequency 50 or 60 Hz + 5 %
Input voltage 1000V(1000V or 1200V in marine)
Output voltage controllable 0…1500V(0…1570 in marine)
Output frequency controllable 0...20 / 24 Hz
Auxiliary voltage 220..690VAC
Supply network Three phase constant frequency (50 Hz or 60 Hz) constant voltage system u
r time
u
s
u
t
20 ms (for 50 Hz) 16.7 ms (for 60 Hz)
2 1 e c i v r e s t c 3 u d 0 0 o r 2 P
1 second = 1000 milliseconds = 1000 ms
SCR thyristor Semiconductor switch
Switches in the rectifiers have to be fast, in 50 Hz network they have to close and open 50 times every second Thus mechanical switches are unsuitable and a semiconductor switch is used instead A high power thyristor is a 0.5 mm thick and 50 - 150 mm diameter disk of silicon packed in a housing made of metal and ceramics A thyristor can withstand a voltage of over 5000 volts and conduct a current of several thousand amperes(4200 or 5200 Volts SCR’s used in cycloconverter) Thyristor is controlled by a short gate current pulse of few amperes (the firing pulse) Anode
3 1 e c i v r e s t c 3 u d 0 0 o r 2 P
Cathode
A
K G Gate
Controlled bridge α=0
u
α≠0
U output
r time
4 1 e c i v r e s t c 3 u d 0 0 o r 2 P
u
s
u
t
u
+
Average voltage
Output voltage can be controller by controlling firing angle
Motor current can be controlled by controlling drive output voltage
Firing angle
5 1 e c i v r e s t c 3 u d 0 0 o r 2 P
Sinusoidal output Supply voltage
U output
I output
6 1 e c i v r e s t c 3 u d 0 0 o r 2 P
Positive and negative thyristor bridge 1
Thyristor bridge change time
0,5
0
I 0
-0,5
-1
7 1 e c i v r e s t c 3 u d 0 0 o r 2 P
90
180
270
360
Phase currents Phase currents of a rolling mill cycloconverter drive, f = 8 Hz (simulation)
1.5
Phase b current
Phase a current
Phase c current
1
0.5
t i n u r e p
0 600
620
640
660
680
700
720
740
760
780
Time (ms) -0.5
-1 8 1 e c i v r e s t c 3 u d 0 0 o r 2 P
-1.5
800
Phase voltages Phase voltages of a rolling mill cycloconverter drive, f = 8 Hz (simulation)
1.5
Phase a voltage
Phase b voltage
Phase c voltage
1
0.5
t i n u r e p
0 600
620
640
660
680
700
720
740
760
780
Time (ms) -0.5
-1 9 1 e c i v r e s t c 3 u d 0 0 o r 2 P
-1.5
800
Cycloconverter drive Phase current
0 2 e c i v r e s t c 3 u d 0 0 o r 2 P
Excitation current (DC current)
Positive bridge
Negative bridge
Operation curves, VOLTAGE and FLUX All electrical motors have a so called base speed or nominal speed. On AC motors it is related to frequency. Constant flux/torque range
Nominal flux
Field weakening/ constant power range
Flux
Nominal voltage
• at this speed the motor voltage is nominal(100%) • below this speed excitation current is kept constant • if speed is increased above this speed motor flux has to be reduced to prevent motor over voltage . Stator voltage formula is Us = * Ψ = flux, controlled by excitation current ω = speed
Voltage
This means that faster the motor is running the higher is the voltage provided that flux is kept constant At zero speed flux is nominal 100% and speed 0%, thus Us=100% * 0% = 0%
0 1 2 e c i v r e s t c 3 u d 0 0 o r 2 P
Base speed
Speed
At nominal speed both flux and speed are nominal, then Us=100% * 100% =100%=Nominal voltage If speed is increased over the base speed then flux(i.e.. excitation current) has to be reduced. For example 2 * base speed. Us= * = 50% * 200% = 100%
Operation curves, TORQUE Constant flux/torque range
Field weakening/ constant power range
Motor torque is the product of flux and torque. Motor torque formula is T =
* Is
Torque
= flux, controlled by excitation current Is = stator current
Flux
Normally all drives can produce full current through the whole speed range. Same applies also to cycloconverter.
Stator current
Because flux is reduced in field weakening area the absolute torque(Nm) is reduced.
Ψ
0 2 2 e c i v r e s t c 3 u d 0 0 o r 2 P
Base speed
Speed
Operation curves, POWER Constant flux/torque range
Field weakening/ constant power range
Motor shaft power is product of torque and speed. Motor power formula is P = T * T = Torque ω = motor speed
Torque
Flux
This means that full power could be reached only at base speed.
Power Power
Speed
0 3 2 e c i v r e s t c 3 u d 0 0 o r 2 P
Base speed
Speed
Operation curves, propeller and fan Constant flux/torque range
Field weakening constant power range
Load curve of propeller or fan is quadratic. Motor torque
For example in cruise liner main propulsion field weakening point could be 125rpm and maximum speed Maximum power 145rpm.
