eemf troubleshooting on electrical machines
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Lucas-Nülle Lehr- und Messgeräte GmbH Siemensstraße 2 • D-50170 Kerpen
Troubleshooting on
electrical machines
EEM/F
Student workbook
SH5002-3P
2nd edition
Author: Ralf Linnertz
Troubleshooting on electrical machines
EEM/F TABLE OF CONTENTS
Table of contents
Equipment.............................................................................................................................................. 1
Basic experiment without fault simulator .......................................................................................... 3
Fault switch 2 actuated ........................................................................................................................ 9
Fault switch 5 actuated ...................................................................................................................... 15
Fault switch 11 actuated.................................................................................................................... 21
Fault switches 1 and 4 actuated....................................................................................................... 27
Fault switches 3 and 6 actuated....................................................................................................... 33
Fault switches 4 and 5 actuated....................................................................................................... 39
Fault switches 5 and 8 actuated....................................................................................................... 45
All fault switches actuated................................................................................................................. 51
Troubleshooting on electrical machines
EEM/F TABLE OF CONTENTS
Troubleshooting on electrical machines
EEM/F EQUIPMENT 1
Equipment
Device Quantity
SE2662-9D Fault simulator 1
LM8501 Metriso C insulation tester 1
SE2662-3G, SE2672-3G SE2663-1k, SE2673-1k SE2662-5G, SE2672-5G SE2663-1H, SE2673-1H
Three-phase motor with squirrel-cage rotor, 0.3 kW/1 kW
1
Troubleshooting on electrical machines
2 EEM/F EQUIPMENT
Troubleshooting on electrical machines
EEM/F/1 BASIC EXPERIMENT WITHOUT FAULT SIMULATION 3
Basic experiment without fault simulation
Experiment objectives
Exercises:
• Measurement of winding resistance in a three-phase induction motor with squirrel-cage rotor
• Measurement of insulation resistance in a three-phase induction motor with squirrel-cage rotor
• Identification of winding and/or insulation faults
Troubleshooting on electrical machines
4 EEM/F/1 BASIC EXPERIMENT WITHOUT FAULT SIMULATION
Circuit
U1 V1 W1
W2 U2 V2
M
3~
Sample measurements
U1 V1 W1
W2 U2 V2
Ω
ΩΩ
Terminal panel
Screen terminal
Housing (frame)
Stator coil W
Stator coil V
Stator coil U
Winding-to-winding insulation resistance measurement
Winding-to-housing insulation resistance measurement
Winding resistance measurement
Troubleshooting on electrical machines
EEM/F/1 BASIC EXPERIMENT WITHOUT FAULT SIMULATION 5
Equipment/components
• Three-phase induction motor with squirrel-cage rotor
• Multimeter (or ohmmeter, if available)
• Insulation tester Note: The winding resistances (coil U, coil V, coil W) of a three-phase induction motor must be identical in order to generate a symmetrical rotating field in the stator. However, even if the winding resistances are identical, it is still possible for insulation faults to occur (winding-to-winding or winding-to-frame). A winding-to-winding insulation fault can result in a short circuit (triggering the circuit breaker) or overcurrent which is then shut off by the motor protection relay or a general motor protection mechanism (NTC, PTC). A winding-to-frame insulation fault can pose a contact hazard since a potential difference arises between the housing or frame and earth. In this case, it is important to install a dependable protective mechanism which disconnects the motor from the mains when hazardous contact voltages (> 50 V) occur. The measured winding resistances should be approximately equal to the following values:
270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).
The insulation resistances must be at least 1 kΩ/V according to VDE specifications. This means that no insulation fault should be present as long as the winding-to-winding resistance
is at least 400kΩ and the resistance between windings and the grounded frame or housing
is at least 230kΩ.
Troubleshooting on electrical machines
6 EEM/F/1 BASIC EXPERIMENT WITHOUT FAULT SIMULATION
Measurement procedure
Select a suitable measuring instrument, measure the winding resistance for each of the coils U, V, W and enter the values in the table provided. Winding resistance can be measured with a universal multimeter (or an ohmmeter).
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
Coil U (U1-U2)
Coil V (V1-V2)
Coil W (W1-W2)
Select a suitable measuring instrument, measure the winding-to-winding insulation resistance values and enter the values in the table provided. Winding-to-winding insulation resistance can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 – V1
U1 – W1
V1 – W1
U2 – V2
U2 – W2
V2- W2
Troubleshooting on electrical machines
EEM/F/1 BASIC EXPERIMENT WITHOUT FAULT SIMULATION 7
Select a suitable measuring instrument, measure the insulation resistance values between
windings and the frame or housing and enter the values in the table provided for this purpose.
The resistance between windings and frame can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 –
V1 –
W1 –
U2 –
V2 –
W2-
Troubleshooting on electrical machines
8 EEM/F/1 BASIC EXPERIMENT WITHOUT FAULT SIMULATION
Fill in all the measurements on the following diagram of the motor.
What can be said about the motor windings and insulation?
Troubleshooting on electrical machines
EEM/F/2 FAULT SWITCH 2 ACTUATED 9
Fault switch 2 actuated
Experiment objectives
Exercises:
• Measurement of winding resistance in a three-phase induction motor with squirrel-cage rotor
• Measurement of insulation resistance in a three-phase induction motor with squirrel-cage rotor
• Identification of winding and/or insulation faults
Open the fault simulator and actuate fault switch 2 without simulating any other faults. Close the fault simulator again.
Troubleshooting on electrical machines
10 EEM/F/2 FAULT SWITCH 2 ACTUATED
Circuit
U1 V1 W1
W2 U2 V2
M
3~
Sample measurements
U1 V1 W1
W2 U2 V2
Ω
ΩΩ
Terminal panel
Screen terminal
Housing (frame)
Stator coil "W"
Stator coil "V"
Stator coil "U"
Winding-to-winding insulation resistance measurement
Winding-to-frame insulation resistance measurement
Winding resistance
Troubleshooting on electrical machines
EEM/F/2 FAULT SWITCH 2 ACTUATED 11
Equipment/components
• Three-phase induction motor with squirrel-cage rotor
• Multimeter (or ohmmeter, if available)
• Insulation tester
Note: The winding resistances (coil U, coil V, coil W) of a three-phase induction motor must be identical in order to generate a symmetrical rotating field in the stator. However, even if the winding resistances are identical, it is still possible for insulation faults to occur (winding-to-winding or winding-to-frame). A winding-to-winding insulation fault can result in a short circuit (triggering the circuit breaker) or overcurrent which is then shut off by the motor protection relay or a general motor protection mechanism (NTC, PTC). A winding-to-frame insulation fault can pose a contact hazard since a potential difference arises between the housing or frame and earth. In this case, it is important to install a dependable protective mechanism which disconnects the motor from the mains when hazardous contact voltages (> 50 V) occur. The measured winding resistances should be approximately equal to the following values:
270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).
The insulation resistances must be at least 1 kΩ/V according to VDE specifications. This means that no insulation fault should be present as long as the winding-to-winding resistance
is at least 400kΩ and the resistance between windings and the grounded frame or housing
is at least 230kΩ.
Troubleshooting on electrical machines
12 EEM/F/2 FAULT SWITCH 2 ACTUATED
Measurement procedure
Select a suitable measuring instrument, measure the winding resistance for each of the coils U, V, W and enter the values in the table provided. Winding resistance can be measured with a ___________________________________________________..
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
Coil U (U1-U2)
Coil V (V1-V2)
Coil W (W1-W2)
Select a suitable measuring instrument, measure the winding-to-winding insulation resistance values and enter the values in the table provided. Winding-to-winding insulation resistance can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 – V1
U1 – W1
V1 – W1
U2 – V2
U2 – W2
V2- W2
Troubleshooting on electrical machines
EEM/F/2 FAULT SWITCH 2 ACTUATED 13
Select a suitable measuring instrument, measure the insulation resistance values between
windings and the frame or housing and enter the values in the table provided for this purpose.
The resistance between windings and frame can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 –
V1 –
W1 –
U2 –
V2 –
W2-
Troubleshooting on electrical machines
14 EEM/F/2 FAULT SWITCH 2 ACTUATED
Fill in all the measurements on the following diagram of the motor.
What can be said about the motor windings and insulation?
Troubleshooting on electrical machines
EEM/F/3 FAULT SWITCH 5 ACTUATED 15
Fault switch 5 actuated
Experiment objectives
Exercises:
• Measurement of winding resistance in a three-phase induction motor with squirrel-cage rotor
• Measurement of insulation resistance in a three-phase induction motor with squirrel-cage rotor
• Identification of winding and/or insulation faults
Open the fault simulator and actuate fault switch 5 without simulating any other faults. Close the fault simulator again.
Troubleshooting on electrical machines
16 EEM/F/3 FAULT SWITCH 5 ACTUATED
Circuit
U1 V1 W1
W2 U2 V2
M
3~
Sample measurements
U1 V1 W1
W2 U2 V2
Ω
ΩΩ
Terminal panel
Screen terminal
Housing (frame)
Stator coil "W"
Stator coil "V"
Stator coil "U"
Winding-to-winding insulation resistance measurement
Winding-to-frame insulation resistance measurement
Winding resistance measurement
Troubleshooting on electrical machines
EEM/F/3 FAULT SWITCH 5 ACTUATED 17
Equipment/components
• Three-phase induction motor with squirrel-cage rotor
• Multimeter (or ohmmeter, if available)
• Insulation tester Note: The winding resistances (coil U, coil V, coil W) of a three-phase induction motor must be identical in order to generate a symmetrical rotating field in the stator. However, even if the winding resistances are identical, it is still possible for insulation faults to occur (winding-to-winding or winding-to-frame). A winding-to-winding insulation fault can result in a short circuit (triggering the circuit breaker) or overcurrent which is then shut off by the motor protection relay or a general motor protection mechanism (NTC, PTC). A winding-to-frame insulation fault can pose a contact hazard since a potential difference arises between the housing or frame and earth. In this case, it is important to install a dependable protective mechanism which disconnects the motor from the mains when hazardous contact voltages (> 50 V) occur. The measured winding resistances should be approximately equal to the following values:
270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).
The insulation resistances must be at least 1 kΩ/V according to VDE specifications. This means that no insulation fault should be present as long as the winding-to-winding resistance
is at least 400kΩ and the resistance between windings and the grounded frame or housing
is at least 230kΩ.
Troubleshooting on electrical machines
18 EEM/F/3 FAULT SWITCH 5 ACTUATED
Measurement procedure
Select a suitable measuring instrument, measure the winding resistance for each of the coils U, V, W and enter the values in the table provided. Winding resistance can be measured with a ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
Coil U (U1-U2)
Coil V (V1-V2)
Coil W (W1-W2)
Select a suitable measuring instrument, measure the winding-to-winding insulation resistance values and enter the values in the table provided. Winding-to-winding insulation resistance can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 – V1
U1 – W1
V1 – W1
U2 – V2
U2 – W2
V2- W2
Troubleshooting on electrical machines
EEM/F/3 FAULT SWITCH 5 ACTUATED 19
Select a suitable measuring instrument, measure the insulation resistance values between windings and the frame or housing and enter the values in the table provided for this purpose.
The resistance between windings and frame can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 –
V1 –
W1 –
U2 –
V2 –
W2-
Troubleshooting on electrical machines
20 EEM/F/3 FAULT SWITCH 5 ACTUATED
Fill in all the measurements on the following diagram of the motor.
What can be said about the motor windings and insulation?
Troubleshooting on electrical machines
EEM/F/4 FAULT SWITCH 11 ACTUATED 21
Fault switch 11 actuated
Experiment objectives
Exercises:
• Measurement of winding resistance in a three-phase induction motor with squirrel-cage rotor
• Measurement of insulation resistance in a three-phase induction motor with squirrel-cage rotor
• Identification of winding and/or insulation faults
Open the fault simulator and actuate fault switch 11 without simulating any other faults.
Close the fault simulator again.
Troubleshooting on electrical machines
22 EEM/F/4 FAULT SWITCH 11 ACTUATED
Circuit
U1 V1 W1
W2 U2 V2
M
3~
Sample measurements
U1 V1 W1
W2 U2 V2
Ω
ΩΩ
Terminal panel
Screen terminal
Housing (frame)
Stator coil "W"
Stator coil "V"
Stator coil "U"
Winding-to-winding insulation resistance measurement
Winding-to-frame insulation resistance measurement
Winding resistance measurement
Troubleshooting on electrical machines
EEM/F/4 FAULT SWITCH 11 ACTUATED 23
Equipment/components
• Three-phase induction motor with squirrel-cage rotor
• Multimeter (or ohmmeter, if available)
• Insulation tester Note: The winding resistances (coil U, coil V, coil W) of a three-phase induction motor must be identical in order to generate a symmetrical rotating field in the stator. However, even if the winding resistances are identical, it is still possible for insulation faults to occur (winding-to-winding or winding-to-frame). A winding-to-winding insulation fault can result in a short circuit (triggering the circuit breaker) or overcurrent which is then shut off by the motor protection relay or a general motor protection mechanism (NTC, PTC). A winding-to-frame insulation fault can pose a contact hazard since a potential difference arises between the housing or frame and earth. In this case, it is important to install a dependable protective mechanism which disconnects the motor from the mains when hazardous contact voltages (> 50 V) occur. The measured winding resistances should be approximately equal to the following values:
270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).
The insulation resistances must be at least 1 kΩ/V according to VDE specifications. This means that no insulation fault should be present as long as the winding-to-winding resistance
is at least 400kΩ and the resistance between windings and the grounded frame or housing
is at least 230kΩ.
Troubleshooting on electrical machines
24 EEM/F/4 FAULT SWITCH 11 ACTUATED
Measurement procedure
Select a suitable measuring instrument, measure the winding resistance for each of the coils U, V, W and enter the values in the table provided. Winding resistance can be measured with a ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
Coil U (U1-U2)
Coil V (V1-V2)
Coil W (W1-W2)
Select a suitable measuring instrument, measure the winding-to-winding insulation resistance values and enter the values in the table provided. Winding-to-winding insulation resistance can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 – V1
U1 – W1
V1 – W1
U2 – V2
U2 – W2
V2- W2
Troubleshooting on electrical machines
EEM/F/4 FAULT SWITCH 11 ACTUATED 25
Select a suitable measuring instrument, measure the insulation resistance values between
windings and the frame or housing and enter the values in the table provided for this purpose.
The resistance between windings and frame can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 –
V1 –
W1 –
U2 –
V2 –
W2-
Troubleshooting on electrical machines
26 EEM/F/4 FAULT SWITCH 11 ACTUATED
Fill in all the measurements on the following diagram of the motor.
What can be said about the motor windings and insulation?
Troubleshooting on electrical machines
EEM/F/5 FAULT SWITCHES 1 AND 4 ACTUATED 27
Fault switches 1 and 4 actuated
Experiment objectives
Exercises:
• Measurement of winding resistance in a three-phase induction motor with squirrel-cage rotor
• Measurement of insulation resistance in a three-phase induction motor with squirrel-cage rotor
• Identification of winding and/or insulation faults
Open the fault simulator and actuate fault switches 1 and 4 without simulating any other faults. Close the fault simulator again.
Troubleshooting on electrical machines
28 EEM/F/5 FAULT SWITCHES 1 AND 4 ACTUATED
Circuit
U1 V1 W1
W2 U2 V2
M
3~
Sample measurements
U1 V1 W1
W2 U2 V2
Ω
ΩΩ
Terminal panel
Screen terminal
Housing (frame)
Stator coil "W"
Stator coil "V"
Stator coil "U"
Winding-to-winding insulation resistance measurement
Winding-to-frame insulation resistance measurement
Winding resistance measurement
Troubleshooting on electrical machines
EEM/F/5 FAULT SWITCHES 1 AND 4 ACTUATED 29
Equipment/components
• Three-phase induction motor with squirrel-cage rotor
• Multimeter (or ohmmeter, if available)
• Insulation tester Note: The winding resistances (coil U, coil V, coil W) of a three-phase induction motor must be identical in order to generate a symmetrical rotating field in the stator. However, even if the winding resistances are identical, it is still possible for insulation faults to occur (winding-to-winding or winding-to-frame). A winding-to-winding insulation fault can result in a short circuit (triggering the circuit breaker) or overcurrent which is then shut off by the motor protection relay or a general motor protection mechanism (NTC, PTC). A winding-to-frame insulation fault can pose a contact hazard since a potential difference arises between the housing or frame and earth. In this case, it is important to install a dependable protective mechanism which disconnects the motor from the mains when hazardous contact voltages (> 50 V) occur. The measured winding resistances should be approximately equal to the following values:
270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).
The insulation resistances must be at least 1 kΩ/V according to VDE specifications. This means that no insulation fault should be present as long as the winding-to-winding resistance
is at least 400kΩ and the resistance between windings and the grounded frame or housing
is at least 230kΩ.
Troubleshooting on electrical machines
30 EEM/F/5 FAULT SWITCHES 1 AND 4 ACTUATED
Measurement procedure
Select a suitable measuring instrument, measure the winding resistance for each of the coils U, V, W and enter the values in the table provided. Winding resistance can be measured with a ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
Coil U (U1-U2)
Coil V (V1-V2)
Coil W (W1-W2)
Select a suitable measuring instrument, measure the winding-to-winding insulation resistance values and enter the values in the table provided. Winding-to-winding insulation resistance can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 – V1
U1 – W1
V1 – W1
U2 – V2
U2 – W2
V2- W2
Troubleshooting on electrical machines
EEM/F/5 FAULT SWITCHES 1 AND 4 ACTUATED 31
Select a suitable measuring instrument, measure the insulation resistance values between
windings and the frame or housing and enter the values in the table provided for this purpose.
The resistance between windings and frame can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 –
V1 –
W1 –
U2 –
V2 –
W2-
Troubleshooting on electrical machines
32 EEM/F/5 FAULT SWITCHES 1 AND 4 ACTUATED
Fill in all the measurements on the following diagram of the motor.
What can be said about the motor windings and insulation?
Troubleshooting on electrical machines
EEM/F/6 FAULT SWITCHES 3 AND 6 ACTUATED 33
Fault switches 3 and 6 actuated
Experiment objectives
Exercises:
• Measurement of winding resistance in a three-phase induction motor with squirrel-cage rotor
• Measurement of insulation resistance in a three-phase induction motor with squirrel-cage rotor
• Identification of winding and/or insulation faults
Open the fault simulator and actuate fault switches 3 and 6 without simulating any other faults. Close the fault simulator again.
Troubleshooting on electrical machines
34 EEM/F/6 FAULT SWITCHES 3 AND 6 ACTUATED
Circuit
U1 V1 W1
W2 U2 V2
M
3~
Sample measurements
U1 V1 W1
W2 U2 V2
Ω
ΩΩ
Terminal panel
Screen terminal
Housing (frame)
Stator coil "W"
Stator coil "V"
Stator coil "U"
Winding-to-winding insulation resistance measurement
Winding-to-frame insulation resistance measurement
Winding resistance measurement
Troubleshooting on electrical machines
EEM/F/6 FAULT SWITCHES 3 AND 6 ACTUATED 35
Equipment/components
• Three-phase induction motor with squirrel-cage rotor
• Multimeter (or ohmmeter, if available)
• Insulation tester Note: The winding resistances (coil U, coil V, coil W) of a three-phase induction motor must be identical in order to generate a symmetrical rotating field in the stator. However, even if the winding resistances are identical, it is still possible for insulation faults to occur (winding-to-winding or winding-to-frame). A winding-to-winding insulation fault can result in a short circuit (triggering the circuit breaker) or overcurrent which is then shut off by the motor protection relay or a general motor protection mechanism (NTC, PTC). A winding-to-frame insulation fault can pose a contact hazard since a potential difference arises between the housing or frame and earth. In this case, it is important to install a dependable protective mechanism which disconnects the motor from the mains when hazardous contact voltages (> 50 V) occur. The measured winding resistances should be approximately equal to the following values:
270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).
The insulation resistances must be at least 1 kΩ/V according to VDE specifications. This means that no insulation fault should be present as long as the winding-to-winding resistance
is at least 400kΩ and the resistance between windings and the grounded frame or housing
is at least 230kΩ.
Troubleshooting on electrical machines
36 EEM/F/6 FAULT SWITCHES 3 AND 6 ACTUATED
Measurement procedure
Select a suitable measuring instrument, measure the winding resistance for each of the coils U, V, W and enter the values in the table provided. Winding resistance can be measured with a ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
Coil U (U1-U2)
Coil V (V1-V2)
Coil W (W1-W2)
Select a suitable measuring instrument, measure the winding-to-winding insulation resistance values and enter the values in the table provided. Winding-to-winding insulation resistance can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 – V1
U1 – W1
V1 – W1
U2 – V2
U2 – W2
V2- W2
Troubleshooting on electrical machines
EEM/F/6 FAULT SWITCHES 3 AND 6 ACTUATED 37
Select a suitable measuring instrument, measure the insulation resistance values between
windings and the frame or housing and enter the values in the table provided for this purpose.
The resistance between windings and frame can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 –
V1 –
W1 –
U2 –
V2 –
W2-
Troubleshooting on electrical machines
38 EEM/F/6 FAULT SWITCHES 3 AND 6 ACTUATED
Fill in all the measurements on the following diagram of the motor.
What can be said about the motor windings and insulation?
Troubleshooting on electrical machines
EEM/F/7 FAULT SWITCHES 4 AND 5 ACTUATED 39
Fault switches 4 and 5 actuated
Experiment objectives
Exercises:
• Measurement of winding resistance in a three-phase induction motor with squirrel-cage rotor
• Measurement of insulation resistance in a three-phase induction motor with squirrel-cage rotor
• Identification of winding and/or insulation faults
Open the fault simulator and actuate fault switches 4 and 5 without simulating any other faults. Close the fault simulator again.
Troubleshooting on electrical machines
40 EEM/F/7 FAULT SWITCHES 4 AND 5 ACTUATED
Circuit
U1 V1 W1
W2 U2 V2
M
3~
Sample measurements
U1 V1 W1
W2 U2 V2
Ω
ΩΩ
Terminal panel
Screen terminal
Housing (frame)
Stator coil "W"
Stator coil "V"
Stator coil "U"
Winding-to-winding insulation resistance measurement
Winding-to-frame insulation resistance measurement
Winding resistance measurement
Troubleshooting on electrical machines
EEM/F/7 FAULT SWITCHES 4 AND 5 ACTUATED 41
Equipment/components
• Three-phase induction motor with squirrel-cage rotor
• Multimeter (or ohmmeter, if available)
• Insulation tester Note: The winding resistances (coil U, coil V, coil W) of a three-phase induction motor must be identical in order to generate a symmetrical rotating field in the stator. However, even if the winding resistances are identical, it is still possible for insulation faults to occur (winding-to-winding or winding-to-frame). A winding-to-winding insulation fault can result in a short circuit (triggering the circuit breaker) or overcurrent which is then shut off by the motor protection relay or a general motor protection mechanism (NTC, PTC). A winding-to-frame insulation fault can pose a contact hazard since a potential difference arises between the housing or frame and earth. In this case, it is important to install a dependable protective mechanism which disconnects the motor from the mains when hazardous contact voltages (> 50 V) occur. The measured winding resistances should be approximately equal to the following values:
270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).
The insulation resistances must be at least 1 kΩ/V according to VDE specifications. This means that no insulation fault should be present as long as the winding-to-winding resistance
is at least 400kΩ and the resistance between windings and the grounded frame or housing
is at least 230kΩ.
Troubleshooting on electrical machines
42 EEM/F/7 FAULT SWITCHES 4 AND 5 ACTUATED
Measurement procedure
Select a suitable measuring instrument, measure the winding resistance for each of the coils U, V, W and enter the values in the table provided. Winding resistance can be measured with a ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
Coil U (U1-U2)
Coil V (V1-V2)
Coil W (W1-W2)
Select a suitable measuring instrument, measure the winding-to-winding insulation resistance values and enter the values in the table provided. Winding-to-winding insulation resistance can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 – V1
U1 – W1
V1 – W1
U2 – V2
U2 – W2
V2- W2
Troubleshooting on electrical machines
EEM/F/7 FAULT SWITCHES 4 AND 5 ACTUATED 43
Select a suitable measuring instrument, measure the insulation resistance values between
windings and the frame or housing and enter the values in the table provided for this purpose.
The resistance between windings and frame can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 –
V1 –
W1 –
U2 –
V2 –
W2-
Troubleshooting on electrical machines
44 EEM/F/7 FAULT SWITCHES 4 AND 5 ACTUATED
Fill in all the measurements on the following diagram of the motor.
What can be said about the motor windings and insulation?
Troubleshooting on electrical machines
EEM/F/8 FAULT SWITCHES 5 AND 8 ACTUATED 45
Fault switches 5 and 8 actuated
Experiment objectives
Exercises:
• Measurement of winding resistance in a three-phase induction motor with squirrel-cage rotor
• Measurement of insulation resistance in a three-phase induction motor with squirrel-cage rotor
• Identification of winding and/or insulation faults
Open the fault simulator and actuate fault switches 5 and 8 without simulating any other faults. Close the fault simulator again.
Troubleshooting on electrical machines
46 EEM/F/8 FAULT SWITCHES 5 AND 8 ACTUATED
Circuit
U1 V1 W1
W2 U2 V2
M
3~
Sample measurements
U1 V1 W1
W2 U2 V2
Ω
ΩΩ
Terminal panel
Screen terminal
Housing (frame)
Stator coil "W"
Stator coil "V"
Stator coil "U"
Winding-to-winding insulation resistance measurement
Winding-to-frame insulation resistance measurement
Winding resistance measurement
Troubleshooting on electrical machines
EEM/F/8 FAULT SWITCHES 5 AND 8 ACTUATED 47
Equipment/components
• Three-phase induction motor with squirrel-cage rotor
• Multimeter (or ohmmeter, if available)
• Insulation tester Note: The winding resistances (coil U, coil V, coil W) of a three-phase induction motor must be identical in order to generate a symmetrical rotating field in the stator. However, even if the winding resistances are identical, it is still possible for insulation faults to occur (winding-to-winding or winding-to-frame). A winding-to-winding insulation fault can result in a short circuit (triggering the circuit breaker) or overcurrent which is then shut off by the motor protection relay or a general motor protection mechanism (NTC, PTC). A winding-to-frame insulation fault can pose a contact hazard since a potential difference arises between the housing or frame and earth. In this case, it is important to install a dependable protective mechanism which disconnects the motor from the mains when hazardous contact voltages (> 50 V) occur. The measured winding resistances should be approximately equal to the following values:
270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).
The insulation resistances must be at least 1 kΩ/V according to VDE specifications. This means that no insulation fault should be present as long as the winding-to-winding resistance
is at least 400kΩ and the resistance between windings and the grounded frame or housing
is at least 230kΩ.
Troubleshooting on electrical machines
48 EEM/F/8 FAULT SWITCHES 5 AND 8 ACTUATED
Measurement procedure
Select a suitable measuring instrument, measure the winding resistance for each of the coils U, V, W and enter the values in the table provided. Winding resistance can be measured with a ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
Coil U (U1-U2)
Coil V (V1-V2)
Coil W (W1-W2)
Select a suitable measuring instrument, measure the winding-to-winding insulation resistance values and enter the values in the table provided. Winding-to-winding insulation resistance can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 – V1
U1 – W1
V1 – W1
U2 – V2
U2 – W2
V2- W2
Troubleshooting on electrical machines
EEM/F/8 FAULT SWITCHES 5 AND 8 ACTUATED 49
Select a suitable measuring instrument, measure the insulation resistance values between
windings and the frame or housing and enter the values in the table provided for this purpose.
The resistance between windings and frame can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 –
V1 –
W1 –
U2 –
V2 –
W2-
Troubleshooting on electrical machines
50 EEM/F/8 FAULT SWITCHES 5 AND 8 ACTUATED
Fill in all the measurements on the following diagram of the motor.
What can be said about the motor windings and insulation?
Troubleshooting on electrical machines
EEM/F/9 ALL FAULT SWITCHES ACTUATED 51
All fault switches actuated
Experiment objectives
Exercises:
• Measurement of winding resistance in a three-phase induction motor with squirrel-cage rotor
• Measurement of insulation resistance in a three-phase induction motor with squirrel-cage rotor
• Identification of winding and/or insulation faults
Open the fault simulator and actuate all fault switches. Close the fault simulator again.
Troubleshooting on electrical machines
52 EEM/F/9 ALL FAULT SWITCHES ACTUATED
Circuit
U1 V1 W1
W2 U2 V2
M
3~
Sample measurements
U1 V1 W1
W2 U2 V2
Ω
ΩΩ
Terminal panel
Screen terminal
Housing (frame)
Stator coil "W"
Stator coil "V"
Stator coil "U"
Winding-to-winding insulation resistance measurement
Winding-to-frame insulation resistance measurement
Winding resistance measurement
Troubleshooting on electrical machines
EEM/F/9 ALL FAULT SWITCHES ACTUATED 53
Equipment/components
• Three-phase induction motor with squirrel-cage rotor
• Multimeter (or ohmmeter, if available)
• Insulation tester Note: The winding resistances (coil U, coil V, coil W) of a three-phase induction motor must be identical to generate a symmetric rotary field in the stator. However, even if the winding resistances are identical, it is still possible for insulation faults to occur (winding-to-winding or winding-to-frame). A winding-to-winding insulation fault can result in a short circuit (triggering the circuit breaker) or overcurrent which is then shut off by the motor protection relay or a general motor protection mechanism (NTC, PTC). A winding-to-frame insulation fault can pose a contact hazard since a potential difference arises between the housing or frame and earth. In this case, it is important to install a dependable protective mechanism which disconnects the motor from the mains when hazardous contact voltages (> 50 V) occur. The measured winding resistances should be approximately equal to the following values:
270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).
The insulation resistances must be at least 1 kΩ/V according to VDE specifications. This means that no insulation fault should be present as long as the winding-to-winding resistance
is at least 400kΩ and the resistance between windings and the grounded frame or housing
is at least 230kΩ.
Troubleshooting on electrical machines
54 EEM/F/9 ALL FAULT SWITCHES ACTUATED
Measurement procedure
Select a suitable measuring instrument, measure the winding resistance for each of the coils U, V, W and enter the values in the table provided. Winding resistance can be measured with a ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
Coil U (U1-U2)
Coil V (V1-V2)
Coil W (W1-W2)
Select a suitable measuring instrument, measure the winding-to-winding insulation resistance values and enter the values in the table provided. Winding-to-winding insulation resistance can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 – V1
U1 – W1
V1 – W1
U2 – V2
U2 – W2
V2- W2
Troubleshooting on electrical machines
EEM/F/9 ALL FAULT SWITCHES ACTUATED 55
Select a suitable measuring instrument, measure the insulation resistance values between
windings and the frame or housing and enter the values in the table provided for this purpose.
The resistance between windings and frame can be measured with an ___________________________________________________.
Resistance
Measurement 0.1 kW 0.3 kW 1 kW
U1 –
V1 –
W1 –
U2 –
V2 –
W2-
Troubleshooting on electrical machines
56 EEM/F/9 ALL FAULT SWITCHES ACTUATED
Fill in all the measurements on the following diagram of the motor.
What can be said about the motor windings and insulation?
Troubleshooting on electrical machines
FEEDBACK
Working together with you and for you: Your personal experience and observations can contribute to improvements to this product and the elimination of any errors. Your comments will be of considerable importance to us in future revisions of our manuals.
We wish to thank you for your interest and your cooperation.
Reg.: Manual
Notes:
Date:
Copyright © 2007 LUCAS-NÜLLE GmbH. All rights reserved.
This manual is protected by copyright. All rights pertaining thereto are reserved. Any reproduction of this document as a file or in written form be it photocopy, microfilm or any other method or conversion into a machine-compatible language, in particular for data processing systems, without the expressed written approval of the LUCAS-NÜLLE GmbH is strictly forbidden. The one specific exception to the above is the reproduction of worksheets for students to be used entirely within the organisation that has purchased this resource and solely for the purposes of education. Such worksheets may be reproduced in any numbers as long as no alterations to the content are made.
If changes have been performed in a manner which was not strictly authorised by the LUCAS-NÜLLE
GmbH, any product liability or warranty claims pertaining thereto are null and void.
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16
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Telefon +49 2273567-0 · Fax +49 2273567-30
www.lucas-nuelle.de
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