eemf troubleshooting on electrical machines

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




All fault switches actuated................................................................................................................. 51


EEM/F TABLE OF CONTENTS


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


2 EEM/F EQUIPMENT


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


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



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.



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


U1 – V1

U1 – W1

V1 – W1

U2 – V2

U2 – W2

V2- W2



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


U1 –

V1 –

W1 –

U2 –

V2 –

W2-



Fill in all the measurements on the following diagram of the motor.

What can be said about the motor windings and insulation?


EEM/F/2 FAULT SWITCH 2 ACTUATED 9

Fault switch 2 actuated


Exercises:




Open the fault simulator and actuate fault switch 2 without simulating any other faults. Close the fault simulator again.


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-frame insulation resistance measurement

Winding resistance






• 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).



is at least 230kΩ.




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


Coil U (U1-U2)

Coil V (V1-V2)

Coil W (W1-W2)


Resistance


U1 – V1

U1 – W1

V1 – W1

U2 – V2

U2 – W2

V2- W2






Resistance


U1 –

V1 –

W1 –

U2 –

V2 –

W2-





Exercises:




Open the fault simulator and actuate fault switch 5 without simulating any other faults. Close the fault simulator again.



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"










270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).



is at least 230kΩ.




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


Coil U (U1-U2)

Coil V (V1-V2)

Coil W (W1-W2)


Resistance


U1 – V1

U1 – W1

V1 – W1

U2 – V2

U2 – W2

V2- W2



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.


Resistance


U1 –

V1 –

W1 –

U2 –

V2 –

W2-





Exercises:




Open the fault simulator and actuate fault switch 11 without simulating any other faults.

Close the fault simulator again.



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"










270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).



is at least 230kΩ.





Resistance


Coil U (U1-U2)

Coil V (V1-V2)

Coil W (W1-W2)


Resistance


U1 – V1

U1 – W1

V1 – W1

U2 – V2

U2 – W2

V2- W2






Resistance


U1 –

V1 –

W1 –

U2 –

V2 –

W2-


EEM/F/5 FAULT SWITCHES 1 AND 4 ACTUATED 27

Fault switches 1 and 4 actuated


Exercises:




Open the fault simulator and actuate fault switches 1 and 4 without simulating any other faults. Close the fault simulator again.


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"










270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).



is at least 230kΩ.





Resistance


Coil U (U1-U2)

Coil V (V1-V2)

Coil W (W1-W2)


Resistance


U1 – V1

U1 – W1

V1 – W1

U2 – V2

U2 – W2

V2- W2






Resistance


U1 –

V1 –

W1 –

U2 –

V2 –

W2-





Exercises:







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"










270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).



is at least 230kΩ.





Resistance


Coil U (U1-U2)

Coil V (V1-V2)

Coil W (W1-W2)


Resistance


U1 – V1

U1 – W1

V1 – W1

U2 – V2

U2 – W2

V2- W2






Resistance


U1 –

V1 –

W1 –

U2 –

V2 –

W2-





Exercises:







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"










270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).



is at least 230kΩ.





Resistance


Coil U (U1-U2)

Coil V (V1-V2)

Coil W (W1-W2)


Resistance


U1 – V1

U1 – W1

V1 – W1

U2 – V2

U2 – W2

V2- W2






Resistance


U1 –

V1 –

W1 –

U2 –

V2 –

W2-





Exercises:







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"










270 Ω (0.1 kW), 100 Ω (0.3 kW), 20 Ω (1 kW).



is at least 230kΩ.





Resistance


Coil U (U1-U2)

Coil V (V1-V2)

Coil W (W1-W2)


Resistance


U1 – V1

U1 – W1

V1 – W1

U2 – V2

U2 – W2

V2- W2






Resistance


U1 –

V1 –

W1 –

U2 –

V2 –

W2-


EEM/F/9 ALL FAULT SWITCHES ACTUATED 51

All fault switches actuated


Exercises:




Open the fault simulator and actuate all fault switches. Close the fault simulator again.


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"









• 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).



is at least 230kΩ.





Resistance


Coil U (U1-U2)

Coil V (V1-V2)

Coil W (W1-W2)


Resistance


U1 – V1

U1 – W1

V1 – W1

U2 – V2

U2 – W2

V2- W2






Resistance


U1 –

V1 –

W1 –

U2 –

V2 –

W2-


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.

LUCAS-NÜLLE Lehr- und Meßgeräte GmbH Address: Siemensstraße 2 • D-50170 Kerpen (Sindorf) Postal address: Postfach 11 40 • D-50140 Kerpen Tel.: 02273 / 567-0 • Fax: 02273 / 567-30 • E-mail: [email protected]

16

Lucas-Nülle Lehr- und Meßgeräte GmbHSiemensstraße 2 · D-50170 Kerpen-Sindorf

Telefon +49 2273567-0 · Fax +49 2273567-30

www.lucas-nuelle.de

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