Teco Installation and Maintenance Manual
TEFC Squirrel Cage Induction Motors
Teco Electric and Machinery Company
Manual Number: IOM ~ TEFC Rev.01
5.6. ODOUR.
5.6.1. Causes of motor odours:
i. Short circuit or over current causing overheating of varnish.
ii. Poor lubrication due to insufficient or contaminated grease.
5.7. MEASUREMENT OF THREE PHASE CURRENT.
5.7.1. Causes & effects
When load current is above the rating on the nameplate, it means the
motor may be overloaded. However, the cause of over current is not
confined to overloading, but may be caused by poor coupling installation,
transmission structure, excessive high or low voltage, etc.
a. Causes of unbalanced three phase current.
i. Unbalanced three phase voltage.
ii. Open circuit in power distribution lines.
iii. Poor switch contact.
iv. Open or short circuit in winding.
v. Open circuit at power transformer.
b. Effects:
i. Overheating of the windings causing fire or short circuit.
ii. Vibration of motor.
iii. Reduction of motor output torque.
c. Causes of wavering of ammeter indicator:
The characteristics of devices such as compressor or press are apt to cause
wavering of the indicator. Other causes are,
i. Poor contact of switches.
ii. Uneven mechanism.
iii. Unbalanced air gap due to serious bearing aberration.
iv. Broken conductors of squirrel cage rotor.
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