Globus Electric
Motor Services

". . . you can have Service or Excuses, we give Service!"

Motor Failures

The Following Are Typical Causes of
Winding Failures in Three-Phase Motors

Poor operating conditions-environmental, electrical, or mechanical-can dramatically shorten the life of your three-phase stator windings. The failures illustrated below are typical of what can happen in these situations. We show them here to help you identify the causes of failure, so that you may take preventive measures.

Click on the images for a closer look

Compare this new stator winding (right) with the failed windings pictured below.

Winding Single-Phased
(Wye-Connected)

A single-phased winding failure is the result of an open in one phase of the power supply to the motor. The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections.

Winding Single-Phased
(Delta-Connected)

A single-phased winding failure is the result of an open in one phase of the power supply to the motor. The open is usually caused by a blown fuse, an open contactor, a broken power line or bad connections.

Winding Shorted Phase-to-Phase

This type of insulation failure is usually caused by contaminants, abrasion, vibration or voltage surges.

Winding Shorted Turn-to-Turn

This type of insulation failure is usually caused by contaminants, abrasion, vibration or voltage surges.

Winding With Shorted Coil

This type of insulation failure is usually caused by contaminants, abrasion, vibration or voltage surges.

Winding Grounded At Edge Of Slot

This type of insulation failure is usually caused by contaminants, abrasion, vibration or voltage surges.

Winding Grounded At Edge Of Slot

This type of insulation failure is usually caused by contaminants, abrasion, vibration or voltage surges.

Winding Grounded In The Slot

This type of insulation failure is usually caused by contaminants, abrasion, vibration or voltage surges.

Shorted Connection

This type of insulation failure is usually caused by contaminants, abrasion, vibration or voltage surges.

Phase Damage Due To Unbalanced Voltage

Thermal deterioration of insulation in one phase of the stator winding can result from unequal voltage between phases. Unequal voltages usually are caused by unbalanced loads on the power source, a poor connection at the motor terminal, or a high resistance contact (weak spring).

Note: A one-percent voltage unbalance may result in a six- to ten-percent current unbalance.

Winding Damage Due To Overload

Thermal deterioration of the insulation in all phases of the stator winding typically is caused by load demands exceeding the rating of the motor.

Note: Under-voltage and over-voltage (exceeding NEMA standards) will result in the same type of insulation deterioration.

Damage Caused By Locked Rotor

Severe thermal deterioration of the insulation in all phases of the motor normally is caused by very high currents in the stator winding due to a locked rotor condition. It may also occur as a result of excessive starts or reversals.

Winding Damaged By Voltage Surge

Insulation failures like this are usually caused by voltage surges. Voltage surges are often the result of switching power circuits, lightning strikes, capacitor discharges and solid-state power devices.

Green energy today,

for a blue sky tomorrow!

A Friendly Reminder From Globus Electric Inc. Preventative Maintenance will catch your problems before they cost you time.

Copyright 2001-2010 Globus Electric Inc.^©

This Web-site Designed and Maintained by E&A Marketing. All Rights Reserved.