Maintenance and Troubleshooting for Three-Phase Induction Motors

Question 1

Why is it important to ensure unrestricted airflow around the motor?

Answer 1

Air flow is important to proper cooling of motor. If restricted, motor may overheat and damage the insulation

Question 2

Is too much grease better than too little grease on the brings of motors?

Answer 2

No. Too little is better since too much may damage the insulation

Question 3

As a general rule, what minimum resistance is acceptable for a low-voltage motor?

Answer 3

Greater than 1 megohm

Question 4

What might cause excessive vibration?

Answer 4

Misaligned motor and load

Question 5

When taking an insulation-resistance test with a megger, the pointer first dips down to low resistance and then slowly rises. Is this cause for concern? Give reasons.

Answer 5

No. Initial dip is likely caused by capacitive charging between the winding being tested and ground.

Question 6

True or False. To clean dust out of some motors it is better to use a vacuum cleaner than compressed air.

Answer 6

True

Question 7

List four senses that should be used when inspecting motors.

Answer 7

Sight, sound, touch and smell