17
Sr.
No.
Trouble
Cause
Remedy
4
Motor starts sluggishly,
speed falls when load
is put on
Rating not proper
Get correct type of motor.
Voltage too low at motor
terminals because of line
drop
- do -
Starting load torque too
high
Check load characteristics with motor
speed torque.
Broken rotor bars
Look for cracks near the ring & if required
get new rotor.
5
Motor starts with
difficulty on star
connection or not at all
Load too high
Reduce load or use larger motor.
Supply voltage low
Check supply lines to motor.
Contacts burnt in star/delta
starter
Overhaul or replace starter.
6
Stator heats up quickly
& takes large no load
current
Stator wrongly connected
Check connection.
Phase short
Rewind
Multiple earth
Rewind
7
Motor overheats while
running on load
Overload
Reduce load.
One phase open
Check connections.
Shorted stator coil
Repair & check wattmeter reading.
Faulty connection
Correct the connections.
Motor operated on load
cycle not in accordance with
the name plate
Run the motor on duty for which it is
specified.
High or low voltage
Check voltmeter reading.
Foreign material in air gap
Dismantle & remove obstruction.
Rotor rubs stator bore
Recondition the rotor. Replace worn out
bearings.
8
Motor vibrates after
connections are made
Motor misaligned
Realign.
Weak foundation
Provide strong base.
Coupling out of balance
Balance coupling.
Driven equipment un-
balanced.
Re-balance.
Balancing weights shifted.
Re-balance the rotor.
Defective bearings
Replace bearings.
Bearings not in line
Line up properly.
Excessive end play
Adjust bearings or add washers. Use
shims for alignment. Use vibration pads to
dampen external vibrations.
9
Scraping noise
Fan touching fan cover
Remove interference.
Loose on bed plates
Tighten mounting bolts.
10 Magnetic noise
Airgap not uniform
Check & correct bearings.
Loose bearings
Correct or replace bearings.
11 Shaft end breaks or
stator rotor rubbing
Excessive radial loads due to
pulley drives
Check for suitability.
12 Heavy vibrations
Load unbalance
Re-balance.
13 Current unbalance
Unbalanced supply voltage
Check voltage.