Siemens 1LA2

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
difculty 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
specied.
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.