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11. POSSIBLE FAILURES AND INTERFERENCES AT WORK OF SQUIRREL-
CAGE INDUCTION MOTORS AND THEIR REMEDYING
FAILURE
/
INTERFERENCE
SYMPTOMS
POSSIBLE CAUSE
HOW TO CURE / REMEDY
Motor
cannot run
up,
no noise at
all or the
humming is
strong
-Supply interrupted, one of feeder lead
broke, lines broke, for example one
over the fuse
-Stator winding circuit interrupted,
disconnection in Y/D switch, motor
protection fallen out
-Damaged bearings
-Improper connecting
-Main or auxiliary phase interrupted
-Check fuses, motor switch or contactor
or protection circuit breaker…
-Separate supply leads, check the
winding on terminal plate terminals, check
the elements of electrical protection
-Change the bearings
-Connect the motor acc. to appropriate
instructions
-Winding repair or change
Motor cannot accelerate
under load, or accelerate
hardly, sudden drop of
rotational speed under
load
-Load torque too high (overload)
-Motor intended for D connection,
but Y connected
-Supply voltage too low
-Faulty feeder lead
-Rotor squirrel stick or short-
circuit ring interrupted
-Must be in accordance with
motor frame size
-Apply the regular way of motor
connecting
–Stabilize the supply voltage
-Check the supply rightness
-Change the rotor
At start, fuse
blows
or
protection circuit
breaker
switches-off
-Feeder leads from motor switch to
motor are in short circuit
-Two phases of stator winding are in
short circuit or earth connected
-Wrongly chosen/adjusted motor
protection
-Separate and insulate the leads
-Separate the motor from supply
probably it is necessary to be
rewound
-Choose/adjust motor protection
properly
Motor warming in
operation is high
scraping noises ,
motor protection
is
switching-off
after some time
-Motor overload
-Too high or too low supply voltage
-Too high motor switching-on
intensity
-Motor work on single phase
-Rotor scraps on to stator
-Measure the motor current. If it is far
too high in comparison to the rated
one, cure the overload cause
-Stabilize the supply voltage
-Lower the switching-on intensity
-Check supply leads
-Rotor or motor need to be repaired
Motor warming is high
even under no load, pulls
high current, humms,
(1ph motors - thermal
protection is switching-
off)
-Wrong
stator
winding
connection
-Supply voltage to high
-Insufficient cooling
-Short circuit between winding
coils or motor mass
-Connect motor properly acc. to
nameplate data and appropriate
instructions
-Stabilize the supply voltage
-Assure undisturbed air flow to and
around the motor
-Change of winding
Motor
in
operation
causes
increased and
abnormal noise
-Electrical reasons
-Bearing damage
-Damage in gearbox mounted
on
-Rotor unbalanced
-Insufficient fixing on the
ground or flange
-Friction disc scraps
-Consult the manufacturer
-Change the bearings
-Check the gearbox
-Rebalance dynamically the rotor of drive
-Tighten the appropriate screws with adequate
torque
-Check the air gap or wear-off of friction disc
lining
