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AC Motor fault diagnosis
Fault Probable cause
After power is on, the motor does not
rotate, but without noise, odor or
smoke.
Power is not on(at least two phase off)
Fuse fusing(at least two phase fusing)
Overcurrent relay adjusts too small
Wiring error of control equipment
After power is on, the motor does not
rotate and fuse burnout.
Lack one phase power, or reverse connection of stator
coil one phase
Short circuit of stator winding
Grounding of stator winding
Wiring error of stator winding
Fuse section too small.
After power is on, the motor does not
rotate but with buzzing noise.
Open circuit of stator, rotor winding(one phase
disconnection) or one phase power is off.
Start and end of the winding outgoing line wrongly
connect or internal winding oppositely connect.
Power return contact loosens and contact resistance is
large.
Motor load too large or rotator locks.
Power voltage too low.
Small motor assembles too tight or bearing grease too
hard.
Bearing seizing-up.
Motor starts hard, and the motor
speed is much lower than rated
speed with rated load.
Power voltage too low.
Motor wrongly connected to Y
Cage rotor open weld or crack
Local coil of stator and rotor wrongly or oppositely
connected.
Add too much number of windings when repair motor
winding.
Motor overload.
Current is unbalance when motor
without load and three phases differ a
lot.
When rewind, numbers of stator three-phase winding is
not equal.
Two ends of winding wrongly connected
Unbalance power voltage.
There is interturn short circuit or coil oppositely
connected in the winding.
Motor without load, while loaded,
ammeter indicator is unstable and
swings.
Guide bar of cage rotor open weld or crack
Wound rotor fault(one phase open circuit) or bad brush
and collecting ring short circuiting device contact.
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