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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-
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.
Motor without load, current is balance, but
the value is large
Reduce too much number of
stator windings when repair
motor winding.
Power voltage too high.
During motor assemble, rotor oppositely connects, make
stator core unaligned, effective length shortens.
Air gap over large or uneven.
When remove old winding for overhaul, use improper way that
burn the iron core.
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