78
AC Motor fault diagnosis
Fault Probable cause
After power is on, the motor does not
rotate, but without noise, odor or
smoke.
①Power is not on(at least two phase off)
②Fuse fusing(at least two phase fusing)
③Overcurrent relay adjusts too small
④Wiring error of control equipment
After power is on, the motor does not
rotate and fuse burnout.
①Lack one phase power, or reverse connection of
stator coil one phase
②Short circuit of stator winding
③Grounding of stator winding
④Wiring error of stator winding
⑤Fuse section too small.
After power is on, the motor does not
rotate but with buzzing noise.
①Open circuit of stator, rotor winding(one phase
disconnection) or one phase power is off.
②Start and end of the winding outgoing line wrongly
connect or internal winding oppositely connect.
③Power return contact loosens and contact resistance
is large.
④Motor load too large or rotator locks.
⑤Power voltage too low.
⑥Small motor assembles too tight or bearing grease
too hard.
⑦Bearing seizing-up.
Motor starts hard, and the motor
speed is much lower than rated
speed with rated load.
①Power voltage too low.
②△Motor wrongly connected to Y
③Cage rotor open weld or crack
④Local coil of stator and rotor wrongly or oppositely
connected.
⑤Add too much number of windings when repair motor
winding.
⑥Motor overload.
Current is unbalance when motor
without load and three phases differ a
lot.
①When rewind, numbers of stator three-phase winding
is not equal.
②Two ends of winding wrongly connected
③Unbalance power voltage.
④There is interturn short circuit or coil oppositely
connected in the winding.
Motor without load, while loaded,
ammeter indicator is unstable and
swings.
①Guide bar of cage rotor open weld or crack
②Wound rotor fault(one phase open circuit) or bad
brush and collecting ring short circuiting device contact.
To Next Page