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Motor fault diagnosisMotor fault diagnosis
Fault Fault Probable Probable causecause
After power is on, the motor does After power is on, the motor does notnot
rotate, but without noise, odor orrotate, but without noise, odor or
smoke.smoke.
①①
Power is not on(at least two Power is not on(at least two phase off)phase off)
②②Fuse fusing(at least two phase fusing)Fuse fusing(at least two phase fusing)
③③Overcurrent relay adjusts too smallOvercurrent relay adjusts too small
④④Wiring error of Wiring error of control equipmentcontrol equipment
After power is on, the motor does After power is on, the motor does notnot
rotate and fuse rotate and fuse burnout.burnout.
①①Lack one phase power, or reverse connection ofLack one phase power, or reverse connection of
stator coil one phasestator coil one phase
②②Short circuit of stator windingShort circuit of stator winding；；
③③Grounding of stator windingGrounding of stator winding
④④
Wiring error of Wiring error of stator windingstator winding
⑤⑤Fuse section too Fuse section too small.small.
After power is on, the motor does After power is on, the motor does notnot
rotate with buzzing noise.rotate with buzzing noise.
①①Open circuit of stator, rotor winding(one phaseOpen circuit of stator, rotor winding(one phase
disconnectiodisconnection) or n) or one phase power is one phase power is off.off.
②②
Start and end of the winding outgoing line wronglyStart and end of the winding outgoing line wrongly
connect or internal connect or internal winding oppositely connect.winding oppositely connect.
③③Power return contact loosens and contact resistancePower return contact loosens and contact resistance
is large.is large.
④④
Motor load too large or rotator locks.Motor load too large or rotator locks.
⑤⑤Power voltage too low.Power voltage too low.
⑥⑥
Small motor assembles too tight or bearing greaseSmall motor assembles too tight or bearing grease
too hard.too hard.
⑦⑦
Bearing seizing-up.Bearing seizing-up.
Motor starts hard, and the motorMotor starts hard, and the motor
speed is much lower than ratedspeed is much lower than rated
speed with rated load.speed with rated load.
①①Power voltage too low.Power voltage too low.
②②
△△ Motor wrongly connected to YMotor wrongly connected to Y
③③Cage rotor open weld or crackCage rotor open weld or crack
④④
Local coil of stator and rotor wrongly or oppositelyLocal coil of stator and rotor wrongly or oppositely
connected.connected.
⑤⑤Add too much nAdd too much number of windumber of windings when repings when repair motorair motor
winding.winding.
⑥⑥
Motor overload.Motor overload.
Current is unbalance when motorCurrent is unbalance when motor
without load and three without load and three phases differphases differ
a lot.a lot.
①①When rewind, numbers of stator three-phase windingWhen rewind, numbers of stator three-phase winding
is not equal.is not equal.
②②Two ends of winding wrongly connectedTwo ends of winding wrongly connected
③③Unbalance power voltage.Unbalance power voltage.
④④There is interturn short circuit or coil oppositelyThere is interturn short circuit or coil oppositely
connected in the winding.connected in the winding.
Motor without load, while loaded,Motor without load, while loaded,
ammeter indicator is unstable andammeter indicator is unstable and
swings.swings.
①①
Guide bar of cage rotor open weld or Guide bar of cage rotor open weld or crackcrack
②②Wound rotor fault(one phase open circuit) or badWound rotor fault(one phase open circuit) or bad
brush and collecting ring short circuiting device brush and collecting ring short circuiting device contact.contact.
Motor without load, current isMotor without load, current is
balance, but the value is largebalance, but the value is large
①①Reduce too much number of stator windings whenReduce too much number of stator windings when
repair motor winding.repair motor winding.
②②
Power voltage too high.Power voltage too high.
③③
Y connected motor wrongly connect to ΔY connected motor wrongly connect to Δ
④④
During motor assemble, rotor oppositely connects,During motor assemble, rotor oppositely connects,
make stator core unaligned, effective length shortens.make stator core unaligned, effective length shortens.
⑤⑤Air gap oveAir gap over large or unr large or uneven.even.
⑥⑥
When remove old winding for overhaul, use improperWhen remove old winding for overhaul, use improper
way that burn the iron core.way that burn the iron core.
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