2025-06-09
Electrical failure
Short circuit, open circuit of stator and rotor windings, and failure of starting equipment;
Mechanical failure
Excessive vibration, overheating of bearings, friction between stator and rotor, and abnormal noise, etc.
Phenomenon: no sound and no rotation
①First use a multimeter to check the voltage at the permanent magnet motor terminal. If there is no voltage or only one-phase voltage, it means that the power supply is not connected or the power supply is faulty;
②If the three-phase voltage at the permanent magnet motor terminal is basically balanced, it means that there is a problem with the wiring of the permanent magnet motor stator winding. The most likely possibility is that the neutral point is not connected properly or the lead wire is not connected properly.
Phenomenon: After the power is turned on, the permanent magnet motor only hums but does not rotate
The power supply must be disconnected immediately, and then the cause must be carefully found
①Check whether the machine part is stuck. This kind of fault is checked before starting the motor to see if the permanent magnet motor can rotate gently.
②The power supply voltage is too low. It is difficult to start the permanent magnet motor with too low power supply voltage. It can be found as long as the power supply voltage and the wiring method of the permanent magnet motor are measured.
Phenomenon: After the motor is powered on, the fuse blows quickly (or the overcurrent protection is activated)
① Check that the rated current of the fuse does not match the capacity of the permanent magnet motor;
② The line between the permanent magnet motor power supply and the terminal has a phase-to-phase short circuit or a short circuit to the ground. Turn off the power switch, disassemble the permanent magnet motor terminal, and use a megohmmeter to check and find out;
③ The stator winding or lead wire of the permanent magnet motor has a phase-to-phase short circuit or is grounded.
④ After the permanent magnet motor is started, it cannot be pulled into the synchronous speed. Pay special attention when starting a large inertia load.
Permanent magnet motors often have some abnormal operation phenomena during operation, such as: permanent magnet motor vibration, permanent magnet motor overload, permanent magnet motor abnormal sound, bearing and coil temperature increase, current increase and speed change, etc. Although these abnormalities will not cause the permanent magnet motor protection to trip, they have affected the safe operation of the permanent magnet motor. If some important permanent magnet motors with abnormal operation are not handled in time, they will not only cause the permanent magnet motor itself to fail, but also cause major accidents such as shutdown.
Phenomenon: The current meter indicates rising or zero; the temperature of the permanent magnet motor body rises, and the vibration increases and the sound is abnormal.
Handling: The missing phase operation of the permanent magnet motor is the operation mode when one phase of the circuit is disconnected due to some reason. First check whether it is the power supply missing phase or the permanent magnet motor stator circuit fault. One way to prevent the permanent magnet motor from running with missing phase is to rely on the judgment of the duty officer and deal with it in time after discovery; the second is to install a missing phase protector in the permanent magnet motor circuit.
Phenomenon: The body temperature and temperature rise of the permanent magnet motor during operation are significantly higher than those during normal operation, and the current increases.
Handling:
① Check whether the mechanical load is rubbing or stuck;
② Check whether the mechanical load is increasing. If so, the load should be reduced until the temperature is stable;
③ Check whether the ventilation system of the permanent magnet motor is faulty, and the load should be reduced at the same time;
④ Check whether the current of each phase of the permanent magnet motor is balanced to determine whether the stator winding is faulty or running with missing phase.
①The permanent magnet motor is inconsistent with the mechanical center;
②The permanent magnet motor rotor is unbalanced;
③The permanent magnet motor bearing is damaged;
④The permanent magnet motor foundation strength is insufficient or the anchor screws are loose;
⑤The permanent magnet motor is running in a phase-missing state. If the vibration of the permanent magnet motor exceeds the allowable value range, the permanent magnet motor should be stopped immediately.
①Mechanical reasons of permanent magnet motor: abnormal bearing sound, such as oil shortage, should be refueled immediately; if the bearing is damaged, it should be stopped immediately;
②Electrical reasons: check whether the voltage and frequency are normal; check whether the three-phase stator current is balanced, and determine whether there is a broken line or a turn-to-turn short circuit inside the burning group.
The reasons for the burnout of permanent magnet motors can be summarized as: load, power supply, motor insulation, and phase loss.
Load (overload)
Overload operation causes the motor to heat up. Or the motor starts frequently, causing the motor to overheat. This kind of burnout will cause both ends of the motor's stator and rotor to burn black, and the burnt black parts are relatively uniform (generally, motors have a certain operating power, called rated power, in watts (W). If the actual power used by the motor exceeds the rated power of the motor under certain circumstances, this phenomenon is called motor overload).
Power supply
The voltage is too low and the load is under rated conditions, the current increases, and the motor overheats. The power supply voltage is too high, and the motor burns. Or the motor runs in a phase-missing manner. This situation is relatively rare and easy to judge. The main reason is that there are traces of burns in the circuit.
Insulation
The internal insulation of the motor does not meet the standard, and there is a turn-to-turn short circuit. Or the internal wiring is wrong. This kind of burnout is sometimes easily confused with overload burnout. The stator and rotor will also burn black, but there will be obvious burnout marks at the short-circuit part, such as copper plating sometimes, and the winding is severely burned locally.
Phase-missing burnout
The permanent magnet motor is a star (Y) connection method: two-phase windings will burn out, and the insulation damage of the two-phase windings to the ground can be measured with a megohmmeter (shaking meter).