Common Faults and Solutions of Synchronous Motors

1. Cannot start or the speed is low

  1) The circuit breaker is faulty and the gate cannot be closed.

  Analyze and deal with the closing power supply and closing circuit faults.

  2) The relay malfunctioned.

  If the vibration or set value of the relay is small, check the relay.

  3) One phase of the stator winding or the main circuit is open.

  Check and measure the stator winding and mainline after a power failure, find out the breaking point and repair it.

  4) The load is too heavy or the machinery being pulled is faulty.

  Check the motor load and the machinery being pulled.

2. Not synchronized after startup

  1) The grid voltage is low.

  Check grid voltage.

  2) The auxiliary contact of the circuit breaker connected to the excitation device is poorly closed.

  Check the power outage and repair the auxiliary contacts of the circuit breaker.

  3) The rotor circuit is in poor contact or open circuit.

  Measuring the resistance of the rotor circuit should meet the requirements, and carry out fastening inspection.

  4) The brushless excitation system is faulty, the silicon tube is damaged and there is no output.

  Replace the silicon tube.

  3. Out of step during operation

  1) The power grid voltage is low, and the out-of-step setting thyristor device is out of control.

  Check the SCR out-of-step protection device.

  2) The excitation voltage is reduced.

  Shut down and check the excitation device.

  3) The mechanical load is too heavy.

  Shutdown to check mechanical load.

  4. Sparks and smoke appear in the air gap

  1) The shaft center is not correct or the bearing bush is worn so that the stator and the rotor rub against each other.

  Shut down to check the air gap between the stator and rotor and make corresponding repairs according to the situation.

  2) The rotor is broken or the short circuit ring is desoldered.

  Stop the machine to find out the break point or re-weld the poor contact part.

  3) Turn-to-turn short circuit or phase-to-phase short circuit of the stator winding; rotor coil disconnection or grounding.

  Pull the core to check and replace the faulty coil.

5. Overheating during operation

  1) Overload

  Reduce the mechanical load so that the stator current does not exceed the rated value, monitor the system voltage, current, and    power factor, and adjust in time.

  2) The insulation between the stator core silicon steel sheets is poor or there are burrs.

  Shut down to overhaul the stator core.

  3) There is a short circuit or ground fault in the stator winding.

  Find the faulty coil and repair or replace it.

  4) The ambient temperature is too high and the motor is not well ventilated.

  Check whether the air duct is unblocked, whether the fan is in good condition, and whether the rotation direction is correct.

  5) The water cooler has no water or the water volume is very small.

  Check whether the water cooling system is normal.

  6. Accident parking

  1) Cable or cable head wiring failure.

  Find out the fault point for overhaul.

  2) The stator winding is short-circuited or grounded between phases.

  Find the short circuit or grounding point, deal with the faulty coil, and the withstand voltage is qualified.

  3) The secondary circuit of the current transformer is faulty.

  Check the secondary circuit of the current transformer, deal with disconnection or poor contact, and verify the volt-ampere    characteristic curve of the current transformer.

  4) The relay malfunctions.

  Re-check relay settings and adjust relays.

  5) The shaft of the motor is locked or the dragged machinery is stuck.

  Find and fix mechanical problems.

  6) The excitation device or excitation circuit is faulty.

  Check and debug the excitation device to eliminate poor contact of the excitation circuit.

  7) Process interlocking action.

  Judging the action part of the process interlocking device, finding out the cause, eliminating it and doing a simulation test.

  7. Severe vibration

  1) Poor mechanical alignment.

  Re-align and meet technical requirements.

  2) The bearing is damaged.

  Replace motor bearings.

  3) The static balance and dynamic balance of the rotor are unqualified.

  Adjust the dynamic and static balance of the rotor.

  4) The foundation of the motor is uneven and the anchor screws are loose.

  Check the foundation level and tighten the anchor screws.