The four simple methods to check the fault of permanent magnet motor include seeing, listening, smelling and touching.
1、 Look: When the permanent magnet motor is running, observe whether it is abnormal. The main phenomena are as follows:
1. When the stator winding is short-circuited, smoke can be seen from the motor.
2. If the motor is seriously overloaded or has phase failure, the speed will slow down and a strong "buzz" will be heard.
3. If the motor operates normally but stops suddenly, you will see that the wire is loose, the fuse is blown, or the parts are jammed to produce sparks.
4. If the motor vibrates violently, the transmission device may get stuck, the motor connection is poor, and the foundation screw is loose.
5. The discoloration, fire and smoke traces at the contact points and connections of the connecting wires in the motor can cause local overheating, poor contact at the wire connections or burning of the windings.
2、 Listen: When the permanent magnet motor operates normally, it should make a steady and slight "buzzing noise" without any noise or special noise. If the noise is too large, including electromagnetic noise, bearing noise, ventilation noise, mechanical friction noise, etc., it may be a precursor or fault phenomenon.
1. If the motor makes high-pitched, low-pitched and strong noise when it hears electromagnetic noise, it may be due to one of the following reasons.
(1) The air gap between the stator and rotor is uneven. At this time, the tone fluctuates, and the distance between high frequency and low frequency remains unchanged. This is caused by bearing wear, which makes the stator and rotor not concentric.
(2) The three-phase current is asymmetrical. This is due to incorrect grounding, short circuit or poor contact of three-phase winding; The dull sound indicates that the motor is seriously overloaded or out of phase.
(3) The iron core is loose. When the motor is running, the iron core fixing screw is loose due to vibration, which causes the iron core silicon steel sheet to fall off and make noise.
2. Pay attention to the bearing noise of permanent magnet motor during operation. The monitoring method is: push one end of the screwdriver onto the bearing seat, and the other end is close to the ear. You can hear the sound of the bearing. During the normal operation of the bearing, the noise is continuous and "grinding" is small, without high and low changes, and without metal friction noise. If the following noise occurs, it is abnormal.
(1) "Squeak" sound can be heard when the camp is running. This is the sound of metal friction, usually caused by the lack of oil in the bearing. Remove the bearing and fill it with proper amount of grease.
(2) If there is a "cool" sound, it is the sound when the ball rotates. This is usually caused by dry fat or lack of oil. You can add proper amount of fat.
(3) If there is a "click" or "squeak" sound, it is the sound generated by the irregular movement of the ball in the bearing. This is caused by the damage of the ball in the bearing or the long-term use of the motor and the drying of the lubricating grease.
3. When the driving mechanism and driven mechanism of the motor emit continuous rather than fluctuating noise, it can be handled under the following conditions:
(1) The periodic "click" is caused by uneven belt connection.
(2) Periodic "boom" noise is caused by the gap between the coupling or pulley and the shaft and the wear of the key or keyway.
(3) The uneven impact noise is caused by the impact of the blades on the fan shroud.
3、 Smell: The fault can be judged and prevented by smelling the smell of permanent magnet motor. If there is a special paint smell, it indicates that the internal temperature of the motor is too high; If there is strong paste or fire smell, the insulation layer may break or the winding may burn out.
4、 Touch: touch the temperature of some parts of the permanent magnet motor to determine the cause of the fault. For safety, please touch the parts around the motor housing and bearing with the back of your hand. If abnormal temperature is detected, it may be due to any of the following reasons:
1. Poor ventilation. If the fan falls off, the air duct is blocked, etc.
2. Overload. The current is too high and the stator winding is overheated.
3. Stator winding inter-turn short circuit or three-phase current asymmetry.
4. Start or brake frequently.
5. If the temperature around the bearing is too high, it may be caused by bearing damage or lack of oil.
