In order to make a micromotor work, it’s necessary to check its operating condition. But how to check it completely? Here are five aspects to monitor the micromotor operation.
1. Monitor temperature
When the micromotor is running normally, it will heat up and the temperature will rise. If the temperature exceeds the limit allowed, the winding may overheat and burn out. To determine whether the micromotor is overheated, the following methods can be adopted:
1) Hand-touch method: This type of inspection must be performed with an electroscope to find out that the micromotor has no leakage. Touch the micro motor housing with the back of the hand; No hot feeling indicates that the temperature is normal while obvious hot feeling indicates that the motor is overheated.
2) Water test method: Drop two or three drops of water on the outer casing of the micromotor. If there is no sound from the hot air, the micro motor won’t overheat while if the water droplets are rapidly vaporized, accompanied by a “beep” sound, the motor will be overheated.
2. Monitor the power supply
If the three-phase power supply is too high or too low and the voltage is unbalanced, it will have adverse consequences for the operation of the micromotor. General micromotors can operate normally within ±7% of the voltage rating.
1) The difference between the three-phase voltage is too large (more than 5%), which will cause the unbalance of the three-phase current.
2) The circuit has short circuits, grounding, poor contact, and other faults, which will also cause the unbalance of the three-phase voltage of the micromotor.
3) Three-phase micro-motor is in single-phase condition will cause the large unbalance of three-phase voltage, which is a common cause of micro-motor winding burnout and should be monitored.
3. Monitor load current
The load current of the micromotor increase, then its temperature will also increase, but its load current should not exceed the rated value during normal operation.
1) While monitoring whether the load current increases, the balance of the three-phase current should also be monitored.
2) The unbalance of the current of each phase in the normal operation should not exceed 10%.
3) If the difference is very large, the stator winding may cause a short circuit, open circuit, reverse connection, or other single-phase operation of the micromotor.
4. Monitor bearings
The temperature of the bearing in the operation of the micromotor shall not exceed the value that is allowed, and there shall be no oil leakage at the edge of the bearing cover, which causes the overheating of the micro motor bearing. If the condition of the ball bearing deteriorates, the bearing cap and the shaft will be rubbed, the lubricating oil will be too much or too little, the transmission belt will be too tight, or the shaft of the micromotor and the axis of the driven machine will cause too much concentricity error.
5. Monitor vibration, sound and smell
When the micromotor is in the normal operation, there should be no abnormal vibration, sound and smell. Larger micromotors also have a uniform “beep” sound and a whistling sound of the fan.
Electrical faults can also cause vibration and abnormal noise in the micromotor.
1) The current is too large, and the three-phase power is significantly unbalanced.
2) The rotor has broken bars and the load current is unstable. It will emit a high and low “beep” sound, and the body will vibrate.
3) When the temperature of the winding of the micromotor is too high, it will emit a strong smell of insulating paint or the burning smell of the insulating material, and if it is serious, it will emit smoke.