A permanent magnet motor is a DC motor in which the designated rotor is a permanent magnet and only the rotor is a coil. Once the permanent magnet motor loses its magnetism, it can basically only choose to replace the motor. If it is repaired, the cost is higher. So how do we see the motor loses magnetism?
1. When the machine starts running, the current is normal. After a period of time, the current becomes larger. After a long time, the inverter will be overloaded.
First of all, it is necessary to confirm that the inverter of the air compressor manufacturer is selected correctly, and then confirm whether the parameters in the inverter have been changed. If there is no problem with both, it is necessary to judge by the back electromotive force, disconnect the machine head from the motor, perform no-load identification, and run at no-load to the rated frequency. At this time, the output voltage is the back electromotive force, if it is lower than the motor nameplate. The motor can be demagnetized by the back electromotive force of 50V or more.
2. The running current of the permanent magnet motor after demagnetization will generally exceed the rated value. Those that report overload only when running at low speed or high speed or occasionally report overload are generally not caused by demagnetization.
3, permanent magnet motor demagnetization is a certain time, some months or even a year or two. If the manufacturer selects the wrong type and causes the current to be overloaded, it is not the motor demagnetization.