1. What is a permanent magnet motor
Permanent magnet motor is a kind of high efficiency and energy saving motor that uses permanent magnet materials to generate magnetic field without excitation current and excitation winding, saving energy and simplifying motor structure

2. Why does permanent magnet motor save electricity compared with asynchronous motor
The rotor of permanent magnet motor has no copper loss
The air gap of permanent magnet motor is larger than that of asynchronous motor, which leads to the reduction of stray loss
The reduction of loss and the increase of power factor reduce stator current and stator copper loss
The substantial reduction of various losses leads to the real energy saving and power saving of the permanent magnet motor

3. Why does a permanent magnet motor run better with a frequency converter
When the motor is directly connected to the power supply for starting, the starting instantaneous current is large, which will have a great impact on the power grid. If the inverter is equipped for operation, the motor will start stably, the starting current is small, and the power grid will not be greatly impacted. This not only protects the power grid, but also protects the motor well
The motor is controlled by the frequency converter. The frequency converter can be adjusted according to the user's actual working load to achieve good operation effect, which will save more electricity

4. Will the permanent magnet motor demagnetize during use
Normal use will not demagnetize, and the service life is the same as that of ordinary motors. Users should pay attention to that when the motor is overloaded or overheated, the coil will be burnt and the permanent magnet will be demagnetized

5. Motor bearing temperature regulations, causes and handling of abnormalities
According to the regulations, the high temperature of rolling bearing shall not exceed 95 ℃ and that of sliding bearing shall not exceed 80 ℃. And the temperature rise shall not exceed 55 ℃ (the temperature rise is the bearing temperature minus the ambient temperature during the test)

For details, see HG25103-91, Causes and Treatment of Excessive Bearing Temperature Rise:
(1) Cause: The shaft is bent and the centerline is inaccurate. Handling: find the center again
(2) Cause: foundation screws are loose. Handling: Tighten the foundation screws
(3) Cause: The lubricating oil is not clean. Treatment: change the lubricating oil
(4) Cause: The lubricating oil has been used for a long time and has not been replaced. Treatment: Clean the bearing and replace the lubricating oil
(5) Cause: The ball or roller in the bearing is damaged. Treatment: Replace the bearing with a new one
According to the national standard, Class F insulation and Class B assessment, the motor temperature rise is controlled at 80K (resistance method) and 90K (element method). Considering the ambient temperature of 40 ℃, the high temperature of motor operation shall not exceed 120/130 ℃. 95 ℃ is allowed for high bearing temperature. The temperature of the outdoor surface of the bearing is measured with an infrared detection gun. In experience, the high point temperature of the 4-pole motor cannot exceed 70 degrees. For the motor body, no monitoring is required. After the motor is manufactured, its temperature rise is generally fixed and will not change or increase with the motor operation. The bearing is a vulnerable part and needs to be tested

6. Why do servo motors operate more reliably and have less noise and vibration than ordinary motors
Because the servo motor is smaller and lighter than the traditional motor, the body casting is thickened, and the motor center is high and low, the noise and vibration during operation are very small, the reliability is high, and the maintenance cost is low. There is basically no need for maintenance, which greatly reduces the maintenance cost

7. The material of permanent magnet motor is optimized and its performance is improved compared with that of asynchronous motor
The low loss and high efficiency silicon steel sheet WW350 material is used, while the asynchronous motor uses silicon steel sheet WW800 material, which greatly reduces the iron loss of the motor, and the unit weight loss is reduced by about 60%
Class H high temperature resistant enamelled wire is used, and the allowable working temperature is 180 ℃, while class F ordinary enamelled wire is used for asynchronous motor, and the allowable temperature is only 155 ℃
The permanent magnet adopts NdFeB permanent magnetic material, which is a permanent magnetic material with strong magnetic properties at present, high temperature resistance and strong mechanical properties

8. Comparison of energy efficiency curves between permanent magnet motor and asynchronous motor

From the efficiency curve and power factor curve comparison between the permanent magnet motor and the asynchronous motor in the above figure, it can be seen that the permanent magnet motor can maintain high efficiency under different loads, while the asynchronous motor cannot. When the load is less than 70%, the efficiency drops linearly, and the efficiency is very low. Because the load of the motor will be different in actual operation, the permanent magnet motor can always maintain high efficiency under different loads, The asynchronous motor generally runs at low efficiency, so it consumes electricity

9. The motor will be burnt out in case of interphase short circuit of stator winding
In case of interphase short circuit in the stator winding of the motor, the winding will often be burnt and short circuited, the nearby insulation will be burnt, the motor will generate heat or smoke, and the melt will be burnt out in severe cases. The main causes of the interphase short circuit of the stator winding are as follows: the insulation block of the winding turn to turn or end interphase block is not well padded; The lead out bushing of winding or the wiring bushing between coil groups is not well sleeved; Damping and aging of winding insulation; The winding is mechanically damaged, which may be caused by the damage of the winding, which may puncture the insulation, or the quality defect of the insulating material itself; The motor is overheated and the power supply voltage is too high

10. Motor maintenance
Maintenance process of motor maintenance center: cleaning stator and rotor -- replacing other parts -- vacuum class F pressure impregnation -- drying -- dynamic balance calibration
1. The operating environment should always be kept dry, the motor surface should be kept clean, and the air inlet should not be obstructed by dust, fiber, etc
2. When the thermal protection of the motor acts continuously, find out whether the fault is from the motor or overload or the setting value of the protection device is too low. After the fault is eliminated, the motor can be put into operation
3. The motor shall be well lubricated during operation. Generally, the motor runs for about 5000 hours, that is, the lubricating grease should be supplemented or replaced. If the bearing is overheated or the lubrication deteriorates during operation, the hydraulic pressure should replace the lubricating grease in time. When replacing the lubricating grease, the old lubricating oil shall be removed, and the oil grooves of the bearing and bearing cover shall be cleaned with gasoline, and then ZL-3 lithium base grease shall be filled into 1/2 (for the second pole) and 2/3 (for the fourth, sixth, and eighth poles) of the cavity between the inner and outer rings of the bearing
4. When the service life of the bearing ends, the vibration and noise of the motor will increase significantly. When the radial clearance of the bearing reaches the following value, the bearing shall be replaced
5. When disassembling the motor, take out the rotor from the shaft extension end or non extension end. If it is unnecessary to remove the fan, it is more convenient to take out the rotor from the non shaft extension end. When taking out the rotor from the stator, the stator winding or insulation shall be prevented from being damaged
6. When replacing the winding, the form, size, turns, wire gauge, etc. of the original winding must be recorded. When these data are lost, they should be obtained from the manufacturer. The original design winding can be changed at will, which often worsens the performance of one or more items of the motor, even makes it unusable.