For customers who want to buy permanent magnet motor, they pay more attention to these problems. One is the characteristics of permanent magnet motor, and the other is its working efficiency. We have introduced the characteristics of this motor before, so how to improve the working efficiency of permanent magnet motor? Let's learn together!
The main factors affecting the working efficiency of permanent magnet motor can be divided into mechanical loss and electromagnetic loss. In order to effectively improve the working efficiency of permanent magnet motor, we must start from the following influencing factors.
First, reduce rotor loss
The loss of permanent magnet motor rotor is mainly related to the rotor resistance and the current passing through the rotor. The main methods to reduce the loss of permanent magnet motor rotor winding are: reduce the resistance of rotor winding, and then increase the slot cross-sectional area of rotor. We can use thicker wires with low resistivity. Nowadays, most of the rotor guide bars of small and medium-sized squirrel cage motors are made of cast aluminum. If copper guide bars are used, the loss can be reduced by 10% ~ 15%.
Second, reduce stator copper loss
Because the electric power on the resistance w = I2R, reducing the resistance value and current can reduce the loss of stator winding. The main methods are:
a. Expand the cross-sectional area of stator slot. Because this operation can reduce the area of the magnetic circuit and increase the magnetic density of the tooth. b. Increase the full slot rate of stator slot. c. Shorten the length of stator winding end as far as possible. It can be seen that reducing the end length of the winding can reduce the resistance value of the stator winding. Generally, the loss at the end of stator winding accounts for 1 / 4 ~ 1 / 2 of the total loss of winding. d. Rare earth permanent magnet synchronous motor is developed. Eliminating the excitation winding and excitation current can not only simplify its structure, but also improve the working efficiency and power factor.
Third, reduce electronic iron loss
The methods to reduce the iron loss of permanent magnet motor are as follows: A. select cold-rolled silicon steel sheet. The selection of cold-rolled silicon steel sheet with excellent magnetic conductivity, stable quality and low loss can significantly reduce the hysteresis loss and conveniently reduce the thickness of silicon steel sheet, so as to reduce the eddy current loss. b. Reduce the magnetic density. Reduce the density of magnetic flux by increasing the length of iron core. c. Use the insulating coating of iron chip with superior performance. d. Use advanced heat treatment and manufacturing technology. After cold-rolled silicon steel sheet is processed by punching, shearing and bending, it will produce certain mechanical stress and strain, and the magnetism will change with, resulting in the increase of iron loss. Therefore, it is necessary to heat treat it to restore its original magnetism, which can reduce the loss by 10% ~ 20%. At the same time, we should speed up the development of new cold-rolled silicon steel sheet, so that the iron loss changes little after it is processed into iron core.
Fourth, reduce the stray loss of permanent magnet motor
The stray loss of permanent magnet motor is mainly caused by the high-frequency loss of high-order harmonic of magnetic field in stator and rotor winding and iron core. Generally, it accounts for 0.5% ~ 3% of the input power. The main methods to reduce stray loss are: A. improve the design of stator winding and reduce harmonics. b. Improve the cutting method of the outer surface of the rotor and the insulation treatment of the inner surface of the rotor slot. c. Magnetic slot mud or magnetic slot wedge is used to replace the traditional insulating slot wedge, so as to weaken the cogging effect and reduce the additional stray loss accordingly.
Fifth, reduce ventilation friction loss
Because the high-efficiency motor adopts measures such as selecting high-quality materials and optimizing design, the temperature rise of the motor is relatively low, so the size of the fan can be appropriately reduced. Of course, the ventilation structure can also be designed reasonably. We can choose axial flow fan or backward inclined fan. In addition, we can also use higher quality bearings.
