How to improve the working efficiency of permanent magnet motors

For customers who want to buy a permanent magnet motor, they are only concerned about these issues. One is the characteristics of the 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 the permanent magnet motor? Let’s learn together below!

The main factors affecting the working efficiency of permanent magnet motors can be divided into: mechanical losses and electromagnetic losses. In order to effectively improve the working efficiency of permanent magnet motors, we must start from the following influencing factors.

1. Reduce rotor losses

The loss of the 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 the permanent magnet motor rotor winding are: reducing the resistance of the rotor winding, and then increasing the slot cross-sectional area of ​​the rotor. We can use thicker wires with low resistivity. Nowadays, of the rotor guide bars of small and medium-sized squirrel-cage motors are made of cast aluminum. If copper guide bars are used instead, the loss can be reduced by 10% to 15%.

2. Reduce stator copper loss

Because the electric power on the resistor W=I2R, reducing the resistance value and current can reduce the stator winding loss. The main methods are:

a. Expand the cross-sectional area of ​​the stator slot. Because this operation can reduce the area of ​​the magnetic circuit, thereby increasing the magnetic density of the teeth. b. Increase the filling rate of stator slots. c. Try to shorten the length of the stator winding end. It can be seen that reducing the winding end length can reduce the resistance value of the stator winding. Generally, the loss at the end of the stator winding accounts for 1/4 to 1/2 of the total winding loss. d. Develop earth permanent magnet synchronous motors. Eliminating the excitation winding and excitation current can not only simplify its structure, but also improve the working efficiency and power factor.

3. Reduce electronic iron losses

Methods to reduce the iron loss of permanent magnet motors include: a. Use cold-rolled silicon steel sheets. Choosing cold-rolled silicon steel sheets with magnetic permeability, stable quality, and relatively low loss can significantly reduce hysteresis losses. At the same time, the thickness of the silicon steel sheets can be easily reduced to reduce eddy current losses. b. Reduce the magnetic density. Reduce the density of magnetic flux by increasing the length of the core. c. Use iron chip insulating coating with performance. d. Use advanced heat treatment and manufacturing technology. After cold-rolled silicon steel sheets are processed by punching, shearing, bending, etc., mechanical stress and strain will occur, and the magnetism will change accordingly, resulting in an increase in iron loss. Therefore, it is necessary for us to heat treat it to restore its original magnetism, which can reduce the loss by 10% to 20%. At the same time, the development of new cold-rolled silicon steel sheets should be accelerated so that the iron loss does not change much after being processed into iron cores.

4. Reduce stray losses of permanent magnet motors

The stray losses of permanent magnet motors are mainly high-frequency losses caused by high-order harmonics of the magnetic field in the stator and rotor windings and iron cores. Generally accounts for 0.5% to 3% of the input power. The main methods to reduce stray losses are: a. Improve the design of the stator winding and reduce harmonics. b. Improve the cutting processing method of the outer surface of the rotor and the insulation treatment of the inner surface of the rotor slot. c. Use magnetic slot mud or magnetic slot wedges to replace traditional insulating slot wedges to weaken the cogging effect and thereby reduce additional stray losses accordingly.

5. Reduce ventilation friction loss

Because the high-efficiency motor adopts measures such as selecting high-quality materials and optimizing the 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, and we can choose axial flow or backward-inclined fans. In addition, we can also use higher quality bearings.