Losses and reduction measures of high-efficiency and energy-saving motors

We have introduced the inspection of high-efficiency and energy-saving motors before starting. It can be seen that before starting this equipment, inspections must be done to avoid unnecessary accidents. However, high-efficiency and energy-saving motors will inevitably produce some losses during their operation. So what are the losses and how to reduce them? Next, the editor will discuss these issues in detail!

The losses and reduction measures of high-efficiency and energy-saving motors are as follows:

1. Stator loss

There are many ways to reduce the stator I^2R loss of high-efficiency and energy-saving motors, but the main methods used in practice are as follows:

(1) Increase the slot cross-sectional area of ​​the stator. Under the same stator outer diameter, increasing the stator slot cross-sectional area will reduce the area of ​​the magnetic circuit and increase the magnetic density of the teeth;

(2) Increase the stator slot full rate, which is better for low-voltage small motors. The application of winding and insulation dimensions and large conductor cross-sectional area can increase the stator slot full rate;

(3) Minimize the length of the end of the stator winding. The loss at the end of the stator winding accounts for 1/4 to 1/2 of the total loss of the winding. We can reduce the length of the end of the winding. This can improve the working efficiency of the high-efficiency and energy-saving motor. And experiments show that if the end length is reduced by 20%, the loss can be reduced by 10%.

2. Rotor loss

The I^2R loss of the motor rotor is mainly related to the rotor current and rotor resistance. The corresponding energy-saving methods mainly include the following:

(1) To reduce the rotor current, we can take two measures: increasing the voltage and motor power;

(2) Increase the cross-sectional area of ​​the rotor slot;

(3) Reduce the resistance of the rotor winding. For example, choose thick wires and materials with low resistance. This is more meaningful for small motors, because small motors generally have cast aluminum rotors. If a cast copper rotor is used, the total loss of the motor can be reduced. 10% to 15%. However, the current cast copper rotor requires high manufacturing temperatures and the technology has not yet been popularized. Its cost is 15% to 20% higher than that of cast aluminum rotors.

3. Iron consumption

The iron loss of high-efficiency and energy-saving motors can be reduced through the following measures:

(1) Reduce the magnetic density and increase the length of the iron core to reduce the magnetic flux density, but the amount of iron used in the motor will increase accordingly;

(2) Reduce the loss of induced current by reducing the thickness of the iron sheets. For example, using cold-rolled silicon steel sheets instead of hot-rolled silicon steel sheets can reduce the thickness of the silicon steel sheets, but thin iron sheets will increase the number of iron sheets and motor manufacturing cost;

(3) Use cold-rolled silicon steel sheets with good magnetic permeability to reduce hysteresis losses;

(4) Use high-performance iron chip insulation coating;

(5) Heat treatment and manufacturing technology. The residual stress after processing the iron sheet will seriously affect the loss of the motor. When processing silicon steel sheets, the cutting direction and punching shear stress have a greater impact on the loss of the iron core. We can cut the silicon steel sheets along the rolling direction and heat treat the silicon steel punched sheets, which can reduce the loss by 10% to 20%.

4. Stray losses

So far, our country’s understanding of motor stray losses is still in the research stage. The main methods to reduce stray losses currently include:

(1) Use heat treatment and finishing to reduce short circuits on the rotor surface;

(2) Insulation treatment on the inner surface of the rotor slot;

(3) Reduce harmonics by improving the stator winding design;

(4) Improve the rotor slot design and coordination to reduce harmonics, increase stator and rotor tooth slots, design the rotor slot shape into inclined slots, and use series-connected sinusoidal windings, scattered windings and short-distance windings to greatly reduce high-order harmonics. ; You can also use magnetic slot mud or magnetic slot wedges to replace the traditional insulating slot wedges. Use magnetic slot mud to fill the slots of the motor stator core, which is an effective method to reduce additional stray losses.

5. Friction loss

Friction loss accounts for about 25% of the total loss of high-efficiency and energy-saving motors. Friction losses are mainly caused by bearings and seals and can be reduced by the following measures:

(1) Reduce the size of the shaft as much as possible, but it must meet the requirements of output torque and rotor dynamics;

(2) Use high-efficiency bearings;

(3) Use efficient lubrication systems and lubricants;

(4) Adopt advanced sealing technology.