1. The coil current density should not be too large or too small: the motor coil has a certain resistance. When the current passes through the coil, loss occurs. The winding temperature increases, and the motor design hopes to reduce the resistance to reduce losses and improve efficiency. Bold Wire diameter, reducing the current density can reduce the resistance, but it will increase the amount of coil material. Due to the increase in the slot area, the core magnetic density increases, which increases the excitation current and iron loss of the motor. Usually the induction motor j is 3~7A/mm² (The large slot area means the core slot hole is large during chip design)2. The magnetic flux density of the motor core should not be too high or too low. When the core material, frequency and silicon steel sheet thickness are constant, the iron loss is determined by the magnetic flux density Ø. If the magnetic flux density is too high, the iron loss will increase and the motor efficiency will decrease. , the heating of the iron core increases the temperature rise of the motor. And because the excitation ampere-turn increases, the power factor of the motor decreases, so the magnetic flux density of the iron core should not be too high. Try to avoid using it in the supersaturated section of the magnetization curve. If the magnetic density is too low, the amount of motor material used will increase. Increase, the cost increases. The chip teeth are narrow, the magnetic density is high, that is, the slot space for the wire is large, and the core slot hole is large, and vice versa. 3. The motor slot fill rate should not be too high or too low. Generally, the slot fill rate is 75~85%. When the motor is running, the wires loosen in the slot, which can easily damage the insulation. In addition, there are many gaps in the slot, and due to poor thermal conductivity of the air, the coil will be affected. Heat dissipation increases the temperature rise of the motor.4. When designing the groove shape of the motor, try to use trapezoidal grooves with parallel teeth and avoid sharp corners on the edges of the grooves. Try to use round bottom grooves because the round grooves are well filled when aluminum is cast and are easy to make molds. The stator chip is easy to embed wires.5. The width of the motor slot should not be too large. If the slot is too large, the air gap flux will be unevenly distributed, and the tooth harmonics will increase. Additional losses will increase. It is usually about 3.5mm. If it is too small, it will be difficult to enter the wire.6. The number of stator slots should not be too many or too small. The asynchronous motor has a large number of stator slots, good magnetic potential and potential waveforms, small additional losses, and high motor efficiency. The large number of slots also increases the contact area between the coil and the iron core, and the coil heat dissipation is good. Low temperature rise. Good performance but difficult production process. High cost7. The asynchronous motor has a large air gap, large reluctance, and large excitation ampere-turns, which increases the motor excitation current and reduces the motor power factor. However, the air gap weakens the harmonic magnetic field and reduces the additional loss of the motor. If the air gap is too small, it is easy to cause The stator and rotor are swept, and the motor efficiency is reduced due to the increase in additional losses.8. The skew of the asynchronous motor rotor can weaken the harmonic potential phase of the rotor bar along the axial direction, thereby reducing the additional synchronous torque and additional asynchronous torque, reducing the additional loss of the motor, improving efficiency, and reducing noise. vibration.9. Do not use single-layer winding for motors with larger capacity, and do not use double-layer winding for motors with smaller capacity.10 Large motors should not use aluminum alloy as brackets because of poor stiffness and strength.11. Try to avoid using keyways of different widths (i.e. meson slots) on the rotating shaft. The second level of the shaft core should be rounded.12. When rolling bearings are used at both ends of the motor, do not get stuck in the axial direction. Because the heat dissipation of the rotating shaft is worse than that of the stator bracket when the motor is running, the temperature rises higher, and the thermal expansion of the rotating shaft is greater than that of the stator components, brackets, and base. The rotating shaft cannot Free expansion, so generally add wave meson and beer cap.13. The length of the rotating shaft and the rotor chip should not be too long. (The middle part of the shaft core can be reduced to solve the problem)14. Do not cause the motor rotor to move axially if it has a rolling bearing structure. (So the wave meson is added in the beer ring.) The sliding bearing has curved mesons on the front end of the rotor. The portable vacuum cleaner without curved mesons has a virtual E meson structure at the front end. Bit control is very small 0.1~0.4mm15. The stator and rotor cores of the motor should not be misaligned. Reasons for unfavorable misalignment a: misalignment is equivalent to reducing the effective area of the air gap, increasing the excitation current, and reducing the power factor. It also causes large stator current, large stator copper loss, and low efficiency. The temperature rises. B: The rotor is subjected to an axial force, which accelerates bearing wear and increases the noise and vibration of the motor. (However, some finished products often grind one end of the bearing in the forward direction and deliberately dislocate it.) c: Affect the normal ventilation of the motor.16. Pay attention to the quality of the asynchronous motor rotor cast aluminum (you can use sulfuric acid to dissolve the chip to check)17. The lead wire should not be too thin. If the lead wire is too thin, it is easy for the insulation to age. Usually, the current density of the conductor is 4~6A/mm², whichever is larger for small motors, and smaller for large motors.18. The starting current of the motor is generally about 6 times the rated current, so do not start it frequently. The locked-rotor current is usually 2.5 to 3 times the rated current. It takes 200% of the current to break the motor.19. The critical speed of the rotor should be greater than 1.2 times or less than 0.8 times the rated speed to avoid resonance.20. When drying the motor, avoid a sharp rise in temperature. Avoid using current to dry windings that are too wet.21. The stator slot wedge should not be higher than the inner circle of the iron core22. When disassembling the bearing and inserting the bearing, force should be applied to the inner ring and not to the outer ring and steel ball position.23. Do not use protected motors in dusty places and use enclosed motors. (But enclosed motors are not easy to dissipate heat.24. Do not run the motor at a power supply frequency that is too low. When the power supply voltage is constant, the frequency decreases and the magnetic flux increases. The motor design generally makes the silicon steel sheet work in the saturation zone of the magnetization curve. The increase in magnetic flux causes the excitation current to increase more, and the power factor Decrease, the motor current increases, the copper loss increases, the efficiency decreases, the frequency decreases and the motor speed decreases. The air volume decreases, heat dissipation is difficult, and the motor temperature rise increases. The decrease in power frequency not only decreases the motor output power, but also worsens various performances. Rated Frequency cannot exceed 1%25. Do not make the power supply voltage of the asynchronous motor too high or too low. The magnetic flux of the motor will decrease, and the motor torque will decrease in proportion to the square of the voltage. This will cause difficulty in electric starting. When the motor load remains unchanged, the motor current will increase and the loss will increase. , the temperature rise increases, and long-term low-voltage operation may cause the motor to burn out.26. The friction noise between the commutator and the carbon brush is caused by a. The surface processing accuracy of the commutator is insufficient and the roughness is poor. b. The gap between the carbon brush and the brush box is too large. c. The elastic force of the carbon brush spring fails. In addition, the commutator Debris on the surface can easily produce sparks.
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