Motor design rules (three)
17, the motor starting current is generally about 6 times the rated current, so do not start frequently, the locked current is usually 2.5 to 3 times the rated current. Current Phillips needs 200% of the current to break.
18, the lead should not be too thin. If the lead is too thin, it is easy to insulate. Generally, the conductor current density is 4~6A/mm2. The small motor takes a large value. The large motor takes a small value.
19. Friction noise of commutator and carbon brush. It is because the surface of a commutator is not accurate enough and the roughness is poor. b. The carbon brush and brush box gap is too large. c carbon brush spring elastic failure. In addition, commutator There are debris on the surface that is prone to sparks.
20, the rotor critical speed should be greater than 1.2 times or less than 0.8 times the rated speed to avoid resonance.
21. When the motor is dry, avoid the temperature rise sharply. Excessively wet windings should avoid drying with the method of passing current.
22, the stator wedge should not be higher than the core inner circle
23, disassemble the bearing into the bearing should be added to the inner ring of the beer, can not force the outer ring and steel ball.
24, multi-dust places do not use closed motor with protective motor. (But closed motor is not easy to dissipate heat.
25. Do not run the motor when the power supply frequency is too low. When the power supply voltage is constant, the frequency decreases to increase the magnetic flux. The motor design generally makes the silicon steel sheet work in the saturation region of the magnetization curve. The increase of the magnetic flux increases the excitation current, and the power factor Decrease, the motor current increases, the copper loss increases, the efficiency decreases, and the frequency decreases, the motor speed decreases. The air volume decreases, the heat dissipation is difficult, and the motor temperature rises. The power frequency decreases, not only the motor output power decreases, but also the performance deteriorates. Frequency cannot exceed 1%
26. Do not make the power supply voltage of the asynchronous motor too high or too low. The motor flux is reduced. The motor torque is proportional to the square of the voltage. It is difficult to start the electric motor. When the motor load is constant, the motor current increases and the loss increases. The temperature rise is increased, and the long-term low-voltage operation may cause the motor to burn out.
