Precautions for designing brushless DC motors.
Although design is a necessary operation before producing DC brushless motors, we can produce according to the design requirements after design. However, due to the fact that the motor contains many precision parts and has high requirements in many aspects, we should pay attention to the following points when designing the motor:
1、 The main performance parameters to be considered during the redesign of ordinary motors in electromagnetic design are overload capacity, starting performance, efficiency, and power factor. Due to the inverse proportionality between the critical slip rate and the power frequency, when the critical slip rate approaches 1, the variable frequency motor can be started directly without considering excessive overload capacity and starting performance. However, the key issue to be solved is how to improve the adaptability of the non sinusoidal power source of the variable frequency motor. This method is generally as follows:
(1) Minimize the resistance of the stator and rotor as much as possible. Reducing stator resistance can reduce basic copper loss to compensate for the increase in copper loss caused by high-order harmonics.
(2) In order to prevent high-order harmonics in the current of brushless DC motors, it is necessary to appropriately increase the inductance of variable frequency motors. The size of the leakage reactance of the variable frequency motor should consider the rationality of impedance matching throughout the entire speed regulation range.
2、 In the structural design, the influence of non sinusoidal power supply characteristics on the insulation structure, vibration, and noise cooling methods of the variable frequency motor is also considered. Usually, the following issues should be noted:
(1) The insulation level, usually F or higher, can enhance the insulation strength and turns to ground, especially the ability to withstand insulation pulse voltage.
(2) For the vibration and noise of DC brushless motors, the rigidity of the variable frequency motor components and the overall structure should be fully considered, and the natural frequency should be increased as much as possible to avoid resonance with each force wave.
(3) Cooling method: Forced ventilation is used for cooling, that is, the cooling fan of the main motor is driven by an independent motor.
(4) Measures to prevent shaft current. Electric motors with a capacity exceeding 160KW should adopt bearing insulation measures. The main reason is that magnetic circuit asymmetry may occur, and shaft current may also occur. When the currents generated by other high-frequency components are combined, the shaft current will greatly increase, leading to bearing damage. Therefore, insulation measures are usually taken.
After learning about the precautions for designing a brushless DC motor, it is necessary to design the motor according to the design requirements. At the same time, you should also pay attention to the above listed precautions, as they are related to the normal use of the motor.
