Brushless DC motors are widely used in electric vehicles because they have the following two advantages over conventional brushed DC motors.
(1) Long life, maintenance-free, and high reliability. In the brushed DC motor, the brush and the commutator wear faster because of the higher motor speed, and the brush needs to be replaced after about 1000 hours of work. In addition, the technical difficulty of the reduction gear box is relatively large, especially the lubrication problem of the transmission gear, which is a relatively large problem in the current brush scheme. Therefore, there are problems such as large noise, low efficiency, and easy failure. Therefore, the advantages of brushless DC motors are obvious.
(2) High efficiency and energy saving. In general, because brushless DC motors have no mechanical commutation friction loss and gearbox consumption, as well as speed control circuit losses, the efficiency is usually higher than 85%, but in view of the most cost-effective design in the actual design, to reduce material consumption. The general design is 76%. The efficiency of brushed DC motors is typically around 70% due to the consumption of gearboxes and overrunning clutches.