具有梯形反电动势的永磁同步电动机通常被称为无刷直流电动机，它具有结构简单、体积小、重量轻、效率高、高功率密度、启动扭矩大、惯量小和响应快等其它种类直流电机无法比拟的特性。采用电子换向器替代了传统直流电动机的机械换向装置，从而克服了电刷和换向器所引起的噪声、火花、电磁干扰、寿命短等一系列弊病。-With a trapezoidal back-EMF permanent magnet synchronous motor is often referred to as brushless DC motor, it has a simple structure, small size, light weight, high efficiency, high power density, starting torque, inertia, and other types of fast response dc can not match the characteristics of the motor. Electronic commutator DC motor instead of the traditional mechanical reversing device, thereby overcoming the brushes and commutator caused by noise, sparks, electromagnetic interference, short life and a series of ills.