The general brushless dc motor is essentially a servo motor, which is made up of synchronous motor and driver. The brushless dc motor is a real brushless dc motor. It is composed of a stator and a rotor. The stator is made of a core. The rotor is composed of a cylindrical magnet (middle band shaft) or an electromagnet with a collector ring. This brushless dc motor can generate torque, but it cannot control direction. In any case, this motor is a very significant invention. When it used as a dc generator, the invention can generate continuous dc current with continuous amplitude, thus avoiding the use of filter capacitors. The rotor can be permanent, brush or brushless. When it is a large motor, this electric opportunity produces self-induction and need to use protection device.