All kinds of motors are widely used in the AC asynchronous motor (also known as induction motor).It is easy to use, reliable operation, low price, firm structure, but the power factor is lower, speed regulation is more difficult.Synchronous motors are commonly used in power machines with large capacity and low speed (see Synchronous motors).Synchronous motor not only has a high power factor, but also its speed has nothing to do with the size of the load and is only determined by the grid frequency.Work is more stable.In the requirements of a wide range of speed control occasions, the use of DC motor.But it has commutator, complex structure, expensive, difficult to maintain, not suitable for harsh environment.Since the 1970s, with the development of power electronics technology, the speed regulation technology of AC motor has gradually become mature, and the equipment price has been reduced day by day, and has been applied.The larger output mechanical power that the motor can bear under the specified working system (continuous type, short-time operation system, intermittent cycle operation system) without causing the motor to overheat is called its rated power. Attention should be paid to the provisions on the nameplate when using.When the motor is running, attention should be paid to matching the characteristics of its load with the characteristics of the motor to avoid flying or stopping.The range of power available from the milliwatt level to the megawatt level is very large.The use and control of the motor is very convenient, with self-starting, acceleration, braking, reverse, stop and other capabilities.Generally, the output power of the motor will change with the speed of speed.