Among all kinds of motors, the most widely used is AC asynchronous motor (also known as induction motor). It is convenient to use, reliable to run, low price, firm structure, but the power factor is low, speed regulation is also more difficult. 

Synchronous motors are commonly used in power machines with large capacity and low speed. Synchronous motor not only has a high power factor, but its speed is also independent of the load and only depends on the frequency of the grid. It works more stable. Dc motor is used in wide range of speed regulation. But it has a commutator, complex structure, expensive, difficult maintenance, not suitable for harsh environments. 

Since the 1970s, with the development of power electronics technology, the speed regulation technology of AC motor has become more and more mature, and the equipment price has been reduced day by day, and it has been applied. The maximum output mechanical power that the motor can bear under the prescribed working mode (continuous, short time operation system, intermittent cycle operation system) without causing the motor to overheat is called its rated power. 

Please pay attention to the stipulations on the nameplate when using. When the motor is running, the characteristics of its load should be matched with the characteristics of the motor to avoid flying or stopping. Electric motors provide a wide range of power, from the milliwatt level to the megawatt level. The use and control of the motor is very convenient, with self-starting, acceleration, braking, reversing, pawling and other capabilities. It can meets various operating requirements. 

The motor has higher working efficiency, no smoke, no smell, no pollution of the environment, and less noise. Because of a series of advantages, it is widely used in industrial and agricultural production, transportation, national defense, commerce and household appliances, medical appliances and other aspects. The output power of the general motor varies with the speed.