Difference: ac motor and dc motor driving power source is different, the kinds of ac motor is ac, dc motor is dc. Ac motor is formed by the stator rotating magnetic field on the rotor induction electric potential after produce the rotation of power. Speed is usually fixed rotational speed. Small to household refrigerator washing machine cleaner, big to machine tool, etc. , are using ac motor. Dc motor stator is a fixed magnetic field, a direct current through the rotor's brush form changing magnetic field around it, thus in the stator internal rotation. In industrial enterprises, the dc power supply is relatively reliable, reliable operation of dc motor is generally used in requirements spare machinery or security; As the input voltage changes due to dc motor speed can also change, so need to often speed used dc motor is also many, such as milling machine, planer, electric cars, metro trains, and so on. Because communication is easy to get, easy to transport, so we currently include the use of electric machinery parts are ac motor driver, ac motor used more widely. Brushless dc motor, the stator is a rotating magnetic field, dragging the rotor magnetic field rotation. Ac synchronous motor, stator rotating magnetic field is also dragged the rotor rotating magnetic field. Stepper motor and ac servo motor performance comparison: stepping motor is a kind of discrete movement of the device, it has the nature of the contact and the modern digital control technology. In the current domestic digital control system, stepping motor is widely used. With the emergence of digital ac servo system, ac servo motors are increasingly used in the digital control system. In order to adapt to the development trend of digital control, motion control systems mostly adopt stepper motor or all-digital ac servo motor as the executive motor. Although both similar on control mode (Pulse sequence and direction signal), but in the use of performance and applications on there is a big difference. A comparison to be made regarding the use performance of both. The notion of a asynchronous motor and synchronous motor and the difference between: synchronous motor on excitation current, without excitation, is asynchronous motor. Synchronous motor on excitation current, without excitation, is asynchronous motor. Excitation is added on the rotor dc system, its rotation speed and polarity and the stator is consistent, if the excitation appear problem, step motor will lose, not to be able to adjust, trigger protection field fault motor tripping, said the white point of field current is the flow of electric current in a synchronous motor rotor (With this current, make the rotor is equivalent to an electromagnet, a N pole and S pole)During normal operation, the current is produced by the external on the dc voltage on the rotor. Before this dc voltage is supplied by dc motor, now mostly by controllable silicon rectifying after supply. We usually called the silicon controlled rectifier system excitation device. The asynchronous machine is motor rotation speed and the stator rotating magnetic field generated by the rotation speed is not consistent, there is a difference (Out of sync)。 We call slip. The slip and the speed of the stator rotating magnetic field generated by the ratio of the call slip. The difference between synchronous and asynchronous machine: asynchronous machine is only in the stator voltage synchronous and asynchronous machine with the difference between said, from the aspects of power supply,Have applied voltage on the rotor), and synchronous confidential and voltage on the stator and rotor. Step that is different machine is unilateral excitation, synchronous machine is bilateral excitation. Said from the aspects of speed, the speed of the asynchronous machine is only related to the load size (Of course there are certain range),, and rotational speed of the synchronous machine is only related to the frequency of the power grid. Say from structure, synchronous motor and asynchronous machine rotor structure is different also. Asynchronous machine rotor is evening article sheet steel and aluminumOr evening of steel sheet and coil), and synchronous machine generally consists of several piece of magnet steel and coil (There is also a non-salient pole type are not quite same)Of course there are many differences, such as technical requirements, design issues and so on. Synchronization refers to the frequency of the alternating current synchronous speed and motor power, and has nothing to do with the load of the motor asynchronous refers to the speed of the motor and the frequency of the alternating current power supply are not synchronized, associated with the load of the motor. Points, from the application of synchronous motor used in strict with rotational speed, the price also is very expensive. Asynchronous motor is widely used in general situation, price is low.
