The difference between dc motor and ac motor.

According to the power type, the motor can be divided into dc motor and ac motor. In this period, the motor will introduce the dc motor and ac motor and the difference between the two.

Dc motor is the motor that can convert the dc motor and the mechanical energy, when the mechanical energy can be converted into electrical energy. The working principle of dc generator alternating emf is induced in the armature coils, the commutator with brush commutation function, make it from the brush end into the principle of dc electromotive force.

Working principle of dc motor.

Fixed inside a circular permanent magnet dc motor, the current through the coil produces ampere force on the rotor, when the rotor coil and magnetic fields on the parallel, turn again by the magnetic field direction will change, so the rotor at the end of the brush to convert alternating contact, thus the direction of the electric current on the coil change, loren magnetic direction remains the same, so the motor can keep a direction.

The working principle of dc generator alternating emf is induced in the armature coils, the commutator with brush commutation function, make it from the brush end into the principle of dc electromotive force.

The direction of the induced electromotive force is determined by the right hand rule (the magnetic sense line points to the palm, the thumb points to the direction of the conductor, and the other four points are the direction of the inductive electromotive force in the conductor).

The direction of the force of the conductor is determined by the left hand rule. This pair of electromagnetic force formed on the armature a torque, the torque in rotary motor is called electromagnetic torque, torque direction is counterclockwise, trying to make the armature counterclockwise rotation. If this electromagnetic torque can overcome the torque on the armature (such as the resistance torque caused by friction and other load torque), the armature can be rotated counterclockwise.

Ac motor:

Ac motor is a machine used to realize mechanical energy and alternating current. Due to the tremendous development of ac power system, ac motor has become a common motor. Compared with dc motor, the ac motor is simple in structure, convenient in manufacturing and easy to be made into high speed, high voltage, large current and large capacity. Ac motor power covers a wide range from a few watts to hundreds of thousands of watts, or even millions of watts.

Differences between dc motor and ac motor:

1. The motor whose speed is proportional to the voltage is the dc motor, and the motor with a direct ratio of speed and frequency is called ac motor.

2. The dc motor is commutating by coil, and the ac motor is a step by step group.

3. The dc motor is regulated speed regulation, while ac motor is variable frequency speed regulation, which is the watershed of dc motor and ac motor.

4. The fundamental difference between dc motor and ac motor is that the electric potential balance equation is different:

1) the electric potential balance equation of the dc motor is: U=C.

2) the electric potential balance equation of ac motor is: U=C.

3) dc motor with rapid response, large starting torque, rotating speed of from zero to rated speed can provide the performance of the torque, but the advantages of dc motor is also its drawback, because the direct current machine to produce a constant torque under rated load, the performance of the armature magnetic field and rotor magnetic field should be maintain 90 ˚ constant, which is inspired by carbon brush and commutator motor rotation would produce sparks, carbon powder, so in addition to cause damage of components, its usage is restricted. The ac motor has no carbon brush and commutator, is free of maintenance, rugged and widely used. However, it is necessary to use complex control technology to achieve the performance of the dc motor. The three-phase asynchronous motor has simple structure, reliable operation and low cost.