AC motors - explanation

DESCRIPTION

AC motor is used to achieve mechanical energy conversion and AC power machinery. Due to the huge development of power systems AC, AC motor has become the most commonly used motors. AC motor compared with DC motors, because there is no commutator structure is simple, easy to manufacture, relatively strong, easy to make high-speed, high-voltage, high-current, high-capacity motor. Coverage AC motor power is great. AC motors are usually divided according to their function alternators, AC motors and synchronous condenser categories. Because of the reversibility of the motor operating state, the same motor can be made not only for the generator motor. The motor into a generator and the motor is not very accurate, but some main motor as a generator to run some motors mainly for the motor is running.

Text

Achieve mechanical energy conversion and AC power machinery. Due to the huge development of power systems AC, AC motor has become the most commonly used motors. AC motor compared with DC motors, because there is no commutator (see DC motor commutation), the structure is simple, easy to manufacture, relatively strong, easy to make high-speed, high-voltage, high-current, high-capacity motor. Coverage AC motor power widely, from a few watts to hundreds of thousands of kilowatts, or even millions of kilowatts. The early 1980s, the largest turbine generator has reached 1.5 million kilowatts.

AC motors are usually divided according to their functions alternators, AC motors and synchronous condenser categories. Because of the reversibility of the motor operating state (see motor), the same motor can be made not only for the generator motor. The motor into a generator and the motor is not very accurate, but some main motor as a generator to run some motors mainly for the motor is running.

AC motors by species divided synchronous motors, asynchronous motors into two categories. Ns with the same rotation speed of the rotating magnetic field synchronous motor rotor speed, called synchronous speed. ns and the connected alternating current frequency (f), between the number of motor poles (P) of a strict relationship

ns = f / P in China, the power frequency is 50 Hz, so the two-pole synchronous motor speed of 3000 rev / min, four-pole motor synchronous speed of 1500 rev / min, more than analogy. Induction motor rotor speed is always lower or higher than the rotating magnetic field, the name of the resulting asynchronous. Poor induction motor rotor speed and the speed of the rotating magnetic field (called slip) is usually less than 10%. From this, the AC motor (either synchronous or asynchronous) are subject to the speed of power frequency constraints. Thus, AC motor speed control is more difficult, the best way is to change the frequency of the power, but in the past to change the power frequency is more complex. So 70 years ago, asking the governor of the occasion, the use of DC motors. With the development of power electronics technology, frequency conversion technology has begun to get the AC motor practical.

Generally use a three-phase AC motor system, as compared to the three-phase AC motor with single-phase motors, both in terms of performance, utilization and price of raw materials has obvious advantages. The same power three-phase motor size smaller than the single-phase motor, light weight, low price. Three-phase motor with self-starting. Single-phase motor is not starting torque, start to solve the problem, we need to take some special measures (see the single-phase induction motor). Single-phase motor torque is pulsating, the noise is relatively large, but the required power is relatively simple, especially for use in the home is very convenient. So small household electrical and instrument motor multi-use single-phase motor.