The working principle of AC motor!
The single-phase AC motor has only one winding, and the rotor is squirrel cage. When a single-phase sinusoidal current through the stator windings, the motor generates an alternating magnetic field, the magnetic field strength and direction for sinusoidal variation with time, but the spatial position is fixed, so it is also called the magnetic field is alternating pulsating magnetic field. The alternating pulsating magnetic field can be divided into two with the same speed, the rotation direction of the rotating magnetic field are on the contrary, when the rotor is at rest, the two rotating magnetic field generating torque of two equal and opposite in the rotor, the synthetic torque is zero, so the motor rotation. When we use a force of the motor rotation to one direction (e.g., clockwise), the rotor and the clockwise rotation direction of the rotating magnetic field between the motion of cutting magnetic lines becomes smaller; the rotor and the counterclockwise rotation direction of the rotating magnetic field between the motion of cutting magnetic lines becomes large. Thus, the balance is broken, and the total electromagnetic torque generated by the rotor will no longer be zero, and the rotor will rotate in the direction of the push.
The prerequisite of the three-phase asynchronous motor to rotate is to have a rotating magnetic field, and the stator winding of the three-phase asynchronous motor is used to generate a rotating magnetic field. As we know, but the voltage phase power phase between the difference of 120 degrees in phase three, a stator winding of the three-phase induction motor in the spatial direction is 120 degrees, so when in the stator windings in three-phase power, the stator winding will produce a rotating magnetic field, as shown in Figure 1 in the process of its generation. The graph is divided into four moments to describe the generation of the rotating magnetic field. In each period of the current, the rotating magnetic field rotates in space for a week, i.e., the rotation speed of the rotating magnetic field is synchronous with the change of the current. The rotation speed of rotating magnetic field is: n=60f/P, f is power frequency, P is magnetic pole, logarithm and N unit is: revolutions per minute. According to this formula, we know that the speed of the motor is related to the number of poles and the frequency of the power supply. To this end, there are two ways to control the speed of the alternating current motor: 1, change the magnetic pole method; 2, frequency conversion method. In the past, the first method was used, and now the variable speed control of AC motor is realized by frequency conversion technology.
At present, there are two kinds of AC motors commonly used: 1 and three-phase asynchronous motors. 2 、 single-phase AC motor. The first type is widely used in industry, while the second is used in civil electric appliances.
