Working principle of single phase motor

Single-phase asynchronous motors generally consist of a stator, stator windings, rotor, rotor windings, starting device and end cover. Its basic structure is similar to that of three-phase asynchronous motors. Generally, a cage rotor is used, but the stator winding is different, generally only There are two sets of windings, one is called the main winding (also called the working winding or running winding), and the other is called the auxiliary winding (also called the starting winding or auxiliary winding). When a single-phase power supply is connected to the main winding, a magnetic field will be generated, but the position of this magnetic field in space will not change. The size and direction of the generated magnetic field are like sinusoidal alternating current. It is a pulsating magnetic field that changes periodically according to sinusoidal rules over time. The magnetic field can be considered as the synthesis of two rotating magnetic fields with equal rotation speed and opposite rotation direction. Therefore, two electromagnetic torques of the same magnitude and opposite directions are generated on the rotor, and the resultant torque is equal to zero, so the rotor cannot start on its own.

In order to enable the motor to start automatically, generally the main winding and the auxiliary winding have a spatial electrical angle difference of 90° in the stator, and the two sets of windings are connected to alternating current with a phase difference of 90° through the starting device, so that the two sets of windings The current has a phase difference in time. The starting winding current is 90° ahead of the working winding current. When the two currents pass into the two windings that are 90° apart in space, a rotating magnetic field effect will be formed. The role of the cage rotor in the rotating magnetic field Under the condition, a starting torque is generated and the rotation starts by itself at a speed lower than that of the rotating magnetic field.

Post time: Jan-10-2024