1. Basic structure of synchronous motor
(1) Stator
The stator of synchronous motor is called armature, and the structure is the same as that of three-phase asynchronous motor, which is composed of stator core, stator winding, frame and end cover. The stator core is composed of silicon steel sheet, and the three phase symmetrical winding is embedded in the core groove.
(2) Rotor
The rotor consists of a rotor core, an exciting winding, a starting winding and a rotating shaft. The rotor core is made of cast or forged steel with an exciting winding around it. The excitation winding is connected to the excitation power supply and connected to the excitation current. The starting winding consists of a copper bar embedded on the surface of the magnetic pole, and the two ends of the copper bar are connected by copper rings, which is the same as the squirrel cage rotor of the asynchronous motor. The rotor of three-phase synchronous motor has two kinds: hidden pole type and convex pole type.
Non-salient pole type
The core of the hidden pole rotor is cylindrical, the surface is slotted, the field winding is embedded in the groove, and the air gap between the stator core and the stator core is relatively uniform.
Salient pole type
The field winding of the salient pole rotor is concentrated on the core column between the two magnetic poles, and the atmosphere between the stator core is uneven.
2. The basic principle of synchronous motor
1) The three-phase AC power supply is added to the stator winding, and the three-phase symmetrical alternating current is passed into the stator winding to generate a rotating magnetic field with a rotating speed of n0; Dc current is passed into the rotor field winding to generate a stationary magnetic field with constant polarity.
2) After the rotor is started in a certain way, when the speed n is close to n0, if the logarithm of the magnetic pole of the rotor magnetic field is equal to the logarithm of the stator magnetic field, according to the principle of magnetic pole attraction, the magnetic pole between the fixed and rotor magnetic field will tend to align. When the synchronous motor is actually running, due to the existence of resistance, the magnetic pole axis of the rotor always lags behind the rotating magnetic field axis by an Angle 0. A magnetic pull of the opposite sex is generated, that is, electromagnetic torque, which causes the rotor to move synchronously with the rotating magnetic field, that is, n=n0. This is the basic principle of synchronous motors.
