Induction motor refers to a motor that uses electromagnetic induction between the stator and the rotor to induce current in the rotor to achieve electromechanical energy conversion. The stator of an induction motor consists of three parts: a stator core, a stator winding and a frame.
The rotor is composed of a rotor core, a rotor winding and a rotating shaft. The rotor core is also a part of the main magnetic circuit. It is generally made of silicon steel sheets with a thickness of 0.5mm. The core is fixed on the shaft or the rotor support. The appearance of the entire rotor is cylindrical. Rotor windings are divided into two types: cage type and winding type.
Under normal circumstances, the rotor speed of an induction motor is always slightly lower or slightly higher than the speed of the rotating magnetic field (synchronous speed), so the induction motor is also called "asynchronous motor".
When the load of the induction motor changes, the rotor speed and slip will change accordingly, so that the electromotive force, current and electromagnetic torque in the rotor conductor will change accordingly to meet the needs of the load. According to the positive, negative and magnitude of slip, induction motors have three operating states: motor, generator and electromagnetic brake.
The stator of an induction motor consists of three parts: a stator core, a stator winding and a frame. The stator core is part of the main magnetic circuit. In order to reduce the eddy current and hysteresis loss caused by the exciting current and the rotating magnetic field in the iron core, the iron core is made of silicon steel sheets with a thickness of 0.5mm. For motors with larger capacity, silicon steel sheets are coated with insulating paint on both sides for inter-chip insulation. The small stator core is laminated and compressed into a whole with silicon steel sheets and fixed in the frame; the medium and large stator cores are assembled by fan-shaped punching pieces. In the inner circle of the stator core, many slots of the same shape are uniformly punched. To embed the stator windings. Small induction motors usually use semi-closed slots and single-layer (discrete) windings wound by high-strength enameled wire, and there is a slot insulation between the coil and the iron core. The semi-closed slot can reduce the magnetic resistance of the main magnetic circuit and reduce the excitation current, but it is inconvenient to embed the wire. Medium-sized induction motors usually use half-open slots. Large-scale high-voltage induction motors all use open slots. To facilitate embedding. In order to obtain better electromagnetic performance, medium and large induction motors use double-layer short-pitch windings.
