Publish Time: 2023-11-04 Origin: Site
The working principle of an induction motor is as follows. When the three-phase stator windings pass through three-phase symmetrical alternating current, a rotating magnetic field is generated. This rotating magnetic field rotates in the inner bore of the stator, and its magnetic field lines cut the wires on the rotor and induce induction in the rotor wires. current. Due to the interaction of the stator magnetic field and the rotor current to generate electromagnetic torque, the stator rotating magnetic field drags the rotor to rotate through the current-carrying wire.
Here is the list
The basic structure of an induction motor
Induction Motor Air Gap Rotating Magnetic Field and Induced Electromotive Force
Exciting electromotive force of induction motor
Like other types of motors, an induction motor consists of three parts: a stationary part, a rotating part, and an auxiliary part. Induction motors are mainly composed of stators, rotors and auxiliary components. The stator includes a wound stator iron core and a frame; the rotor includes a cast aluminum rotor, a rotating shaft and a balance block, etc.; the auxiliary parts include an end cover, a junction box, a fan and a hood. Induction motors include squirrel cage induction motors and wound induction motors
When the induction motor is working, the basic magnetic field of the air gap established by the stator and the rotor interacts with the current of the rotor winding to generate an electromagnetic force (Fe) and form an electromagnetic torque. The electromagnetic torque overcomes the load torque and outputs mechanical work, and the induction motor realizes electromechanical energy conversion. The normal operation of an induction motor must meet two basic conditions: the fundamental magnetomotive force of the stator and rotor of the motor must be able to synthesize in the air gap and establish a rotating magnetic field; the rotor speed must be less than the speed of the air gap magnetic field, and the difference between the two must be maintained. The air-gap fundamental wave rotating magnetic field is also the rotation speed of the main magnetic field, and its relationship with the power supply frequency is: ns=60f/p where ns——synchronous speed (r/min); f——stator power supply frequency (Hz) ; p - the number of pole pairs in the stator winding. It should be pointed out that the no-load air-gap magnetic field of the induction motor is established by the alternating magnetomotive force of the stator windings.
Exciting electromotive force: When a symmetrical three-phase alternating current is applied to an asynchronous motor, a rotating air gap magnetic field is generated in the air gap. This rotating magnetic field will cut the stator and rotor windings at the same time, causing the two windings to generate corresponding induced electromotive forces, but since the rotor windings are open, there is no current, that is, no magnetomotive force.
It can be seen that in this case the entire air-gap magnetic field is generated by three-phase symmetrical currents in the stator windings. For this reason, the stator magnetomotive force is also called the excitation magnetomotive force, and the stator current is also called the excitation current. Since the whole analysis process is completely symmetrical, only one phase (A phase) is used as an example in the analysis. The magnetomotive force characteristics of the rotating magnetic field generated by the current: when the phase A current reaches a positive maximum, the corresponding magnetomotive force also reaches a positive maximum. A three-phase asynchronous motor whose rotor does not rotate is equivalent to a three-phase transformer with an open circuit on the secondary side. The stator winding is the primary winding, and the rotor winding is the secondary winding, but in the magnetic circuit, there is an extra iron core in the stator and rotor of the asynchronous motor. Air gap magnetic circuit only.
Main magnetic field: When a three-phase symmetrical voltage is applied to the three-phase winding of the stator, a three-phase symmetrical current flows through the winding to generate a rotating magnetomotive force and establish a rotating magnetic field. Among them, the basic magnetic field that reaches the rotor through the air gap plays a major role, which is called the main magnetic field.
Hangzhou New Hengli Electric Machine MFG. Co., Ltd. works has been named the provincial advanced enterprise by Zhejiang provincial government and become a state grade-2 enterprise in 1988. Our motor max-power reaches 15000kW (A.C. motor), 2800kW (D.C. motor), and max-center-high dimension of our motor reaches 1250mm.