Working principle of three-phase asynchronous motor

The working principle of three-phase asynchronous motor is mainly based on the interaction of stator rotating magnetic field and rotor current. Here's a detailed explanation:

1. Generation of stator rotating magnetic field

When the stator winding of the motor passes through the three-phase AC current, the current in each phase winding will generate its own magnetic field. Because the three-phase currents are 120 degrees out of phase, the magnetic fields they generate are superimposed on each other in space, forming a rotating magnetic field. The direction and speed of this rotating magnetic field depend on the frequency of the current and the arrangement of the windings. ‌

2. Rotor induced potential and current generation

The rotor winding (whether cage or wound) is in the stator rotating magnetic field. Due to the relative motion between the rotor and the stator magnetic field, according to the principle of electromagnetic induction, the electromotive force will be induced in the rotor winding, and then the induced current will be generated. ‌ 23

3. Electromagnetic torque generation

The induced current in the rotor winding interacts with the stator's rotating magnetic field, which, according to the Left Hand rule (or Lorentz force law), creates an electromagnetic force that acts on the rotor, causing it to rotate in the direction of the rotating magnetic field. Because the rotor speed is always slightly lower than the speed of the rotating magnetic field (there is a slip rate), it is called an asynchronous motor. ‌

4. Energy conversion

In this process, electrical energy is converted into mechanical energy through electromagnetic induction and electromagnetic force, which drives the rotor of the motor to rotate, thus completing the work of the motor. ‌

5. Speed adjustment and start

For the winding three-phase asynchronous motor, the starting performance of the motor and the speed of the motor can be improved by adjusting the resistance of the external rheostat.

6. Visual understanding

The working principle of three-phase asynchronous motors can be more intuitively understood through 3D animation or experimental installations. For example, a model using a U-shaped magnet and a metal disk (or cylinder) simulates the generation of a rotating magnetic field and the movement of the rotor by changing the position of the magnet or the direction of the current. ‌

To sum up, the working principle of the three-phase asynchronous motor is a complex electromagnetic process, involving the generation of the stator rotating magnetic field, the generation of the rotor induced potential and current, the generation of electromagnetic torque and energy conversion. This process allows the motor to effectively convert electrical energy into mechanical energy, which drives the operation of various equipment and machinery.