A three-phase asynchronous motor is a type of motor that relies on the simultaneous connection of a 380V three-phase AC power supply. Due to the fact that the rotor and stator rotating magnetic fields of a three-phase asynchronous motor rotate in the same direction but at different speeds, there is a slip rate, so it is called a three-phase asynchronous motor.
The three-phase asynchronous motor is an electrical equipment that realizes the mutual conversion of electrical energy and mechanical energy. The motor uses the principle of electromagnetic induction to achieve the mutual conversion of electrical energy and mechanical energy. The equipment that converts mechanical energy into electrical energy is called a generator, while the equipment that converts electrical energy into mechanical energy is called an electric motor.
In fact, three-phase asynchronous motors generate induced current and electromagnetic torque on the rotor through the rotating magnetic field of the stator. The speed of the motor rotor must be lower than the synchronous speed, because the motor rotor does not directly generate a magnetic field. When the symmetrical three-phase winding of the stator is connected to the three-phase power source, a symmetrical three-phase current will be introduced into the winding and a rotating magnetic field will be generated in space. The magnetic field rotates along the circumferential direction inside the stator. When the magnetic field rotates, the conductor of the rotor winding will cut the magnetic flux and generate an induced electromotive force E. Due to the existence of electromotive force E, the rotor current I will be generated in the rotor winding. According to Ampere's electromagnetic force law, the rotor current is the same as the direction of rotation, and the rotor will rotate in the direction of the rotating magnetic field due to this torque. However, the rotation speed n of the rotor is constant. The rotation speed n0 is smaller than that of a rotating magnetic field, Because if the two speeds are equal, there is no relative motion between the rotor and the rotating magnetic field, and the rotor conductor does not cut the magnetic flux, it cannot generate induced electromotive force and current, and there is no electromagnetic torque. The rotor will not continue to rotate. Therefore, the speed difference between the rotor and the rotating magnetic field is the main factor to ensure the rotation of the rotor. This is the working principle of a three-phase motor, so it is called an asynchronous motor.
Three phase motors are still very convenient for certain fields. Asynchronous motors have strong overload capacity, are sturdy and durable, and are fully compatible with them. In addition, the basic control circuit of three-phase asynchronous motors is widely used in daily life and production. For example, the starting process of lifting equipment has a large current, but after starting, the current will drop to the rated value. Therefore, in the starting control circuit of heavy-duty equipment, current transformers and intermediate relays are used to control the starting of heavy-duty equipment, or current relays are used to complete the starting of heavy-duty equipment.
Three phase asynchronous motors are widely used in production due to their simple layout, stable operation, durability, low cost, and easy maintenance. They are also widely used to drive various metal cutting machine tools, conveyor belts, cranes, forging machines, casting machinery, ventilation fans and water pumps with low power output.