The ubiquitous induction motor silently provides power for our lives and production. What kind of magical working mechanism does it have? Today, let us walk into the world of induction motor and explore the working principle behind it.
Open the mysterious door of electromagnetic induction
Before understanding the working principle of induction motor, we need to understand the phenomenon of electromagnetic induction. In 1831, British physicist Faraday discovered that a changing magnetic field can generate an electric field, which in turn generates a current, which is called an induced current. This great discovery laid a solid theoretical foundation for the invention of the motor, and the induction motor is a device that cleverly uses the principle of electromagnetic induction to achieve energy conversion.
The basic structure of the induction motor
The induction motor is mainly composed of two parts: the stator and the rotor. They cooperate with each other to complete the conversion of electrical energy to mechanical energy.
(I) Stator
The stator is equivalent to the “shell” of the motor. It is mainly composed of a stator core, a stator winding and a frame. The stator core is made of mutually insulated silicon steel sheets. The stator winding is wound by insulated wire and embedded in the slot of the stator core according to a certain rule. The main function of the machine base is to support and fix the stator core to ensure the structural stability of the motor.
(II) Rotor
The rotor is the rotating part of the induction motor and is the key component of the motor output mechanical energy. It can be divided into squirrel cage rotor and wound rotor.
Working process of induction motor
(I) Generation of rotating magnetic field
When three-phase alternating current is passed into the stator winding, a rotating magnetic field will be generated in the internal space of the stator due to the phase difference between the three-phase current in time and space.
(II) Generation of rotor induced current
The rotating magnetic field rotates continuously in space, and the rotor conductor moves in a cutting magnetic flux line relative to the rotating magnetic field. According to the principle of electromagnetic induction, an induced electromotive force will be generated in the rotor conductor. Since the rotor winding is a closed loop, an induced current will be generated in the rotor conductor under the action of the induced electromotive force.
(III) Generation of electromagnetic force and rotor rotation
According to Ampere’s law, a current-carrying conductor will be acted upon by a force in a magnetic field. The induced current in the rotor conductor is acted upon by electromagnetic forces in the rotating magnetic field. These electromagnetic forces form electromagnetic torque on the rotating shaft, driving the rotor to rotate in the direction of the rotating magnetic field. The speed of the rotor is always slightly lower than the speed of the rotating magnetic field. There is a speed difference between the two, which is called the slip rate. It is precisely because of the existence of the slip rate that the rotor conductor can continuously cut the magnetic flux lines, generate induced current and electromagnetic torque, and keep the motor running.
Characteristics and advantages of induction motors
(I) Simple structure and reliable operation
Induction motors do not have complex commutators and brushes and other components, especially squirrel cage induction motors, whose rotor structure is strong and not easy to damage. This makes induction motors have the advantages of simple structure, convenient manufacturing, reliable operation, and low maintenance cost, and are widely used in industrial production and daily life.
(II) Easy to achieve speed regulation and forward and reverse rotation
The speed of the induction motor can be easily adjusted by changing the frequency and voltage of the power supply or by inserting a resistor in series in the winding rotor circuit. At the same time, changing the phase sequence of the three-phase current can easily achieve the forward and reverse rotation of the motor to meet the needs of different working conditions.
(III) High efficiency
Under reasonable design and operating conditions, induction motors can convert most electrical energy into mechanical energy, have high energy conversion efficiency, and effectively reduce energy consumption.
With its ingenious electromagnetic principle and unique structural design,induction motors inject a steady stream of power into our lives and production. From the electromagnetic induction phenomenon to the generation of a rotating magnetic field, and then to the rotation of the rotor, every link embodies human wisdom and creativity. With the continuous development of science and technology, induction motors are also continuously innovating and optimizing, and will play an important role in more fields in the future. I hope that through this article, you can have a deeper understanding of the working principle of induction motors and feel the magical charm of the electromagnetic world.