2023

What is the principle of an electric motor?

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A machine that converts electrical energy into mechanical energy. 1) DC motor - A motor that uses DC current to rotate is called a DC motor. Due to the different ways in which the magnetic field circuit is connected to the armature circuit, it can also be divided into series excited motors, split excited motors, and compound excited motors; (2) AC motor - An electric motor that uses AC current to rotate is called an AC motor. There are many types, mainly including: ① Rectifier motors - series excited DC generators used as AC motors, which are called this type of motor. Due to the simultaneous rotation of AC current in the magnetic field and armature circuit, the direction of the couple moment remains constant, and the machine does not stop rotating. This type of motor is also known as a "universal motor" because it can use both AC and DC. This type of motor is commonly used in vacuum cleaners, sewing machines, and other household appliances Synchronous motor - a motor whose armature rotates from one pole to the next, exactly in the same cycle as the rotation of the incoming current. This type of motor cannot be started on its own and must be wound with another motor or special auxiliary wire to reach the appropriate frequency before AC power can be connected. If the load changes and the speed changes, the speed will not match the AC frequency, which is enough to cause disorder in its pace, tend to stop or cause damage. Due to many limitations, it is not widely used Induction motor - a device that places the rotor in the rotating magnetic field and makes the rotor rotate due to the effect of Eddy current. The rotating magnetic field is not caused by mechanical methods, but rather by alternating current flowing through several pairs of electromagnets, causing cyclic changes in their magnetic polarity, which can be regarded as a rotating magnetic field. Usually, three-phase induction motors (with three pairs of magnetic poles) are used. The motion of a DC motor is exactly opposite to that of a DC generator, where the induced current is formed by the induced electromotive force, so they are in the same direction. In an electric motor, the direction of the induced electromotive force supplied by an external power source is opposite to the direction of the armature current I. For induction motors in AC motors, the strong induced current (eddy current) is generated in the rotating magnetic field. The copper bar on the rotor continuously cuts the magnetic line of force. According to Lenz's law, this induced current has the effect of resisting the relative movement between the magnetic field and the rotor, so the rotor rotates with the magnetic field. However, the rotational speed of this rotor is not as high as the speed of magnetic field transformation, otherwise the magnetic field lines will not be cut by the copper rod.

Jul 25,2023