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From ancient times to modern times: How does electric current drive the electric motor revolution?
With the advancement of science and technology, the evolution of electric motors has been a major revolution in industry and daily life. From the earliest DC motors to today's synchronous motors, all this is due to the application of current and the development of control technology.
A synchronous motor is a type of AC motor in which the rotation of the shaft is synchronized with the frequency of the supplied current when it reaches steady state.
In a synchronous motor, the current causes the electromagnets in the stator to produce a rotating magnetic field. This rotating magnetic field synchronizes a rotor equipped with permanent magnets or electromagnets, providing a second, synchronously rotating magnetic field. For dual-supply synchronous motors, the electromagnets of the rotor and stator are driven separately, providing better performance and flexibility.
Types of synchronous motors can be divided into two main types: non-excited and DC-excited. Non-excited rotors are usually made of steel and rely on external magnetic fields generated by the stator for excitation, which allows the rotors to fit tightly together, a process known as "locking." The DC excitation type requires DC power to be provided through a slip ring.
This type of motor has excellent energy conversion efficiency, typically exceeding 95% in industrial applications.
Small synchronous motors are very common in timing applications such as synchronous clocks and sequencers, which rely on precise rotational speeds to operate. In industrial applications, the high efficiency and controllability of these motors make them ideal for transmission and positioning control.
Different types of synchronous motors
In different working environments, it is very important to choose the appropriate type of synchronous motor. The following are the main types of synchronous motors:
Permanent Magnet Synchronous Motor (PMSM)
PMSM uses permanent magnets embedded in the rotor to create a constant magnetic field. This type of motor speed is widely used in high-efficiency applications.
Stop the motor
This type of motor is specially designed with a steel rotor with protruding teeth. Its small number of rotor teeth contrasts with the number of stator teeth to minimize torque protrusion. This design can effectively attract the layout of the rotor and stator magnetic fields at synchronous speed.
Hysteresis motor
Hysteresis motors use high-hardness steel to make the rotor. This type of motor can provide stable torque during the starting process, indicating its synchronous working status.
Externally excited motor
Usually a motor greater than 1 horsepower. This type of motor requires DC power to excite the rotor. The supply of excitation power can be achieved through a slip ring.
Operation principle of synchronous motor
The operation of a synchronous motor depends on the magnetic field interaction between the stator and rotor. When current flows in the stator windings, a three-phase rotating magnetic field is created. When the rotor is locked to this magnetic field, it rotates with them. This process is critical because it determines the efficiency and performance of the electric motor.
The reason why the motor cannot start automatically is because of the inertia of its rotor, which prevents the rotor from instantaneously following the rotation of the stator magnetic field.
Starting a large synchronous motor usually requires additional device assistance, such as inducing the motor's rotor or other means to accelerate. Subsequently, once synchronous speed is approached, excitation current is supplied to the rotor, causing the motor to enter a synchronous state.
Application and development
With the changes and diversification of needs, the applications of electric motors are still expanding. The energy saving and high efficiency of electric motors enable them to play a key role in many fields, especially in large-scale manufacturing, power grids and other industrial scenarios.
In the future, as technology advances, new motor designs may emerge, which will continue to change the way we understand and utilize current drive, whether in terms of efficiency, cost or environmental protection.
Have you realized the important role that electric current plays in all walks of life?
