I. Classification of AC Motors
An "AC motor" is a machine used to convert mechanical energy into alternating current (AC) electrical energy. Due to the rapid development of AC power systems, AC motors have become the most commonly used type of motor. Compared to DC motors, AC motors lack a commutator (see commutation in DC motors), resulting in a simpler structure, easier manufacturing, greater robustness, and ease of production into high-speed, high-voltage, high-current, and high-capacity motors. The power range of AC motors is vast, from a few watts to hundreds of thousands or even millions of kilowatts. In the early 1980s, the largest steam turbine generators reached 1.5 million kilowatts.
AC motors can be classified into several types according to different classification standards. The following are some common classification methods:
1. Classification according to electromagnetic excitation method: DC motor, asynchronous motor, synchronous motor, stepper motor, etc.
2. Classification by rotor structure: External rotor motors and internal rotor motors.
3. Classification according to load characteristics: Inductive load motors, capacitive load motors, and resistive load motors.
4. Classification by mechanical structure: Asynchronous motors (squirrel-cage type) and asynchronous motors (wound-rotor type)
5. Classified by power: micro motors, low-power motors, medium-power motors, high-power motors, etc.
An AC motor is a device that converts mechanical energy into alternating current (AC) electrical energy. It can be classified into the following categories:
1. According to their function, they are divided into two main categories: AC generators and AC motors. AC motors are devices that convert AC electrical energy into mechanical energy.
2. Based on their different operating principles, AC motors can be divided into two main categories: synchronous motors and asynchronous motors. The rotational speed of a synchronous motor has a strict correspondence with the frequency of AC, and its speed remains strictly constant during operation. The speed of an asynchronous motor changes slightly with the load.
3. Based on the required number of AC power phases, AC motors can be divided into two main categories: single-phase and three-phase. Currently, the most widely used is the three-phase asynchronous motor, due to its advantages such as simple structure, low price, robustness, durability, and ease of use and maintenance. Single-phase asynchronous motors are widely used in situations where three-phase power is unavailable and for some smaller power applications.
4. Three-phase asynchronous motors can be divided into two main categories based on their rotor structure: squirrel-cage type and wound-rotor type, with the squirrel-cage type being the most widely used.
II. Application Principles of AC Motors
Through the above introduction, you should now have a basic understanding of AC motors. In this section, we will mainly discuss the application principles of AC motors.
The principle of an AC motor refers to the use of the magnetic field generated by an alternating current (AC) power supply to act on the coils in the motor, thereby causing the motor to rotate. Simply put, it utilizes the principle of electromagnetic induction. By using a constantly changing current with varying direction and magnitude, an alternating magnetic field is generated, which drives the motor to rotate. An AC motor mainly consists of two parts: a stator and a rotor. The stator is composed of several coils, through which an alternating current flows, generating a rotating magnetic field. The rotor is composed of several conductors, through which current also flows, generating an induced electromotive force, causing the rotor to rotate under the influence of a magnetic force.
The speed of an AC motor can be adjusted by changing the power supply frequency; AC motors can be divided into two types: asynchronous motors and synchronous motors, with different applications; AC motors can also be used to manufacture various mechanical equipment such as fans, water pumps, and compressors. In short, the principle of AC motors is an important foundational knowledge in motor learning. Mastering the working principle of AC motors can help us better understand the characteristics and applications of motors, thus enabling us to better apply them in actual production.
When an AC power source is connected to the motor, the coils in the stator are energized, generating a rotating magnetic field. Since the conductors in the rotor also carry current, an induced electromotive force is generated under the influence of the rotating magnetic field, causing the rotor to rotate due to the magnetic force. At the same time as the rotor is subjected to the magnetic force, it also generates a reverse magnetic field, which interacts with the rotating magnetic field, causing the rotor to continue rotating.
