What are the classifications of AC motors?

Types of AC Motors

AC motors (AC Motors) are a widely used class of motors that can be classified based on different working principles, structures, and applications. Below are the main categories of AC motors and their characteristics:

1. Induction Motors

1.1 Squirrel Cage Induction Motor

Structure: The rotor is made of cast aluminum or copper bars, shaped like a squirrel cage, hence the name.

Characteristics:

Simple structure, low cost, and easy maintenance.

High starting current but moderate starting torque.

High efficiency during operation, widely used in various industrial and household applications.

Applications: Fans, pumps, compressors, conveyors, etc.

1.2 Wound Rotor Induction Motor

Structure: The rotor consists of three-phase windings and can be connected to external resistors.

Characteristics:

High starting torque, and starting current and torque can be adjusted using external resistors.

Good speed regulation, suitable for applications requiring speed control.

Complex structure, higher cost.

Applications: Cranes, large machinery, metallurgical equipment, etc.

2. Synchronous Motors

2.1 Non-Excited Synchronous Motor

Structure: The rotor does not have a separate excitation winding and relies on the induction from the stator field to produce the rotor field.

Characteristics:

Simple structure, low cost.

Operates in synchronism with the stator field, high power factor.

Difficult to start, usually requires auxiliary starting devices.

Applications: Precision instruments, constant-speed drives, etc.

2.2 Excited Synchronous Motor

Structure: The rotor has a separate excitation winding, typically powered by a DC source.

Characteristics:

High power factor and efficiency during operation.

Power factor and torque can be adjusted by regulating the excitation current.

Complex structure, higher cost.

Applications: Large generators, large motors, power system peak shaving, etc.

3. Permanent Magnet Synchronous Motors (PMSM)

Structure: The rotor uses permanent magnets, and the stator uses three-phase windings.

Characteristics:

High efficiency and power density.

High control accuracy, suitable for high-precision applications.

High starting torque, fast dynamic response.

Higher cost but superior performance.

Applications: Servo systems, robots, electric vehicles, precision equipment, etc.

4. Brushless DC Motors (BLDC)

Structure: The rotor uses permanent magnets, and the stator uses an electronic commutator.

Characteristics:

Brushless design, long life, and minimal maintenance.

Flexible control, wide speed range.

High efficiency, fast dynamic response.

Higher cost but superior performance.

Applications: Computer fans, drones, home appliances, industrial automation, etc.

5. Single-Phase AC Motors

Structure: Powered by a single-phase AC supply, the rotor is typically a squirrel cage rotor.

Characteristics:

Simple structure, low cost.

Low starting torque, lower efficiency during operation.

Suitable for low-power applications.

Applications: Household appliances (e.g., refrigerators, washing machines, air conditioners), small machinery, etc.

6. AC Servo Motors

Structure: Usually a permanent magnet synchronous motor or a brushless DC motor equipped with an encoder or other position feedback device.

Characteristics:

High-precision positioning, fast dynamic response.

Flexible control, wide speed range.

Higher cost but superior performance.

Applications: CNC machines, robots, automated production lines, etc.

Summary

AC motors can be classified into various types based on their working principles, structures, and application characteristics. Selecting the appropriate type of AC motor requires considering specific application requirements, such as power, torque, speed, speed regulation range, cost, and maintenance.