An electric motor (English: Electric machinery, commonly known as a "motor") is an electromagnetic device that converts or transmits electrical energy based on the law of electromagnetic induction. It is divided into electric motors (symbol M) and generators (symbol G).
Electric motors are products manufactured based on electromagnetic effects, equivalent to the "internal combustion engine" in a gasoline-powered car. They convert electrical energy into mechanical energy, with an energy conversion efficiency typically exceeding 85%. Their efficiency is directly proportional to power; the higher the power, the higher the conversion rate. Their development can be broadly summarized into four stages: supercharged motor stage → alternating current motor stage → control motor stage → special-purpose motor stage.
Over the years, through different stages of development, motors can be classified into different types according to their dimensions. According to their power supply, they can be divided into DC motors and AC motors, which can be further subdivided, as we will discuss below. According to their structure and working principle, they can be divided into DC motors, asynchronous motors, and synchronous motors.
The most common types of motors today are DC motors, asynchronous motors, permanent magnet synchronous motors, and switched reluctance motors. Today, we'll start by talking about DC motors and asynchronous motors.
Motors are mainly classified into three categories: control motors, power motors, and signal motors.
Control motor
The types of motors that can be controlled include: brushless DC motors, stepper motors, servo motors, torque motors, and switched reluctance motors.
For example, servo motors are widely used in various control systems. They can convert input voltage signals into mechanical output on the motor shaft, driving the controlled components to achieve the control objective.
Power motor
Power motors include: DC motors, asynchronous motors, and synchronous motors.
For example, a DC motor, when it operates as a motor, converts electrical energy into mechanical energy; when it operates as a generator, it converts mechanical energy into electrical energy.
Signal motor
Signal motors include: position signal motors and speed signal motors.
For example, rotary transformers, inductive synchros, and synchros are all types of position signal motors.
Motor Introduction
An electric motor is an electromagnetic device that converts or transmits electrical energy based on the law of electromagnetic induction. The main function of an electric motor is to generate driving torque, serving as a power source for electrical appliances or various machines. A generator, represented by the letter G in a circuit, primarily converts electrical energy into mechanical energy.
Basic working principle of electric motor
1. Classified by working power supply
Based on the different power sources used to operate the motor, motors can be divided into DC motors and AC motors. AC motors are further divided into single-phase motors and three-phase motors.
2. Classification by structure and working principle
Electric motors can be classified into synchronous motors and asynchronous motors according to their structure and working principle.
Synchronous motors can be classified into water-magnetic synchronous motors, reluctance synchronous motors, and hysteresis synchronous motors.
Asynchronous motors can be divided into induction motors and AC commutating motors. Induction motors are further divided into three-phase asynchronous motors, single-phase asynchronous motors, and shaded-pole asynchronous motors. AC commutating motors are further divided into single-phase series motors and AC/DC universal motors.
The basic working principle of an electric motor is that a magnetic field exerts a force on an electric current, causing the motor to rotate. A current-carrying conductor in a magnetic field will experience a force, which manifests macroscopically as the Ampere force and microscopically as the Lorentz force on a moving charge.
Electric motors can be classified into synchronous motors and asynchronous motors according to their structure and working principle.
Synchronous motors can be classified into water-magnetic synchronous motors, reluctance synchronous motors, and hysteresis synchronous motors.
Asynchronous motors can be divided into induction motors and AC commutating motors. Induction motors are further divided into three-phase asynchronous motors, single-phase asynchronous motors, and shaded-pole asynchronous motors. AC commutating motors are further divided into single-phase series motors and AC/DC universal motors.
Key point: When a conductor is closed into a circuit and placed near a coil carrying alternating current, an induced current will be generated in the conductor due to electromagnetic induction. An electric motor that operates based on the interaction between the magnetic field of the induced current and the magnetic field of the current-carrying coil is called an induction motor. A motor powered by a single-phase power supply is called a single-phase induction motor, and one powered by a three-phase power supply is called a three-phase induction motor.
A commutator motor is a type of electric motor that connects a conductor to a battery or other power source to form a circuit, allowing the power source to directly supply current to the conductor in the magnetic field. The rotor coil of the motor is directly powered by the power source, and the current is guided into the rotating rotor coil through brushes and a commutator.
DC motors can be classified into brushed DC motors and brushed DC motors according to their structure and working principle. Brushed DC motors can be further divided into electromagnetic DC motors and permanent magnet DC motors. Electromagnetic DC motors are further divided into series-wound DC motors, shunt-wound DC motors, separately excited DC motors, and compound-wound DC motors. Permanent magnet DC motors are further divided into rare-earth permanent magnet DC motors, ferrite hydromagnetic DC motors, and AlNiCo permanent magnet DC motors.
3. Classified by startup and operation mode
Electric motors can be classified according to their starting and running methods into capacitor-start motors, capacitor-run motors, capacitor-start-run motors, and split-phase motors.
4. Classified by purpose
Electric motors can be classified into drive motors and control motors according to their uses.
Electric motors for driving are further divided into electric motors for power tools (including drilling, polishing, grinding, grooving, cutting, reaming, etc.), electric motors for household appliances (including washing machines, electric fans, refrigerators, air conditioners, tape recorders, video recorders, DVD players, vacuum cleaners, cameras, hair dryers, electric shavers, etc.), and electric motors for other general-purpose small mechanical equipment (including various small machine tools, small mechanical medical devices, electronic instruments, etc.).
Control motors are further divided into stepper motors and servo motors, etc.
5. Classification by rotor structure
Electric motors can be classified into squirrel-cage induction motors and wound-rotor induction motors according to the structure of their rotors.
6. Classified by operating speed
Electric motors can be classified according to their operating speed into high-speed motors, low-speed motors, constant-speed motors, and variable-speed motors.
Low-speed electric motors are further classified into geared motors, electromagnetic geared motors, torque motors, and claw-pole synchronous motors, etc.
In addition to being classified into stepped constant speed motors, stepless constant speed motors, stepped variable speed motors, and stepless variable speed motors, speed-regulating motors can also be classified into electromagnetic speed-regulating motors, DC speed-regulating motors, PWM frequency conversion speed-regulating motors, and switched reluctance speed-regulating motors.
