Types Of Electric Motors

What is the working principle of the motor? The motor is a device that converts electrical energy into mechanical energy. It uses an energized coil, that is, a stator winding, to generate a rotating magnetic field and act on the rotor to form a magnetic-electromotive force rotation torque. The motor is a rotating machine that converts electrical energy into mechanical energy. It mainly includes an electromagnet winding or a distributed stator winding for generating a magnetic field and a rotating armature or rotor. The current passes through the wire and is rotated by the magnetic field. Some types of these machines can be used as motors or generators.

The motor is a device that converts electrical energy into mechanical energy. It is made by using the phenomenon that the energized coil rotates under force in the magnetic field. It is distributed at various users. The motor is divided into DC motors and AC motors according to the power supply used. Most of the motors in the power system are AC motors, which can be synchronous motors or asynchronous motors (the speed of the motor stator magnetic field does not keep the same speed as the rotor rotation speed). The motor is mainly composed of a stator and a rotor. The direction of the force movement of the energized wire in the magnetic field is related to the direction of the current and the direction of the magnetic flux lines (magnetic field direction). The working principle of the motor is that the magnetic field acts on the force of the current to make the motor rotate.

Types of motors

1. Classification by working power supply: According to the different working power supplies of motors, they can be divided into DC motors and AC motors. Among them, AC motors are also divided into single-phase motors and three-phase motors.

2. Classification by structure and working principle: Motors can be divided into DC motors, asynchronous motors and synchronous motors according to their structure and working principle.

Synchronous motors can also be divided into permanent magnet synchronous motors, reluctance synchronous motors and hysteresis synchronous motors.

Asynchronous motors can be divided into induction motors and AC commutator motors. Induction motors are further divided into three-phase asynchronous motors, single-phase asynchronous motors and shaded pole asynchronous motors. AC commutator motors are further divided into single-phase series motors, AC/DC dual-purpose motors and repulsion motors.

DC motors can be divided into brushless DC motors and brushed DC motors according to their structure and working principle. Brushed DC motors can be divided into permanent magnet DC motors and electromagnetic DC motors. Electromagnetic DC motors are further divided into series-excited DC motors, shunt-excited DC motors, separately-excited DC motors and compound-excited DC motors. Permanent magnet DC motors are further divided into rare earth permanent magnet DC motors, ferrite permanent magnet DC motors and aluminum nickel cobalt permanent magnet DC motors.

3. Classification by starting and running mode: Motors can be divided into capacitor-start single-phase asynchronous motors, capacitor-run single-phase asynchronous motors, capacitor-start-run single-phase asynchronous motors and split-phase single-phase asynchronous motors according to their starting and running modes.

4. Classification by purpose: Motors can be divided into drive motors and control motors according to their purpose.

Drive motors are further divided into motors for power tools (including drilling, polishing, grinding, grooving, cutting, reaming and other tools), motors for household appliances (including washing machines, electric fans, refrigerators, air conditioners, recorders, video recorders, DVD players, vacuum cleaners, cameras, hair dryers, electric shavers, etc.) and motors for other general small mechanical equipment (including various small machine tools, small machinery, medical equipment, electronic instruments, etc.). Control motors are further divided into stepper motors and servo motors, etc.

5. Classification by rotor structure: Motors can be divided into cage induction motors (called squirrel cage asynchronous motors in the old standard) and wound rotor induction motors (called wound asynchronous motors in the old standard) according to the structure of the rotor.

6. Classification by operating speed: Electric motors can be divided into high-speed motors, low-speed motors, constant-speed motors, and speed-regulating motors according to their operating speed.

a. Low-speed motors can be divided into gear reduction motors, electromagnetic reduction motors, torque motors, and claw-pole synchronous motors.

b. In addition to being divided into step-by-step constant-speed motors, stepless constant-speed motors, step-by-step variable-speed motors, and stepless variable-speed motors, speed-regulating motors can also be divided into electromagnetic speed-regulating motors, DC speed-regulating motors, PWM variable-frequency speed-regulating motors, and switched reluctance speed-regulating motors.

Servo motors

A micro motor used as an actuator in an automatic control device. Also known as an executive motor. Its function is to convert electrical signals into angular displacement or angular velocity of the rotating shaft.

Servo motors are divided into two categories: AC and DC. The working principle of an AC servo motor is the same as that of an AC induction motor. On the stator, there are two excitation windings Wf and control windings WcoWf with a phase space displacement of 90° electrical angle connected to a constant AC voltage. The purpose of controlling the operation of the motor is achieved by using the AC voltage or phase change applied to Wc. AC servo motors have the characteristics of stable operation, good controllability, fast response, high sensitivity, and strict nonlinearity indicators of mechanical characteristics and adjustment characteristics (required to be less than 10% to 15% and less than 15% to 25% respectively). The working principle of DC servo motors is the same as that of general DC motors.

The motor speed n is n = E / K1j = (Ua-IaRa) / K1j, where E is the armature back electromotive force; K is a constant; j is the flux per pole; Ua, Ia are the armature voltage and armature current; Ra is the armature resistance. Changing Ua or changing φ can control the speed of the DC servo motor, but the method of controlling the armature voltage is generally used. In permanent magnet DC servo motors, the excitation winding is replaced by permanent magnets, and the flux φ is constant.

DC servo motors have good linear adjustment characteristics and fast time response.

Servo motors are generally divided into DC servo and AC servo. The advantages of DC servo motors are:

Advantages: precise speed control, very hard torque-speed characteristics, simple principle, easy to use, price advantage;

Disadvantages: brush commutation, speed limit, additional resistance, wear particles (for clean rooms).

For AC servo motors

Advantages: good speed control characteristics, smooth control can be achieved in the entire speed range, almost no oscillation; high efficiency, more than 90%, no heat; high-speed control; high-precision position control (depending on the type of encoder); constant torque in the rated operating area; low noise; no brush wear, maintenance-free; no wear particles, no sparks, suitable for clean rooms, low inertia in explosive environments;

Disadvantages: more complex control, drive parameters need to be adjusted on-site PID parameter setting, more wiring required

Application of DC servo motors

The characteristics of DC servo motors are harder than those of AC servo motors. Usually used in systems with slightly higher power, such as position control in follow-up systems.

Application of AC servo motors

The output power of AC servo motors is generally 0.1-100W, and the power supply frequency is divided into 50Hz, 400Hz, etc. It is widely used, such as in various automatic control, automatic recording and other systems.