What is the principle of AC motor drive

Alternating current. Principles of Motivation Drive:

The AC motor consists of a stator and a rotor.

AC motors are divided into two types: synchronous AC motors and induction motors. Both motors are stator side windings that are fed with alternating current to generate a rotating magnetic field, but the rotor windings of synchronous AC motors usually require direct current (excitation current) to be supplied to the exciterIn the case of induction motors, no current is required to be applied to the rotor windings.

1. Induction motor.

The structure of the synchronous motor is roughly the same as that of the alternator, and the difference between it and the base wood of the induction motor is that its rotor is a convex pole wound around a coil, and the direct current is supplied by another exciter.

Synchronous motors are AC motors, and the stator windings are the same as asynchronous motors. Its rotor rotation speed is the same as the speed of the rotating magnetic field generated by the stator windings, so it is called a synchronous motor. Because of this, the current of the synchronous motor is ahead of the voltage in phase, i.e. the synchronous motor is a capacitive load.

For this reason, synchronous motors are often used to improve the power factor of the power supply system.

Target. 2. Synchronous motor.

Induction motor is also known as "asynchronous motor", that is, the rotor is placed in a rotating magnetic field, and under the action of the rotating magnetic field, a rotating torque is obtained, so the rotor rotates. The appearance and internal structure of the induction motor rotor is a rotating conductor, usually in the shape of a squirrel cage. The stator is the non-rotating part of the electric motor whose main task is to generate a rotating magnetic field.

A rotating magnetic field is not achieved mechanically. Instead, it is passed through several pairs of electromagnets with alternating current.

, so that the polarity properties of the pole change cyclically, so it is equivalent to a rotating magnetic field.

This kind of motor is not like a DC motor.

There are brushes or collector rings, depending on the type of alternating current used, there are single-phase motors and three-phase motors, single-phase motors are used in washing machines, electric fans.

etc.;Three-phase electric motors are used as the plant's power equipment.

The relative motion of the rotating magnetic field generated by the stator (the rotational speed of which is synchronous speed n1) and the rotor windings.

The rotor windings cut the magnetic inductance lines to generate an induced electromotive force.

This results in an induced current in the rotor windings. The induced current in the rotor windings acts with the magnetic field to generate electromagnetic torque, which causes the rotor to rotate. Because when the rotor speed is gradually close to the synchronous speed, the induced current gradually decreases, and the generated electromagnetic torque also decreases accordingly, when the asynchronous motor works in the motor state, the rotor speed is less than the synchronous speed.

To describe the difference between the rotor speed n and the synchronous speed n1, the slip rate is introduced.

The principle of AC motor drive is mainly to use the magnetic field generated by AC power supply to act on the coil in the motor to make the motor rotate.

It is to use the principle of electromagnetic induction to generate an alternating magnetic field through the changing direction and magnitude of the current to drive the motor to rotate. The AC motor is mainly composed of two parts: a stator and a rotor.

The stator is made up of several coils in which an alternating current is passed to produce a rotating magnetic field.

The rotor is composed of several conductors, and there is also an electric current in the conductor to generate an induced electromotive force, so that the rotor is subjected to magnetic force and rotates.

In addition, the AC motor is driven by sending a three-phase alternating current to a fixed stator winding, which generates a rotating magnetic field to induce the closed rotor winding to generate an electric current, and the rotor rotates in the direction of rotation of the rotating magnetic field under the action of electromagnetic force.

In addition, the heat of the AC motor is mainly generated in the stator coil of the motor housing, which is convenient for cooling and heat dissipation.

Therefore, AC motors require fewer components than DC motors, and there are no wearing parts that need to be replaced regularly, making them more efficient, more durable, and more durable.

27.Single-phase AC motor principle and its connection. Middle.

Model 3 Motor Controller, Drive Circuit Schematic Explanation!

Liang Bo principle: The AC motor is based on the characteristics of alternating current, in the slag of the fixed slag in the winding to generate a rotating magnetic field, and then make the rotor coil do the movement of cutting the magneto's induction line, so that the rotor coil produces induced current, and the induced magnetic field generated by the induced current is opposite to the direction of the magnetic field of the stator, so that the rotor has a rotating torque, that is, the coil can continue to rotate.

An alternating current motor is a machine that converts the electrical energy of alternating current into mechanical energy. An AC motor is mainly composed of an electromagnet winding or distributed stator winding to generate a magnetic field and a rotating armature or rotor. The electric motor is made by using the phenomenon of energized coils rotating under force in a magnetic field.

The AC motor is composed of a stator and a rotor, and the stator and the rotor use the same power supply, so the direction change of the current in the stator and rotor is always synchronized, that is, the direction of the current in the coil changes, and the direction of the current in the electromagnet also changes, according to the left-hand rule, the direction of the magnetic force on the coil remains unchanged, and the coil can continue to rotate.

The principle of rotation of a single-phase AC motor.

Single-phase AC motors have only one winding, and the rotor is squirrel cage type. Single-phase electricity cannot produce a rotating magnetic field. To make the single-phase motor can rotate automatically, we can add a starting winding in the stator, the starting winding and the main winding are 90 degrees apart in space, and the starting winding should be connected in series with a suitable capacitor, so that the current with the main winding is approximately 90 degrees different in phase, that is, the so-called phase splitting principle.

In this way, two currents that differ by 90 degrees in time flow into two windings that differ by 90 degrees in space, and a rotating magnetic field (two-phase) is generated in space, under the action of which the rotor can start automatically.

The rotation principle of a three-phase asynchronous motor.

The prerequisite for a three-phase asynchronous motor to rotate is to have a rotating magnetic field, and the stator winding of the three-phase asynchronous motor is used to generate a rotating magnetic field. We know that the voltage between the phases of the three-phase power supply is 120 degrees different in phase, and the three windings in the stator of the three-phase asynchronous motor are also 120 degrees different from each other in the spatial orientation, so that when the three-phase power supply is passed into the stator winding, the stator winding will produce a rotating magnetic field, after the stator winding produces a rotating magnetic field, the rotor conductor (squirrel cage bar) will cut the magnetic field lines of the rotating magnetic field and produce an induced current, and the current in the rotor guide bar interacts with the rotating magnetic field to produce electromagnetic force, The electromagnetic torque generated by the electromagnetic force drives the rotor to rotate in the direction of the rotating magnetic field. In general, the actual speed of the motor is lower than the speed of the rotating magnetic field.

For this reason, we call the three-phase motor an asynchronous motor.

Typically, the circuits used to drive motors are divided into two categories: DC circuits and AC circuits. Below I will introduce you to some commonly used circuits.

1.DC motor direct drive circuit.

The DC motor direct drive circuit refers to the DC power supply directly connected to the DC motor, and the control switch is used to control the speed of the motor. This circuit is simple and easy to understand, but it does not have a speed adjustment function.

2.DC motor intermittent drive circuit.

The DC motor intermittent drive circuit refers to the control of the DC power supply, so that the speed of the DC motor is adjustable. Such circuits are usually implemented using ordinary thyristors.

3.DC motor speed regulation circuit.

The DC motor speed regulation circuit refers to the use of a frequency converter or governor to adjust the speed of the DC motor. This circuit can realize the precise control of the motor speed, and is suitable for applications that require high-precision adjustment.

4.AC motor drive circuit.

The AC motor drive circuit refers to connecting the AC power supply to the AC motor and using the control switch to control the speed of the motor. This circuit is simple and easy to understand, but there is no speed adjustment function.

5.AC motor speed regulation circuit.

AC motor speed regulation circuit refers to the use of a governor or frequency converter to adjust the speed of AC motor. This circuit can realize precise and accurate control of the motor speed, which is suitable for occasions that require high-precision adjustment.

1. The principle of power generation The basic principle of alternating current generated by alternator is the principle of electromagnetic induction. When the rotor winding of the generator is connected to direct current, a magnetic field is generated, the rotor rotates under the drive of the engine, and the stator winding cuts the rotor magnetic field to induce a three-phase AC electromotive force. Second, the principle of rectification, the rectifier circuit converts the three-phase electromotive force into DC pulsating voltage; Since the battery has the function of a capacitor, the output DC voltage waveform is relatively flat.

When the generator is running at no load, ignoring the resistance voltage drop of the three-phase winding and rectifier, the DC electromotive force is about: U = is the phase electromotive force). 3. Excitation method: The rotor windings of the generator generate a magnetic field, which is called excitation.

There are two ways of generator excitation: separate excitation and self-excitation. (1) When the speed of the generator is low (the engine does not reach idle speed), it cannot generate electricity by itself, and the battery needs to provide current to the excitation winding of the generator, so that the excitation winding can generate a magnetic field to generate electricity.

This method of generating electricity by supplying excitation current from the battery is called other excitation power generation. (2) With the increase of the speed, the electromotive force of the stator winding of the generator gradually increases, and the rectifier diode can be turned on. When the output voltage of the generator is greater than the battery voltage, the generator can supply power to the outside world, and at this time, it can supply its own electricity to the excitation winding, which is called self-excited electricity.