How does an AC motor work? How does an alternator work?

It's like why people sleep, and it's really bad. The motor is not explained by the principle of same-sex repulsion and opposite-sex attraction, the motor due to the phase relationship of the power supply, the generation is a rotating magnetic field, when the stator is connected to the power supply, you put an iron ball in the stator, you will find that the iron ball is running with the rotating magnetic field, the motor wiring is to produce the number of pole pairs of the motor, no matter how many pairs of magnetic poles, in the stator each next to each single pole must be one reverse and one positive, the wiring is correct, the principle is to adapt to the frequency of alternating current, produce a smooth rotating magnetic field. The principle of rotation of various AC motors.

At present, there are two kinds of AC motors that are commonly used: 1. Three-phase asynchronous motors. 2. Single-phase AC motor. The first is mostly used in industry, while the second is mostly used in civil appliances.

1. The rotation principle of 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 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 introduced in the stator winding, the stator winding will produce a rotating magnetic field, and the process of its generation is shown in Figure 1. The diagram depicts the generation of a rotating magnetic field in four moments.

For each period of the current change, the rotating magnetic field rotates once in space, i.e., the rotational speed of the rotating magnetic field is synchronized with the change of the current. The rotational speed of the rotating magnetic field is: n=60f where f is the frequency of the power supply, p is the number of pole pairs of the magnetic field, and the unit of n is:

Revolutions per minute. According to this formula, we know that the speed of the motor is related to the number of poles and the frequency of the power supply, for this reason, there are two ways to control the speed of the AC motor: 1. Change the magnetic pole method; 2. Frequency conversion method.

In the past, the first method was often used, but now the frequency conversion technology is used to realize the stepless variable speed control of the AC motor.

Looking at Figure 1, it can also be seen that the direction of rotation of the rotating magnetic field is related to the phase sequence of the current in the winding. If any two of the three power lines are reversed, for example, phase B current is passed into phase C winding, and phase C current is charged into phase B winding, then the phase sequence becomes: C, B, A, then the magnetic field must rotate counterclockwise.

This feature allows us to easily change the direction of rotation of a three-phase motor. After the stator winding generates a rotating magnetic field, the rotor guide strip (squirrel cage bar) will cut the magnetic field lines of the rotating magnetic field and generate an induced current, and the current in the rotor guide strip interacts with the rotating magnetic field to produce electromagnetic force, and the electromagnetic torque generated by the electromagnetic force drives the rotor to rotate at a speed of n1 along the direction of the rotating magnetic field. In general, the actual speed n1 of the motor is lower than the speed n of the rotating magnetic field.

Because assuming n=n1, then there is no relative motion between the rotor guide bar and the rotating magnetic field, the magnetic field lines will not be cut, and the electromagnetic torque will not be generated, so the rotational speed n1 of the rotor must be less than n. For this reason, we call the three-phase motor an asynchronous motor.

The stator of the motor has coil windings that generate a rotating magnetic field when an alternating current is applied. The motor rotor is manufactured with a squirrel cage-like conductor embedded. This conductor is induced by a rotating magnetic field to produce an electric current which also produces a magnetic field.

This magnetic field is attracted by the rotating magnetic field of the stator, which drives the rotor to rotate. This is the basic principle of AC motors. From those who love to ask knowledge.

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

How the integral alternator works.

When the external circuit energizes the excitation winding through the brush, a magnetic field is generated, which magnetizes the claw pole into the n pole and the S pole. When the rotor rotates, the magnetic flux changes alternately in the stator winding, and according to the principle of electromagnetic induction, an alternating induced electromotive force is generated in the three-phase winding of the stator. This is how the alternator generates electricity.

The synchronous generator rotor of the DC excitation is dragged by the prime mover (i.e., the engine) and rotates at a speed n (rpm), and the three-phase stator induces the alternating current potential around the resistance. If the stator winding is connected to the electrical load, the motor has an alternating current output, and the alternating current is converted into direct current through the rectifier bridge inside the generator and output from the output terminal.

The alternator is divided into two parts: stator winding and rotor winding, the three-phase stator winding is distributed on the shell according to the electric angle of 120 degrees different from each other, and the rotor winding is composed of two pole claws. When the rotor windings are connected to the direct current, they are excited, and the two pole claws form the n pole and the s pole. The magnetic field lines start from the n-pole, enter the stator core through the air gap, and return to the adjacent s-pole.

Once the rotor rotates, the rotor winding will cut the magnetic field lines, and a sinusoidal electromotive force with an electrical angle of 120 degrees in the stator winding will be generated, that is, three-phase alternating current, which will be changed to direct current output through the rectifier element composed of diodes.

When the switch is closed, the battery first supplies the current. The circuit is:

The positive electrode of the battery, the charging indicator, the regulator contact, the excitation winding resistance, and the negative electrode of the iron battery. At this time, the charging indicator light will be on due to the current passing through it.

However, after the engine starts, as the speed of the generator increases, the terminal voltage of the generator also increases. When the output voltage of the generator is equal to the battery voltage, the potential of the "B" and "D" ends of the generator is equal, and at this time, the charging indicator is extinguished due to the zero potential difference between the two ends. Indicates that the generator is working normally, and the excitation current is supplied by the generator from the trouser wheel.

The three-phase AC electromotive force generated by the three-phase winding in the generator is rectified by the diode, and the direct current is output, which supplies power to the load and charges the battery.

The working bending principle of the alternator is as follows:

The electromagnetic induction principle of electric potential is induced by wire-cut magnetic field lines, and the mechanical energy of the prime mover is converted into electrical energy output. The synchronous generator consists of two parts: a stator and a rotor. The stator is the armature that emits electricity, and the rotor is the magnetic pole.

The stator is composed of an armature core, a uniformly discharged three-phase winding, a base and an end cover. The rotor is usually of the hidden pole type, which is composed of an excitation winding, an iron core and shaft, a retaining ring, a central ring, etc. A direct current is fed through the excitation windings of the rotor, which produces a nearly sinusoidally distributed magnetic field (called the rotor magnetic field), whose effective excitation flux intersects the stationary armature windings.

When the rotor rotates, the rotor magnetic field alarm wheel rotates with the same rotation and rotates once per revolution, and the magnetic field lines sequentially cut each phase winding of the stator, and the three-phase alternating current potential is induced in the three-phase stator winding. When the generator is operating with a symmetrical load, the three-phase armature current is combined to produce a rotating magnetic field with synchronous speed. The stator magnetic field and the rotor magnetic field interact to produce braking torque.

From steam turbines, water turbines, and gas turbines, the input mechanical torque overcomes the braking torque and works work.

Electricity is one of the most important sources of energy in modern society. The generator is a mechanical equipment that converts other forms of energy into electrical energy, which is driven by a water turbine, steam turbine, diesel engine or other power machinery, and converts the energy generated by water, air flow, fuel combustion or atomic nucleus fission into mechanical energy and transmits it to the generator, which then converts it into electrical energy. Generators have a wide range of uses in industrial and agricultural production, national defense, science and technology, and daily life.

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.

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 DC motor is equipped with a constant magnetic field, and after the current is passed through the stator coil, an electromagnetic force is generated, so it will move, but the direction of the current will be constantly changed, so a brush is generally used to contact the terminal. Therefore, the cost of construction is relatively high. Generally, it is used more in servo motors, speed motors and excitation motors.

The AC motor has only one winding, and the rotor is a squirrel cage. When the single-phase sinusoidal current passes through the stator winding, the motor will produce an alternating magnetic field, the strength and direction of this magnetic field change with time as a sinusoidal law, but it is fixed in the spatial orientation, so it is also called the alternating fluctuating magnetic field.

This alternating pulsating magnetic field can be decomposed into two rotating magnetic fields that are opposite to each other at the same speed and direction of rotation, and when the rotor is stationary, these two rotating magnetic fields produce two torques of equal magnitude and opposite directions in the rotor, so that the resultant torque is zero, so the motor cannot rotate.

First, the principle of power generation.

The basic principle on which an alternator generates alternating current is the principle of electromagnetic induction. When direct current is introduced into the rotor windings of the generator, a magnetic field is generated, and the rotor rotates under the drive of the engine, and the stator winding cuts the rotor magnetic field to induce three-phase AC electromotive force.

Second, the principle of rectification.

The rectifier circuit converts the three-phase electromotive force into a DC pulsating voltage; Because the battery has the function of 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, and the excitation of the generator has two ways: other excitation and self-excitation.

1) Other incentives.

When the speed of the generator is low (the engine does not reach the idle speed), it cannot generate electricity, and the battery needs to supply the current of the generator excitation winding, so that the excitation winding generates a magnetic field to generate electricity. This method of generating electricity by the excitation current supplied by the battery is called separately excited power generation.

2) Self-motivation.

With the increase of speed (generally when the engine reaches idle speed), the electromotive force of the generator stator winding gradually rises and can make the rectifier diode conductive, when the output voltage of the generator is greater than the battery voltage, the generator can supply power to the outside, at this time the electricity generated by itself can be supplied to the excitation winding, and the way of self-supply excitation current power generation is called self-excited power generation.

Operating characteristics of the alternator.

The working characteristics of the alternator refer to the relationship between the terminal voltage U, the output current i and the rotational speed n when the generator is working.

First, the no-load characteristics.

The no-load characteristic refers to the relationship between the voltage u at the generator end and the speed n when the generator is no-load (i.e., i 0).