The working principle of a permanent magnet generator

Like other types of rotating motors, permanent magnet synchronous generators consist of two parts: a fixed stator and a rotatable rotor. Due to the relative slashing activity between the windings and the main magnetic field, a three-dimensional symmetrical alternating potential of periodic magnitude and direction is induced in the windings. AC power is provided through the lead-outs.

Permanent magnet generator refers to a power generation device that converts mechanical energy from thermal energy into electrical energy. It was first developed by France. The biggest difference between a permanent magnet generator and an excitation generator is that its excitation field is generated by a permanent magnet.

Permanent magnets are both a magnetic source and an integral part of the magnetic circuit in a motor. The magnetic properties of permanent magnets are not only related to the manufacturing process of the production plant, but also related to the shape and size of the permanent magnet, the capacity of the magnetizer and the magnetization method, and the specific performance data is very discrete.

A specialized circuit is used to drive an electromagnet to generate a magnetic field.

The magnetic field strength is much stronger than that of a permanent magnet.

In the place of the permanent magnet, an electromagnet is first energized (from elsewhere), but then you can generate your own electricity, and then you can connect the coil on the electromagnet back to generate your own electricity.

The permanent magnet brushless DC motor is turned on and off by the power tube of the inverter according to a certain law, so that the stator armature of the motor generates a magnetic potential that continuously advances according to the electric angle of 60°, and drives the rotor of the motor to rotate.

It can be seen that the magnetic potential generated by the stator armature will be turned on and off regularly with the power tube, and will continue to rotate clockwise at an electrical angle of 60°. There are six starting combinations of inverter power tubes, each of which can only produce the maximum average electromagnetic torque if it corresponds to a defined rotor position or generator waveform.

When the angle between the two magnetic potential vectors is 90°, the interaction force is maximum. The magnetic potential generated by the electron armature advances at a 60° electrical angle, so the angle between the rotor and stator magnetic potential varies between 60° and 120° in each starting mode to produce the maximum average electromagnetic torque.

The structural permanent magnet brushless motor can be regarded as a DC motor that replaces mechanical commutation with an electronic commutation device, which is mainly composed of a synchronous motor body, a power electronic inverter, a rotor position detector and a controller. Among them, the rotor of the synchronous motor is mainly composed of permanent magnets and magnets.

The permanent magnet brushless DC motor is mainly composed of the permanent magnet motor body, the rotor position sensor and the electronic commutation circuit. Whether it is the structure or the control method, the permanent magnet brushless DC motor has many similarities with the traditional DC motor: the stator pole of the brushed DC motor is replaced by a rotor equipped with a permanent magnet; replacing the armature with a stator with multiphase windings; Replace mechanical commutators and brushes with electronic commutators consisting of solid-state inverters and shaft position detectors.

Basic structure of permanent magnet brushless DC motor:

The permanent magnet brushless DC motor developed on the basis of the traditional DC motor is basically the same in structure, the difference is that the armature winding of the permanent magnet brushless DC motor is placed on the stator, which is similar to the winding of the AC motor, and at the same time, it generally adopts the form of multiphase, of which the three are used the most in the current situation; The rotor is a permanent magnet and adopts electronic commutation, and the interaction between the stator magnetic field and the rotor permanent magnetic field generates electromagnetic torque. According to the shape of the permanent magnet and the different magnetic circuit structure, the permanent magnet brushless DC motor has three kinds of air gap magnetic field waveforms: square wave, trapezoidal wave and sine wave, and the waveform of the back EMF corresponds to the same. Generally, motors with a back EMF that is a sine wave are called permanent magnet synchronous motors.

If the waveform is the other two types, it is called a permanent magnet brushless DC motor.

Composition of permanent magnet brushless DC motor:

It is mainly composed of three parts. The rotor is available in two types: salient pole type and inline type, and is made of permanent magnet material. The armature on the stator is the opposite of a permanent magnet brushed DC motor, so it has a rotating magnetic field and a fixed armature.

Working principle of permanent magnet brushless DC motor:

In order to better illustrate the working principle of the permanent magnet brushless DC motor, the permanent magnet brushless DC motor driven by three-phase star-shaped full-bridge drive for electric vehicles was analyzed, and its forward and reverse working conditions were studied. The main circuit of the motor control system is shown in Figure 1.

Figure 1: Circuit diagram of a full-bridge drive of a permanent magnet brushless DC motor.

When the rotor of the motor is in the position shown in Figure 2(a), the signal from the position sensor is logically transformed through the control system, and the output control signal makes the A and B phase windings of the motor conduct, and the current flows in from phase A and phase B out, and generates electromagnetic torque to rotate the motor in a clockwise direction; Using the 60° electrical angle as the reference, it is easy to see the conduction of the motor winding when the motor rotor reaches the position shown in Figure 9(b). When the sequence of the conduction phase of the winding is ab-ac-bc-ba-ca-cb-ab, the motor rotates in the clockwise direction. Similarly, when the current passes through phases b and c at the position shown in Figure 9(a), the resulting electromagnetic torque will cause the motor to rotate in the opposite direction, and when the armature winding of the motor is in the turn-on sequence of bc-ac-ab-cb-ca-ba-bc, the motor will rotate in the counterclockwise direction.

Therefore, to achieve clockwise or counterclockwise rotation of the motor, it is only necessary to change the logical sequence of motor conduction.

The magnetic field of an ordinary DC motor is used as a stator to energize the rotor, so the rotor must be energized with a brush. The brushless DC motor is just the opposite, the stator is made into a coil, and the rotor is made into a permanent magnet, which attracts the rotor permanent magnet to rotate by the stator magnetic field, so there is no need to energize the rotor, and there is no need for carbon brushes.

During phase commutation, the rotor position is detected, and the direction of the stator magnetic field is changed according to the position of the rotor permanent magnet through electronic commutation.

The carbon brush is eliminated, which has high efficiency, long life, high power-to-volume ratio and low noise. However, the permanent magnet is made of rare earth alloys, which is more expensive and requires additional electronic commutator control, so the cost is higher than that of DC motors.

Permanent magnet brushless DC motors should be noted in the application:

1) If the product is not specifically specified, under normal circumstances (such as Alnico permanent magnet DC motor or ferrite permanent magnet DC motor) permanent magnet DC motor is not allowed to reverse braking operation under the rated voltage, otherwise it will cause demagnetization of the permanent magnet; If it is necessary to operate in this way, a current-limiting resistor should be added to limit the excessive current.

2) Follow the steps below to conduct a preliminary inspection of the quality of the motor:

First of all, check the appearance of the motor: there should be no scratches, bruises and the coating layer should fall off; Then rotate the shaft, which should be able to rotate flexibly without obvious jamming. Check whether the wiring of the motor is firm and run with electricity.

There should be no friction in the process of rotation of the motor, the most prominent of which is bearing friction. After the bearing is worn, it will make abnormal sounds, and the phenomenon of local overheating and temperature rise will occur.

3) Pay attention to the demagnetization of the permanent magnet caused by excessive current, temperature change and open magnetic circuit during disassembly and assembly, especially for alnico permanent magnet motors, the permanent magnet magnetic circuit should be protected by magnetic short circuit when disassembling and assembling, otherwise it should be magnetized after demagnetization.

The permanent magnet n-s alternately exchange, so that the position sensor produces a phase difference of 120 ° U, V, W square waves, combined with the forward and reverse signals to produce an effective six-state coding signal, through the logic component processing to produce T1-T4 on, T1-T6 on, T3-T6 on, T3-T2 on, T5-T2 on, T5-T4 on, that is to say, the DC bus voltage is added on a + b-, a + c-, b + c-, b + a-, c + a-, c + b-, c + b-, c+b-, In this way, every time the rotor turns a pair of N-S poles, the T1-T6 power tube is turned on in turn according to the fixed combination into six states. In each state, only the two-phase winding is energized, and a state is changed sequentially, the magnetic field axis generated by the stator winding rotates 60 ° electrical angle in space, and the rotor follows the stator magnetic field rotation equivalent to the 60 ° electrical angle space position, and the rotor is in a new position, so that the position sensor U, V, W produce a new set of codes as agreed, and the new code changes the conduction combination of the power tube, so that the magnetic field shaft produced by the stator winding advances the 60 ° electric angle again, and so on, the force Hui permanent magnet brushless DC motor will produce continuous torque, Drag the load for continuous rotation.

Features of permanent magnet brushless DC motor.

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So today, the car will give friends a brief introduction to the permanent magnet generator!

What is a Permanent Magnet Generator&mdash&mdash Introduction.

In today's DC motors, the excitation of the main pole magnetic field caused by the DC current is called current excitation. If a permanent magnet is used instead of an electric current to excite the main pole magnetic field, such a motor is called a permanent magnet motor.

What is the Permanent Magnet Generator &mdash&mdash Advantages.

1.The structure is simple and the reliability is high. The present invention omits the excitation winding, carbon brush and slip ring structure of excitation generator, the overall structure is simple, prevents the excitation winding from being easily burned out, the carbon brush and the slip ring standby structure is simple, the overall structure is simple and delayed, the excitation winding of the excitation generator is easy to burn out, and the carbon brush and slip ring are easy to wear out, and the reliability is greatly improved.

2.Small size, light weight, high specific power. After the permanent magnet junction code rolling structure, the internal structure design of the generator is very compact, and the volume and weight are greatly shortened.

The simplification of the permanent magnet rotor structure also shortens the inertia of the rotor, increases the useful rotational speed, and achieves a higher specific power (i.e., power-to-volume ratio). 3.Good power generation performance at medium and low speeds.

In the case of similar power levels, the output power of the permanent magnet generator needs to be twice that of the excitation generator at no load, so the actual excitation generator of the permanent magnet generator has the same power level.

What is a permanent magnet generator &mdash&mdash to take care of your health.

There are many cases where generators break down frequently, and the key is that the usual maintenance is not in place or is not repaired immediately. There is no difference between an engine and a car, so we need to develop good maintenance habits. Immediately do it according to the specifications and treat the generator as your own car.

The above is a brief introduction to the permanent magnet generator in the car. How about the introduction of permanent magnet generators? The car briefly introduced three aspects for friends, namely the introduction, advantages and maintenance methods of permanent magnet generators.

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What is a permanent magnet machine in a generator? What role does it play?

What is a permanent magnet machine in a generator? What role does it play? Hello dear!

Glad to answer for you!! The permanent magnet generator is located in the head part of the generator set, which rotates synchronously with the generator set. Its function is mainly to provide signal power supply for the speed control system of the turbine to collect the frequency of the unit (in addition to this signal power supply, the general unit speed control system also obtains the signal through the voltage transformer at the outlet of the generator) and to supply power to the speed relay of the unit.

In the past, permanent magnet machines mostly used three-phase salient pole type, that is, permanent magnets were used as magnetic poles to rotate, and the volume was very large. The single-phase induction sub-type permanent magnet machine that is widely used is very small in size. Recently, some power plants have replaced permanent magnet machines with a gear disc tachymeter device mounted on a large shaft with bright lead.

The units of the new power plant have a tendency to cancel the Yongxiang Zheng magnetic machine. 。I hope mine is helpful to you and I wish you a happy life.

Summary. Kiss hello, <>

Yes, it has the advantages of high efficiency, high power density and low noise, so it performs well in some applications. Compared with traditional induction motors, permanent magnet motors have higher rotational speed and better control performance. In addition, permanent magnet motors can be adjusted for torque and speed by varying the current and magnetic field, making them suitable for different applications.

Can permanent magnet generators be used as motors?

Hello, can the generator with a diesel engine be used as a motor?

Kiss hello, <>

Yes, it has the advantages of high efficiency, high power density and low noise, so it has shown great performance in some applications. Compared with traditional induction motors, permanent magnet motors have higher speed and better control performance. In addition, permanent magnet motors can be adjusted by changing the current and magnetic field to adjust the torque and speed section, making them suitable for different applications.

That is, you don't need to modify it, you can use it directly by connecting it to three-phase electricity, right?

I'm just trying to make sure that it doesn't cause unnecessary destruction.

Hello, the generator with the diesel engine can also be used as an electric motor without the need to generate electricity. You only need to connect the power supply to the output port of the generator, and then control the speed and direction of the generator through the controller or other circuits, and let it run as a motor.

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There are a few things to be aware of. First of all, it is necessary to ensure that the voltage and frequency of the generator match the power source used, otherwise it will cause damage to the liquid creature of the equipment. Secondly, pay attention to the rated power and speed of the generator to avoid the generator burning out due to overload.

I have a three-phase electric system, and I don't have speed control, I have to adjust the speed by changing the pulley.

May I ask if this method is possible, if it can, then it will be good.

Hello dear, this should be based on your machine specifications, power matching, find professionals to install.

Okay, thank you, I'll just plug it in and see the speed when the time comes, thank you for the answer, goodbye.

Kiss, depending on the specific parameters, safety first.