What is the difference between a brushless DC motor and a vector sine wave permanent magnet brushles

Brushless DC motor.

It is a type of motor, while vector sine wave is the control method, and permanent magnet brushless motor is one of the brushless DC motors.

First of all, let's understand the concept of these two types of motors.

Brushless DC motors use electronic commutation (also known as electronic rotor) to replace the traditional mechanical commutation, thus avoiding mechanical loss and electrical sparks. Its structure is relatively simple and it is relatively easy to maintain, so it has a wide range of applications in many fields.

The vector sine wave permanent magnet brushless motor is a more advanced motor, which uses sine wave current control technology. This technology results in a smoother torque output from the motor, more efficient, and less noisy. In addition, due to its higher control accuracy, it can better adapt to various complex application scenarios.

For electric four-wheeled scooters, if you pursue higher performance and comfort, then choosing a vector sine wave permanent magnet brushless motor is a better choice. This is because the motor provides a more stable and powerful power output, and is less noisy during operation and more comfortable to drive.

However, brushless DC motors also have their advantages. Its structure is simple, it is relatively easy to maintain, and it is relatively low. Therefore, if you have a limited budget, or the performance requirements are not particularly high, then choosing a brushless DC motor is also a good choice.

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.

The main advantages of permanent magnet brushless DC motors compared with ordinary brushless motors:

1. Compared with the traditional motor, any speed point can save electric energy, especially when the speed is low, this advantage of the first key is particularly obvious. Most modern submarines use large-diameter, low-speed, 7-blade, large-side-oblique spiral cavern or pump-jet propeller, which has low speed and high propulsion efficiency. Moreover, submarines mostly maneuver at low-noise speeds underwater, which makes this advantage of permanent magnet motors better reflected and rented.

Second, the size is small, light weight, the structure of the permanent magnet motor is simple, due to the use of high-performance permanent magnet data to provide the magnetic field, so that the air gap magnetic field of the permanent magnet motor is greatly enhanced than the general motor, and the volume of the permanent magnet motor and the general motor are greatly reduced, and the size and shape of the motor are also flexible and diverse.

Third, the failure rate is lower and widely used, due to the use of high-performance rare earth permanent magnet data to provide magnetic field, the failure rate is lower, and the use is more and more widespread.

Fourth, the starting torque is large, because the rotor winding does not work when the permanent magnet motor is operating normally, so the rotor winding can meet the requirements of high starting torque in the design, such as from multiple to double, or even larger.

This kind of motor can replace the original Y, Y2, Y3 and other motors with the same size in use. Reduces the hassle of the replacement process. Compared with ordinary motors, the permanent magnet electric Zen key rolling machine has its own characteristics.

The pole speed is 1400N min multi-revolution, and the permanent magnet synchronous motor speed is 1500N minOther speed motors, roughly like this. High power factor.

When the permanent magnet motor is running normally, the rotor speed is the same as the stator magnetic field speed, there is no current on the rotor squirrel cage, and the induced current on the stator decreases, so the bright hole power factor is high. Through reasonable design, it can be made to work in the hysteresis power factor, unit power factor and leading power factor. Generally, the hysteresis power factor can be reached and exceeded, and a large number of permanent magnet motors can be used to save equipment such as reactive power compensators.

High efficiency, especially high operational efficiency. When the permanent magnet motor is running normally, because there is a permanent magnet on the rotor - NdFeB magnet, the normal operation of the motor can be guaranteed by the magnetic field of the permanent magnet, so the rotor squirrel cage has no current, and there is no winding loss.

Permanent magnet DC motor is divided into permanent magnet DC brushless motor and permanent magnet DC brush motor according to whether there is a brush, as the name suggests, the brush motor is a DC motor containing brushes, on the contrary, it is a brushless motor, and the range of applications of the two motors is very wide, so the difference between brushless motor and brush motor is **? Let's take a look at the lack of fronts

1. Differences in principle

The brushed motor is a motor that contains a brush device to convert electrical energy into mechanical energy or convert mechanical energy into electrical energy, which is different from brushless motors, which remove brushes and are an integrated product composed of motor body and driver.

2. Structural differences

The structure of brushless motor and brushed motor is just opposite, the rotor of the brushed motor is the coil winding, the stator is the permanent magnet steel, the rotor of the brushless motor is the permanent magnet steel, and the stator is the coil winding.

3. Scope of use

Brushed motors are usually used in ordinary equipment, and brushless motors are mainly used in high-precision equipment.

4. Working life

In the case of continuous work of the brush motor and the brushless motor at the same time, the working life of the brush motor is about several hundred hours, and the life of the brushless motor can reach tens of thousands of hours when the bearing is selected well.

5. Noise level

The brushed motor has the noise generated by the wear of the brush, and the brushless motor has no brush, which runs smoothly and the friction is greatly reduced, and the noise is relatively low and there are many socks.

6. Efficiency transformation

The efficiency conversion of brushless motors is about 90%, and the efficiency of brushed motors can only reach about 70%.

Because the output power of the brush motor is small, and the heat is large, most of the electric energy is converted into heat energy, so the output power is small and the efficiency is low.

7. The cost is high

The manufacturing cost of brushed motors is lower than that of brushless motors.

The above is the difference between permanent magnet brushless DC motor and brushed motor, I hope it can help you

First, the composition is different.

1. The brush of the permanent magnet DC motor is mainly composed of the stator and the rotor, the carbon brush hand search and other parts, the stator has a magnetic pole (winding type or permanent magnet type), and the rotor has a winding.

2. The brushless permanent magnet DC motor is mainly composed of stator and rotor and other parts, and there is no carbon brush.

Second, the working principle is different.

1. After the permanent magnet DC motor is energized, a magnetic field is also formed on the rotor, and there is an angle between the stator and the magnetic pole of the rotor, so that the motor rotates under the mutual attraction of the magnetic field of the stator and rotor. By changing the position of the brushes, you can change the direction of the angle between the magnetic poles of the stator and rotor, and thus the direction of rotation of the motor.

2. The brushless permanent magnet DC motor is mainly electronically commutated by the brushless motor, the coil does not move, and the magnetic pole rotates. Through the Hall element, the position of the poles of the permanent magnet is sensed, and according to this perception, the direction of the current in the coil is switched at the right time using an electronic circuit to ensure that the magnetic force in the correct direction is generated to drive the motor.

Third, the advantages are different.

1. The DC brush motor has fast starting response speed, large starting torque, stable speed change, almost no vibration is felt at the speed from zero to maximum, and it can drive a larger load when starting.

2. The starting resistance of the brushless motor is large (inductive reactance), so the power factor is small, the starting torque is relatively small, there is a buzzing sound when starting, and it is accompanied by strong vibration, and the driving load is small when starting.

Encyclopedia - Brushed DC motor.

Encyclopedia - Brushless DC motor.