Briefly describe the working principle of motor?

Motor is a kind of rotating motor, which converts electric energy into mechanical energy. It mainly includes electromagnetic winding or distributed stator winding and rotating armature or rotor for generating magnetic field. Under the action of the rotating magnetic field of the stator winding, current passes through the effective edge of the stator winding and is rotated by the magnetic field.

According to the principle of motor reversibility, if the structure of the motor is unchanged, the motor can be used as both a motor and a generator. This is a machine that converts electric energy into mechanical energy. Usually, the working part of the motor rotates, which is called rotor motor; There is also linear motion, called linear motor.

The motor can provide all kinds of power from milliwatts to kilowatts. Machine tools and water pumps need motor drive; Electric locomotives and elevators need motor traction. Electric fans, refrigerators, washing machines and even various motor toys in family life are inseparable from motors. Electric motors have been used in all aspects of modern social life.

The working principle of the motor: the electrified wire is stressed in the magnetic field.

With the intensification of competition in the motor manufacturing industry, mergers, acquisitions and capital operations among large motor manufacturing enterprises are becoming more and more frequent. Excellent motor manufacturing enterprises at home and abroad pay more and more attention to the research on the industry market, especially the in-depth study on the development environment of enterprises and the changes of customer demand trends. Because of this, a large number of excellent motor brands at home and abroad have risen rapidly and gradually become the leader in the motor manufacturing industry.

Motor itself is a labor-intensive product, unless it reaches a certain output scale, it is difficult to generate benefits, so the industry profit is very meager. There are about 300,000 employees in the automobile industry in China, and the profit of the industry in 2003 was only 280 million yuan. It is understood that even some enterprises with better benefits had a net profit of less than 5% last year. ?

At the same time, due to the poor production technology of most small enterprises, there are still a large number of unqualified products in the motor industry. According to the survey, the average loss of waste products, defective products and repaired products in China's motor enterprises is about 10%, while the unqualified level of motor enterprises in developed countries abroad is generally 0.3%.

In recent years, a number of enterprises with large output scale, good product level and quality and advanced technology and equipment have emerged in China's motor industry. However, no product share can dominate the domestic market. Small and medium-sized motors have not yet formed an internationally influential brand.

The motor industry is in urgent need of re-integration and survival of the fittest, which has become the development trend of the motor industry. Experts pointed out that although the motor industry is an old traditional industry, supporting motors in all walks of life are indispensable. Moreover, some larger motor enterprises occupy a large area and have good locations. After the merger, it will bring very rich income and financial resources to the acquirer.

Extended data

Motor starting methods include: full-voltage direct starting, autotransformer decompression starting, y-δ starting, soft starter and frequency converter.

Full pressure direct starting:

Under the condition that the capacity and load of power grid allow full voltage direct starting, full voltage direct starting can be considered. Its advantages are convenient operation and control, simple maintenance and relative economy. Mainly used for starting low-power motors. From the point of view of saving electric energy, this method is not suitable for motors larger than 1 1kw.

Automatic coupling decompression start:

Multi-tap step-down of autotransformer can not only meet the needs of starting different loads, but also obtain larger starting torque, which is a common step-down starting method for starting large-capacity motors. Its biggest advantage is large starting torque. When the winding tap is 80%, the starting torque can reach 64% of the direct starting. Starting torque can be adjusted by tap. It is still widely used today.

Start:

For squirrel-cage asynchronous motors with triangular stator windings in normal operation, if the stator windings are star-shaped when starting and triangular after starting, the starting current can be reduced and the impact on the power grid can be alleviated. This starting mode is called star delta decompression starting, or simply star delta starting (y-δ starting).

When star-shaped triangle is used for starting, the starting current is only 1/3 of that of the original triangle connection. If the starting current of direct starting is 6 ~ 7IE, the starting current is only 2 ~ 2.3 times that of star delta starting. That is to say, when the star triangle is used for starting, the starting torque is also reduced to 1/3 of the original triangle connection direct starting. Suitable for no-load or light-load starting occasions.

And compared with any other decompression starter, it has the simplest structure and the cheapest price. In addition, the star-delta starting mode has another advantage, that is, when the load is light, the motor can run in star connection. At this time, the rated torque can match the load, which can improve the efficiency of the motor and save power consumption.

Soft starter:

This is based on the phase-shifting voltage regulation principle of silicon controlled rectifier to realize the voltage regulation starting of motor, which is mainly used for the starting control of motor, with good starting effect but high cost.

Because of the use of thyristor, the harmonic interference of thyristor is large, which has a certain impact on the power grid. In addition, the fluctuation of power grid will also affect the conduction of SCR devices, especially when there are multiple SCR devices in the same power grid. Therefore, the failure rate of thyristor is high, because it involves power electronics technology, so the requirements for maintenance technicians are also high.

Frequency converter:

Inverter is the motor control device with the highest technical content, the most complete control function and the best control effect in the field of modern motor control. It adjusts the speed and torque of the motor by changing the frequency of the power grid. Because it involves power electronics technology and microcomputer technology, it has high cost and high requirements for maintenance technicians, so it is mainly used in fields that need speed regulation and high requirements for speed control.

References:

Baidu electric encyclopedia