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Home > Industry Information > Permanent magnet motor save power _Permanent magnet motor energy-saving What is the reason

Permanent magnet motor save power _Permanent magnet motor energy-saving What is the reason

2019-10-22

The Permanent Magnet Motor uses permanent magnets to generate the magnetic field of the motor. It does not require excitation coils or excitation currents. It has high efficiency and simple structure. It is a very good energy-saving motor. With the development of high-energy permanent magnets, permanent magnet motors have been widely used. This article first introduced the structure and working principle of the permanent magnet motor, followed by the advantages of the permanent magnet motor, and finally introduced the permanent magnet motor power saving? What are the reasons for permanent magnet motor power saving and the development trend of permanent magnet motors?

The structure and working principle of permanent magnet motor

In terms of structure

The motor is based on a magnetic field as an electromagnetic device for the conversion of mechanical energy and electrical energy. In the motion mechanism, first the air gap magnetic field energy conversion requires the air gap magnetic field generated by the permanent magnet, and secondly, the group enters the motor winding current, but this requires two special windings and corresponding devices, and provides energy to maintain the current The flow, the overall motor consists of two parts, the stator and the rotor. When the motor is in operation, the fixed part is called the stator, the stator is mainly punched by silicon steel, and the three-phase symmetrical distribution of the windings fixes the core chassis and bonnet parts, such as the rotor permanent magnet yoke and the shaft. The permanent magnet yoke, considering that the yoke is cylindrical, forms a permanent magnet motor on the rotating shaft.

In principle

The magnetic field interaction between the stator and the rotor generates two electromagnetic forces acting perpendicular to each other in the plane, thereby achieving the movement of the motor, and the electromagnetic thrust is the result of the interaction of the magnetic field generated by the permanent magnet array and the current in the coil array. When the electromagnetic torque overcomes the inertia of the rotor itself, as well as the damping torque generated by the magnet of the permanent magnet motor rotor rotor, the motor begins to move.

Permanent magnet motor save power _Permanent magnet motor energy saving What is the reason

Permanent magnet motor advantages

(1) High efficiency, environmental protection and energy saving

Permanent magnet motors are highly efficient and energy-saving products. Compared with induction motors, permanent magnet motors do not require reactive excitation currents, so they can greatly increase power factor. According to a large number of statistical calculations, the efficiency of permanent magnet motors is improved by 2% to 8% compared with the same specifications of heat engines. It is also possible to use smaller-capacity permanent magnet motors instead of larger-capacity induction motors, which solves the problem of energy waste. . Long-term use of this product can achieve the purpose of environmental protection and energy conservation.

(2) High performance

High-efficiency is also the obvious advantage of permanent magnet motors. Some performance indicators are beyond the reach of traditional standard motors. In some organizations, the speed ratio can be as high as 1:10000, and the speed control accuracy can reach 0.1%.

(3) Various types of structures with a great range of applications

Because the rotor structure is diverse, many varieties of permanent magnet motors have different characteristics and performances, from everyday life to aerospace, from simple power tools to high-tech products.

(4) Excellent control performance

Due to the high performance of rare earth permanent magnet materials, the torque constant, torque inertia ratio, power density, etc. of the motor are greatly improved. Through reasonable design, the inertial moment, electrical and mechanical time constants can be greatly reduced, and the main index of servo control performance has been greatly improved.

In modern permanent magnet motors, the design of the permanent magnet magnetic circuit has been relatively perfect, and the coercive force of the rare earth permanent magnet material is high, so the ability of the permanent magnet motor to resist armature reaction and other demagnetization is greatly enhanced, and the control parameters of the motor are greatly enhanced. With the external disturbances greatly reduced.

Since the permanent magnetic material is used instead of the electric excitation, the design of the excitation winding and the excitation magnetic field is reduced, thereby reducing the excitation magnetic flux, the excitation winding inductance, the excitation current and many other parameters, thereby directly reducing the controllable variables or parameters.

Permanent magnet motor save power _Permanent magnet motor energy saving What is the reason

Permanent magnet motor power saving

In theory, it is more power-efficient.

Permanent magnet motors have "three highs" compared with ordinary motors, high efficiency, high power factor, and high starting torque. The first two “highs” have shown that it is more energy-efficient than the average motor. In addition, the permanent magnet (synchronous) motor achieves the purpose of high starting torque of other synchronous motors, there is no rotor winding, no need to excite the rotor. It also reduces energy consumption.

What is the reason for saving power in permanent magnet motors?

When the permanent magnet motor's three-phase stator windings (with a phase difference of 120° electrical angle) lead to a three-phase alternating current with frequency f, it will generate a rotating magnetic field that moves at a synchronous speed.

In the steady state, the main pole magnetic field rotates synchronously with the rotating magnetic field, so the rotor speed is also the synchronous rotation speed. The stator rotating magnetic field and the permanent magnetic field established by the permanent magnet remain relatively stationary, and they interact and generate electromagnetic torque. The drive motor rotates and performs energy conversion.

Permanent magnet motor save power _Permanent magnet motor energy saving What is the reason

Permanent-magnet variable-frequency air compressor adopts high-efficiency permanent-magnet motor + frequency converter (PM motor). Screw-master and high-efficiency permanent magnet motor share the same main shaft. The motor has no bearing. The rotor with permanent magnet is directly installed on the protruding shaft of the male rotor. On the transmission efficiency 100%. This structure eliminates the point of failure of conventional motor bearings and enables motor-free maintenance.

The rare earth permanent magnetic material has excellent magnetic properties. After being magnetized, it no longer needs external energy to build a strong permanent magnetic field, which is used to replace the electric excitation magnetic field of the conventional motor. The high efficiency permanent magnet frequency conversion motor is not only highly efficient but also has a simple structure. , reliable operation, but also to achieve small size and light weight. It can not only achieve the high performance (such as special high efficiency, special high speed, high response speed) that can not be compared with the traditional electric excitation motor, but also can be made into special motors that can meet specific operation requirements, such as elevator traction motors, automobile special motors, etc. .

The combination of rare earth high-efficiency permanent-magnet motors and power electronics and microcomputer control technologies has brought the performance of motors and drive systems to a whole new level:

High-efficiency permanent-magnet variable-frequency motor maintains high efficiency under any load, saving more than 38% energy compared with ordinary motors, and saving more than 10% over induction-type variable-frequency motors.

The superior performance that can be started immediately after the motor stops, infinitely starts and stops without affecting the motor life, and the starting current does not exceed 100% full-load current.

Because the permanent magnet frequency conversion motor has the advantage of low speed and high output torque, its variable frequency control mode is more widely used for common induction variable frequency motors. The permanent magnet frequency conversion motor is 30% smaller than the same power motor, 35% lighter, and easier to maintain. In order to improve the performance and level of the supporting technical equipment, it is an important development direction for the motor industry to adjust the industrial structure.

At present, high-efficiency permanent magnet frequency conversion motor is the best choice for screw air compressor drive motor. It is more efficient and energy-saving than ordinary three-phase asynchronous frequency conversion motor.

Permanent magnet motor save power _Permanent magnet motor energy saving What is the reason

Permanent magnet motor development trend

As the foundation of many high-tech and high-tech industries, the combination of permanent magnet motors and microelectronics control technologies and power electronics technology can create many new types of mechatronic products with excellent performance. The permanent magnet motor serves as the basis and represents the typical development direction of the motor in the 21st century.

(1) Direction of development of the motor

Motor-driven loads, such as the use of general-purpose motors, are technically and economically unreasonable in some cases. For example, special motors are specially designed according to different load characteristics, such as rare earth permanent magnet motors with an energy saving rate as high as 20% for oil field pumping units. On the basis of specialization, the energy-saving potential of special motors is large. This also poses higher requirements for motor workers: they must not only study the motor itself, but also study the characteristics of the drive load, and design rare earth permanent magnet products with reasonable prices, reliable operation, and advanced performance.

(2) Development in the direction of lightweighting

Portable optical and electromechanical products. Permanent magnet motors have good control performance, energy saving and small size, can be adjusted by frequency changes, and are easy to make low-speed direct drive, etc., so in the medical devices, audio-visual products, computers, CNC machine tools, electric vehicles, aerospace products, etc. The field is widely used. In the future, with the development of control technology and electronic technology, the development of permanent magnet motor technology will become increasingly perfect.

(3) The development of high performance

The motor of modern equipment has a variety of high-performance, mobile equipment and other automation equipment use and motor servo system, chemical fiber equipment, frequency control synchronous motor speed, high precision, robot and rare earth permanent magnet servo motor ratio is high, and so on.

(4) Mechatronics

The foundation of mechatronics is the development of a variety of electromechanical integrated high-performance permanent magnet motors, such as CNC machine tools servo motors, the use of computer VCM voice coil motor, frequency control of rare earth permanent magnet motor and brushless DC motor It is the foundation of mechatronics.

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