The characteristics and advantages of permanent magnet motors

Motor From the source of excitation can be divided into two categories: permanent magnet motor, and electric excitation motor. A permanent magnet motor is an electric motor that produces an excitation magnetic field from a permanent magnet. The most widely used three-phase asynchronous motors in industry and civil use, such as Y-Series, Y2-Series, YE2-Series, YX3 Series, Series YB, series YB2 series, etc. all belong to electric excitation motors. ENNENG Motor products are ultra-efficient permanent magnet synchronous motors.

Compared with traditional electric excitation motors, permanent magnet motors, especially rare earth permanent magnet motors, have the advantages of simple structure, reliable operation, small size, lightweight, small loss and high efficiency, and flexible and diverse shape and size of the motor. The application is extremely wide, covering almost all areas of aerospace, national defense, industrial and agricultural production, and daily life.

The permanent magnet synchronous motor has the following characteristics:

• Rated efficiency is 2% to 5% higher than normal asynchronous motors;
• The efficiency rises rapidly with the increase of the load. When the load changes within the range of 25% to 120%, it maintains high efficiency. The high-efficiency operating range is much higher than that of ordinary asynchronous motors. Light-load, variable-load, and full-load all have significant energy-saving effects;
• Power factors up to 0.95 and above, no reactive compensation required;
• The power factor is greatly improved. Compared with asynchronous motors, the running current is reduced by more than 10%. Due to the decrease in operating current and system losses, energy-saving effects of about 1% can be achieved.
• Low-temperature rise, high power density: 20K lower than three-phase asynchronous motor temperature rise, design temperature rise is the same and can be made into a smaller volume, saving more effective materials;
• High starting torque and high overload capacity: according to requirements, it can be designed with high starting torque (3-5 times) and high overload capacity;
• The variable frequency speed control system is used, which is better in dynamic response and better than that of asynchronous motors.
• The installation dimensions are the same as the asynchronous motors currently widely used, and the design and selection are very convenient.
• Due to the increase in power factor, the visual power of the power supply system transformer is greatly reduced, which improves the power supply capacity of the transformer, and can also greatly reduce the cost of the system cable (new project);
• When the new project is built, all the drive systems use permanent magnet synchronous motors, the project investment is basically the same as the use of asynchronous motors, and the project can continue to obtain energy-saving benefits after the project is put into operation;

In the general industrial sector, the replacement of low-voltage(380/660/1140V) high-efficiency asynchronous motors, the system saves 5% to 30% energy, and the high-voltage(6kV/10kV) high-efficiency asynchronous motors, system saves 2% to 10%.

Application:

Permanent magnet synchronous motors can be combined with frequency converters to form the best open-loop step-less speed control system, which has been widely used for speed control transmission equipment in petrochemical, chemical fiber, textile, machinery, electronics, glass, rubber, packaging, printing, paper making, printing and dyeing, metallurgy and other industries.

The rotor magnetic circuit structure of the permanent magnet synchronous motor is different, so the operation characteristics and control system of the motor are also different. According to the different positions of the permanent magnets on the rotor, permanent magnet synchronous motors can be mainly divided into the surface type and interior type. In the surface-type permanent magnet synchronous motor, the permanent magnets are usually tile-shaped and located on the outer surface of the rotor core. The important feature of this motor is that the main inductances of the straight and orthogonal axes are equal; the interior permanent magnet is located inside the rotor, and there is a pole piece made of ferromagnetic material between the outer surface of the permanent magnet and the inner circle of the stator core, which can protect the permanent magnet. The important feature of this permanent magnet motor is that the main inductances of the straight and quadrature axes are not equal. Therefore, the performance of these two motors is different.

A few small problems that are easily overlooked about the motor:

1. Why can't general motors be used in plateau areas?

Altitude has adverse effects on motor temperature rise, motor corona (high voltage motor) and commutation of DC motor. The following three aspects should be noted:

(1) The higher the altitude, the higher the temperature rise of the motor, the lower the output power. However, when the temperature decreases with the increase of altitude enough to compensate for the influence of altitude on the temperature rise, the rated output power of the motor can remain unchanged;

(2) Anti-corona measures should be taken when the high-voltage motor is used in the plateau;

(3) The altitude is not good for the commutation of the DC motor, so pay attention to the selection of carbon brush materials.

2. Why is the motor not suitable for light load operation?

When the motor runs at a light load, it will cause:

(1) The power factor of the motor is low;

(2) The motor efficiency is low.

(3) It will cause equipment waste and uneconomical operation.

3. Why can't the motor start in a cold environment?

Excessive use of the motor in a low-temperature environment will cause:

(1) Motor insulation cracks;

(2) Bearing grease freezes;

(3) The solder powder of the wire joint is powdered.

Therefore, the motor should be heated and stored in a cold environment, and the windings and bearings should be checked before running.

4. Why can't a 60Hz motor use a 50Hz power supply?

When the motor is designed, the silicon steel sheet generally works in the saturation region of the magnetization curve. When the power supply voltage is constant, reducing the frequency will increase the magnetic flux and the excitation current, resulting in an increase in the motor current and copper consumption, which will eventually lead to an increase in the temperature rise of the motor. In severe cases, the motor may be burned due to overheating of the coil.

5. Motor soft start

The soft start has a limited energy-saving effect, but it can reduce the impact of start-up on the power grid, and can also achieve smooth start to protect the motor unit. According to the theory of energy conservation, due to the addition of a relatively complex control circuit, soft start not only does not save energy, and also increases energy consumption. But it can reduce the starting current of the circuit and play a protective role.