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The difference between ordinary motor and frequency conversion motor

1. The difference between the structure of ordinary motor and variable frequency motor

1). Higher insulation level requirements

Generally, the insulation grade of frequency conversion motor is f grade or higher, and the insulation strength of ground insulation and wire turn is strengthened, especially the ability of insulation to withstand impulse voltage should be considered.

2. The vibration and noise requirements of the frequency conversion motor are higher

The frequency conversion motor must fully consider the rigidity of the motor components and the whole (public number: pump housekeeper), and try its best to increase its natural frequency to avoid resonance with each force wave.

3). Different cooling methods for frequency conversion motor

The frequency conversion motor generally adopts forced ventilation cooling, that is, the main motor cooling fan is driven by an independent motor.

4). Different protective measures

Bearing insulation measures should be adopted for frequency conversion motors with a capacity exceeding 160KW. The main reason is that the asymmetry of the magnetic circuit is likely to occur, and the shaft current will also be generated. When the currents generated by other high-frequency components are combined together, the shaft current will greatly increase, resulting in damage to the bearing, so insulation measures are generally taken. For constant power frequency conversion motors, when the speed exceeds 3000 / min, special high temperature resistant grease should be used to compensate for the increase in bearing temperature.

5). Different cooling system

The frequency conversion motor cooling fan is powered by an independent power supply to ensure continuous cooling capacity.

2. The difference between the design of ordinary motor and variable frequency motor

1). Electromagnetic design

For ordinary asynchronous motors, the main performance parameters considered in the design are overload capacity, starting performance, efficiency and power factor. The frequency conversion motor, because the critical slip ratio is inversely proportional to the power frequency, can be directly started when the critical slip ratio is close to 1, therefore, overload capacity and starting performance do not need to be considered too much, but the key problem to be solved is how to improve the motor The adaptability of non-sine wave power supply.

2). Structural design

In the structural design, it’s also necessary to consider the impact of the non-sinusoidal power supply characteristics on the insulation structure, vibration, and noise cooling method of the variable frequency motor.

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