How to distinguish between ordinary motor and variable frequency motor?

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

1. Higher insulation level requirements

Generally, the insulation grade of the variable frequency motor is F or higher, which strengthens the insulation to the ground and the insulation strength of the wire turns, especially considering the ability of the insulation to withstand the impact voltage.

2. The vibration and noise requirements of variable frequency motors are higher

The frequency conversion motor should fully consider the rigidity of the motor components and the whole, and try to improve its natural frequency to avoid resonance with each force wave.

3. Variable frequency motor cooling method is different

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

4. Protection measures require different

Bearing insulation measures shall be adopted for variable frequency motors with capacity exceeding 160kW. Mainly easy to produce magnetic circuit asymmetry, will also produce shaft current, when other high-frequency components generated by the current combined action, the shaft current will be greatly increased, resulting in bearing damage, so generally to take insulation measures. For constant power variable frequency motor, when the speed exceeds 3000 m/min, special high temperature resistant grease should be used to compensate for the temperature rise of the bearing.

5. Different heat dissipation systems

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

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

1, Electromagnetic Design

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

2. Structural design

In the structural design, the influence of non-sinusoidal power supply characteristics on the insulation structure, vibration and noise cooling mode of the variable frequency motor is mainly considered.