How does the variable frequency motor realize the variable frequency function?

Update:12 Oct 2020
Summary:

Do you know how the variable frequency motor realizes t […]

Do you know how the variable frequency motor realizes the variable frequency function? The variable frequency motor is first used for variable frequency speed regulation through the frequency converter. Inverter is output through AC-DC-AC input, and there are IGBT inside the inverter to adjust output voltage and frequency. The inverter has functions such as overload protection, overcurrent and overvoltage.

The frequency conversion motor is mainly the speed of the asynchronous motor. When the slip rate does not change much, the speed is proportional to the frequency, so the speed of the motor can be changed by changing the power frequency.

The frequency conversion system of the motor mostly adopts the constant V/F control method. His advantages are:

1. With start function;
2. Using electromagnetic design to reduce the resistance of stator and rotor;
3. Adapt to frequent speed changes under different working conditions;
4. Energy saving to a certain extent.

Different from ordinary motors, ordinary motors can only operate normally under rated conditions, and frequency conversion motors overcome vibration and overheating at low frequencies, so the performance of frequency conversion motors is better than ordinary motors.

Aspects that should be paid attention to in the design of high-power variable frequency motors

1. Higher insulation requirements
The insulation class of the high-power variable frequency motor is F or higher, strengthen the insulation to the ground and the insulation strength of the turns, and especially consider the ability of the insulation to withstand the impact voltage.

2. High-power variable frequency motors have higher requirements for vibration and noise
The frequency conversion motor must fully consider the rigidity of the motor components and the whole, and try to increase its natural frequency to avoid resonance with each force wave.

3. Strengthen the protection measures of variable frequency motors
For high-power frequency conversion motors with a capacity exceeding 160KW, bearing insulation measures are adopted. The main reason is that when the high-power variable frequency motor is running, it is easy to produce asymmetric magnetic circuit and also produce shaft current. When the currents generated by other high-frequency components work together, the shaft current will greatly increase, resulting in bearing damage. Optimized insulation measures.

For high-power variable frequency motors, when the speed exceeds 3000/min, special high-temperature-resistant grease should be used to compensate for the temperature rise of the bearing.

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