Zhejiang Shuyi Electric Co. Ltd

11. When the IGBT is connected through, the dead time becomes narrower (the temperature increases, the inverter tube is aging), and the inverter tube enters the amplifying area (the drive power voltage drops, and the inverter tube ages).

12. The output current of the inverter determines the output torque of the inverter. If it is a constant torque load, the current has nothing to do with the frequency drop. The DC part of the inverter will decrease as the frequency decreases, and the input current will decrease as the frequency decreases.

13. The inverter plus the output reactor can effectively suppress the change of DU/DT, because the inverter output is all PWM wave, and there is also distributed capacitance at a long distance, so there may be a large leakage current.

14. Adding capacitors can’t change the power factor of the motor. It just means that the capacitor can provide part of the reactive current to the motor without the need for the motor to obtain it from the circuit.

15. Lowering the carrier frequency can also reduce interference.

16. Bias frequency and frequency gain: For example: the original is 0-10V, but now it becomes 0-5V, so it can be said that the bias frequency is -12.5HZ, and the frequency gain is 225%.

17. What is the reason for the overcurrent protection when the frequency conversion is light load: Usually, after the VF curve is set, it runs under heavy load. When it is under light load, there will be overcompensation, which is easy to magnetic saturation, so that the excitation current will be reduced. Distortion will occur.

18. During variable frequency operation, the speed can be slightly higher than the speed of the motor at power frequency.

19. When the VF curve is increased, the effective torque of the inverter can be increased.

20. In closed-loop control: if the proportional gain (used to amplify the difference between the target signal and the feedback signal) is too large, the frequency change will be too sensitive, so due to the mechanical inertia, overshoot will occur, and conversely, the frequency will drop in the same way, which is prone to occur. fluctuation. The solution to this is to use the integral link, and the introduction of the integral time is to make this change fluctuate within the range. Differential control is to give a pre-judgment value and let the target value move first, which solves the phenomenon that the integration time is too long and the action is slow.

21. When the ambient temperature is too high, it will affect the dead time of the IGBT module and narrow the dead time.


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