The machine crashed after working for a while. What’s the reason? Does the frequency converter have a fault code? If yes, check the manual. Most of them are over-current and undervoltage. If it is normal, the friction of the air-cooled inverter equipment may be large and the resistance will be large. Adjust the over-current value a little more or the torque a little more. Do not adjust too much at once, depending on the rated current of the motor. Check whether the high-power equipment starts when the frequency converter stops, resulting in undervoltage.
Solution and cause analysis:
First, the deceleration time of the frequency converter is set too short. When the frequency converter drags a large load, its deceleration time is set too small. During the deceleration process, the output frequency of the frequency converter drops too fast, while the load inertia is large, which makes the actual speed of the motor higher than the speed corresponding to the output frequency of the frequency converter, making the motor in the power generation state, thus causing the DC link voltage in the middle of the frequency converter to be too high, reaching the limit value and tripping, Therefore, large frequency converters are generally equipped with overvoltage word processing units.
Second, when multiple motors drive the same load, because there is no load distribution, when the actual speed of one motor exceeds the timing speed of another motor, the high speed is equivalent to the prime mover, and the low speed is equivalent to the generator, which may also cause over-voltage fault.
Third, due to the capacitor life of the intermediate DC link of the frequency converter, after years of use, the capacitor capacity decreases, and the adjustment ability of the intermediate DC link to the DC voltage decreases, and the probability of overvoltage tripping increases. In practical application, the second factor is more. Take the converter of ladle trolley of rh refining furnace as an example. It is driven by two motors with the same load. Overvoltage alarm failures often occur during operation, and the same converter often alarms. Through observation, the voltage value of the intermediate DC link of the converter is high at high frequency during operation. Through analysis, the actual speed of one motor is higher than the actual speed of the other motor, making it work in the power generation state, And the intermediate DC link consumes this part of energy very well, which leads to the excessive voltage of the intermediate DC link of the frequency converter, and the over-voltage fault is reported.
Post time: Dec-06-2022