Analysis of Abnormal Causes in the Use of Frequency Converter

2021-05-04

Ⅰ. Abnormal power supply of frequency converter:

1. Power supply abnormalities can be roughly divided into the following three types, namely phase loss, low voltage, and power failure, and sometimes a mixed form of them also appears. The main reasons for these abnormal phenomena are mostly caused by wind, snow, and lightning strikes on transmission lines, and sometimes because of short-circuits to ground and interphase short circuits in the same power supply system. The lightning strikes vary greatly by region and season. In addition to voltage fluctuations, some power grids or self-generating units also have frequency fluctuations, and these phenomena sometimes recur in a short period of time. In order to ensure the normal operation of the equipment, corresponding requirements are also set for the power supply of the frequency converter.

2. If there are equipments such as electric motors and induction cookers that are directly started nearby, in order to prevent the voltage drop caused by the operation of these equipments, the power supply should be separated from the power supply of the frequency converter to reduce the mutual influence.

3. For equipment that requires continuous operation after instantaneous power failure, in addition to selecting a suitable price inverter, the speed reduction ratio of the motor load should also be considered in advance. When both the frequency converter and the external control loop adopt the instantaneous power failure compensation method, after the loss of voltage is restored, the speed of the speed measurement motor is used to prevent overcurrent during acceleration.

4. For equipment that requires continuous operation, the converter should be equipped with an automatic switching non-stop power supply device. For example, the frequency converter with diode input and single-phase control power supply can continue to work despite the lack of phase, but the current of individual components in the rectifier and the pulse current of the capacitor are too large. If it is operated for a long time, it will have a harmful effect on the life and reliability of the frequency converter, and should be checked and dealt with as soon as possible.

Ⅱ. Abnormality of the cooling system of frequency converter:

The cooling system of the frequency converter mainly includes heat sinks and cooling fans. The cooling fan has a short lifespan. When the service life is approaching, the fan vibrates, the noise increases and finally stops, and the frequency converter trips due to IPM overheating. The life of the cooling fan is limited by the bearing, which is about 10,000 to 35,000 h. When the frequency converter is running continuously, the fan or bearing needs to be replaced every 2 to 3 years. In order to extend the life of the fan, the fan of some products only runs when the frequency converter is running instead of when the power is turned on.