During the operation of the motor, the operating current exceeds the rated value, which is called overload.
Overload is reflected in the fact that although the current exceeds the rated value, the extent of the excess is not large and generally does not form a large inrush current.
1. Causes of inverter overload
a. The mechanical load is too heavy during the operation of the equipment. The main characteristic of overload is that the motor heats up and the current value is displayed on the display.
b. The three-phase voltage is unbalanced, causing the operating current of a certain phase to be too large, resulting in overload tripping. This is characterized by uneven heating of the motor, which may not be found when reading the operating current from the display (because the display only displays one phase current).
c. Malfunction, the current detection part inside the frequency converter fails, and the detected current signal is too large, resulting in tripping.
2. How to check whether the frequency converter is overloaded
a. Check whether the motor is hot. If the temperature rise of the motor is not high, you should first check whether the preset of the electronic thermal protection function of the inverter is reasonable. If the inverter still has margin, the preset of the electronic thermal protection function should be relaxed. value.
If the temperature rise of the motor is too high and the overload occurs is a normal overload, it means that the motor is overloaded. At this time, the first thing to do is to increase the transmission ratio appropriately to reduce the load on the motor shaft. If it can be increased, increase the transmission ratio. If the transmission ratio cannot be increased, the capacity of the motor should be increased.
b. Check whether the three-phase voltage on the motor side is balanced. If the three-phase voltage on the motor side is unbalanced, then check whether the three-phase voltage on the output end of the inverter is balanced. If it is not balanced, the problem is inside the inverter.
If the voltage at the output end of the frequency converter is balanced, the problem is on the line from the frequency converter to the motor. Check whether the screws at all terminals have been tightened. If there are contactors or other electrical appliances between the frequency converter and the motor, also You should check whether the terminals of the relevant electrical appliances are tightened and whether the contacts are in good condition.
If the three-phase voltages on the motor side are balanced, the operating frequency at tripping should be known:
If the operating frequency is low and vector control is not used (or no vector control), first reduce the U/f ratio. If the load can still be driven after the reduction, it means that the original preset U/f ratio is too high and the excitation current If the peak value is too large, the current can be reduced by reducing the U/f ratio; if the load cannot be carried after the reduction, consideration should be given to increasing the capacity of the inverter; if the inverter has a vector control function, vector control should be used.
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