Handling of overload trip fault of inverter of blow molding machine

Handling of overload trip fault of inverter of blow molding machine

The overload trip of the converter is one of the common problems in the operation of blow molding machine.

The overload trip of frequency converter should be dealt with by scientific and effective method.

This article will introduce the reasons and solutions of inverter overload trip in detail.
What is blow molding machine inverter overload?
The motor may turn, but the running current exceeds the rated value, which is called overload. The basic reflection of overload is that the current exceeds the rated value, but does not exceed the rated value by a large margin, and generally does not form a large impulse current.

What is the cause of overload trip of blow-molding machine converter?
There are three main reasons

1. Wrong behavior

The current detection part of the converter is faulty, and the detected current signal is too large, resulting in tripping.

2. Large mechanical load

The main characteristic of overload is the heating of the motor, which can be detected by reading the running current from the display.

3. The unbalance of three-phase voltage leads to excessive running current of a phase, resulting in overload tripping.

It is characterized by uneven heating of the motor, which may not be found when reading the running current from the display (because the display only shows one phase of the current).

To find the reason, we should think about the converter overload treatment method.

How to deal with overload trip of blowing machine converter?

1. Check whether the three-phase voltage at the motor side is balanced

If the three-phase voltage on the motor side is not balanced, the three-phase voltage on the output side of the inverter should be checked again. If it is not balanced, the problem is in the inverter. The inverter module and drive circuit of the converter should be checked.

If the voltage output of the converter is balanced and the problem is in the circuit between the converter and the motor, check that all bolts at the terminal are tightened.

If there are contactors or other electrical appliances between the frequency converter and the motor, check whether the wiring terminals of relevant electrical appliances are tightened and whether the contacts are in good contact state.

If the three-phase voltage on the motor side is balanced, the operating frequency during tripping should be known.

If the working frequency is low and there is no vector control (or no vector control), the U/F ratio should be reduced first. If the load can still be driven after the reduction, it indicates that the preset U/F ratio is too high and the peak value of the excitation current is too large, and the current can be reduced by reducing the U/F ratio.

If the reduction is carried out with a fixed load, consideration should be given to increasing the capacity of the inverter, and if the inverter has a vector control function, the vector control mode should be used.

2. Check whether the motor is hot

If the temperature rise of the motor is not high, it is necessary to check whether the preset value of the electronic thermal protection function of the frequency converter is reasonable. If the frequency converter has room, the preset value of the electronic thermal protection function should be relaxed. There is no need to relax. According to the required production process, the overload phenomenon is normal overload, which indicates that the frequency converter is improperly selected. The capacity of the frequency converter should be increased and the frequency converter should be replaced.

When the motor is driving variable load or intermittent load, as long as the temperature rise does not exceed the rated value, overload is allowed for a short time (a few minutes or tens of minutes), but the frequency converter is not. If the temperature rise of the motor is too high, and the overload is normal overload, it indicates that the load of the motor is too heavy. At this point, the transmission ratio should first be properly increased to reduce the load on the motor shaft. If possible, the transmission ratio should be increased. If the transmission ratio cannot be improved, the capacity of the motor should be increased.

3. Check for misoperations

If all the above checks are OK, you should check for error. The method of inspection is to measure the output current of the converter with an ammeter under light load or no load, and compare it with the running current value displayed on the display screen. If the current reading displayed on the display screen is much larger than the actual current, it indicates that the error of the current measurement part inside the converter is large, and the "overload" trip may be wrong action.

The reason for the overload trip of the blowing molding machine frequency converter and the treatment method is said here. When the overload trip of the blowing molding machine frequency converter occurs, the above steps will be followed to solve the problem quickly and effectively.