In the process of using frequency converter, tripping occurs. Overload is one of the main causes of tripping.
Overload can be subdivided into frequency converter overload and motor overload. Usually we see overload phenomenon, it is necessary to distinguish whether the inverter overload or motor overload, for different circumstances to formulate corresponding measures.
The main cause of overload
(1) the main feature of mechanical overload is that the motor is heated and can be read from the display to read the running current.
(2) the three-phase voltage unbalance caused by a phase running current is too large, resulting in the overload trip, which is characterized by motor heating is not balanced, the read operation current from the display can not find (for display show only one phase current).
(3) the malfunction of the current detecting part in the frequency converter of misoperation is too large, and the detected current signal is too large, resulting in tripping.
Method for troubleshooting overload
(1) check whether the motor is hot or not
If the motor temperature rise is not high, it should first check the electronic thermal protection function preset converter is reasonable, such as inverter still margin, you should relax the preset value; if inverter allowed current has no margin, can not relax, and according to the production process, which is part of the normal overload overload is. That the choice of the inverter is improper, should increase the capacity of the inverter, the inverter replacement. This is because the motor is allowed to overload for short periods (minutes or tens of minutes) while dragging the variable load or intermittent load as long as the temperature is not exceeding the rated value, while the frequency converter is not allowed. If the temperature rise of the motor is too high, and the overload appears to be normal overload, the overload of the motor is indicated. At this point, first of all should consider whether to increase the transmission ratio properly, in order to reduce the load on the motor shaft. If you can increase, then increase the transmission ratio; if the transmission ratio can not be increased, you should increase the capacity of the motor.
(2) check whether the three-phase voltage on the motor side is balanced
If the motor side of the three-phase voltage unbalance, should check whether the three-phase inverter output voltage balance, such as the uneven problem in inverter, inverter module should check the inverter and its drive circuit.
As for the voltage balance at the output of the inverter, the problem should be checked whether the screws at all terminals have been tightened on the line between the inverter and the motor. If there is a contactor or other electrical appliance between the inverter and the motor, it should also check whether the terminals of the electrical appliance have been tightened, and whether the contact condition is good or not.
If the motor three-phase voltage balance, should understand the working frequency of the trip: if the working frequency is relatively low, and did not use the vector control (or vector control), the first U/F lower than; such as reducing can still drive the load, then the original preset U/F ratio is too high, the peak flow excitation is too large that can reduce the ratio of U/F to reduce the current; if reduced with fixed load, should consider to increase the capacity of the inverter; if the converter has the function of vector control, vector control mode is adopted.
(3) check for incorrect action
In the above inspection has not found the cause, should check whether it is wrong action. The method is in light load or no-load condition, output current of inverter current meter, compared with the operating current display value, if the current reading display than the current actual measurement is much higher, the inverter internal current measurement part of the error is large, overload trip there may be a false action.