Delta overload trip fault solution

1. The main cause of VFD overload

(1) Mechanical overload. The main characteristic of overload is the motor heating, which can be found by reading the running current on the display screen.

(2) 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 detected when reading the running current from the display (because the display only shows one phase of the current).

(3) Problem: the internal current detection of VFD is faulty. The detected current signal is too large, leading to tripping.

2.VFD view the overloaded method

(1) Check whether the motor is hot. If the temperature rise of the motor is not high, the first should be

Check whether the preset value of the electronic thermal protection function of the VFD is reasonable. If there is a margin in the VFD, the preset value of the electronic thermal protection function should be relaxed.

If the temperature rise of the motor is too high, the overload is normal, indicating that the motor is overloaded. At this time, the first thing is whether the transmission ratio can be properly increased to reduce the load on the motor shaft. If you can, add the gear ratio. If the transmission ratio cannot be added, the capacity of the motor should be added.

(2) Check whether the three-phase voltage at the motor side is balanced. If the three-phase voltage on the motor side is not balanced, check whether the three-phase voltage at the output of the VFD is balanced again. If it is also unbalanced, the problem lies within the VFD.

If the voltage at the output of the VFD is balanced, the problem lies in the line from the VFD to the motor. Check that all terminal screws are tightened. If there are contactors or other electrical appliances between the VFD and the motor, check whether the wiring terminals of relevant electrical appliances are tightened and whether the contact is good.

If the three-phase voltage on the motor side is balanced, the operating frequency should be understood when tripping:

If the operation frequency is low and vector control is not used (or not used), the U/f ratio is lowered first. If the load can still be driven after falling, the original preset U/f ratio is too high, and the peak value of the excitation current is too large. The current can be lowered by decreasing the U/f ratio. If there is no static load after reduction, the capacity of VFD should be added; If the VFD has vector control function, vector control should be used.