When a motor can rotate normally, but the operating current exceeds the rated value, it can be called overload. The basic reflection of overload is that although the current exceeds the rated value, it does not exceed much, and generally does not form a large inrush current. But have you learned about the overload of the frequency converter (Variable-frequency Drive, VFD)? The following content will give you a brief introduction.

1. The main reason for VFD overload

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

(2) The unbalanced three-phase voltage causes the operating current of a certain phase to be too large, resulting in overload tripping. It 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 shows one-phase current).

(3) Fault, the internal current detection part of the VFD is faulty, and the detected current signal is too large, resulting in tripping.

deal overload trip of vfd

2. The method of VFD checking overload

(1) Check whether the motor is hot. If the temperature rise of the motor is not high, the first step 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 and the overload is normal, it means that the motor is overloaded. At this time, first of all, whether the transmission ratio can be appropriately increased 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.

(2) Check whether the three-phase voltage on the motor side is balanced. If the three-phase voltage on the motor side is unbalanced, check whether the three-phase voltage at the VFD output is balanced again. If it is also unbalanced, the problem is inside the VFD.

If the voltage at the output of the VFD is balanced, the problem is in the wiring from the VFD to the motor. Check that all terminal screws are tight. If there is a contactor or other electrical appliances between the VFD and the motor, check whether the terminals of the 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 known when tripping:

If the operating frequency is low and vector control is not used (or vector control is not used), 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 peak value of the excitation current is too large. The current can be reduced by reducing the U/f ratio. If there is no static load after reduction, the capacity of VFD should be increased; if VFD has vector control function, vector control should be adopted.

When a motor can rotate normally, but the operating current exceeds the rated value, it can be called overload. The basic reflection of overload is that although the current exceeds the rated value, it does not exceed much, and generally does not form a large inrush current. But have you learned about the overload of the frequency converter (Variable-frequency Drive, VFD)? The following content will give you a brief introduction.

1. The main reason for VFD overload

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

(2) The unbalanced three-phase voltage causes the operating current of a certain phase to be too large, resulting in overload tripping. It 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 shows one-phase current).

(3) Fault, the internal current detection part of the VFD is faulty, and the detected current signal is too large, resulting in tripping.

deal overload trip of vfd

2. The method of VFD checking overload

(1) Check whether the motor is hot. If the temperature rise of the motor is not high, the first step 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 and the overload is normal, it means that the motor is overloaded. At this time, first of all, whether the transmission ratio can be appropriately increased 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.

(2) Check whether the three-phase voltage on the motor side is balanced. If the three-phase voltage on the motor side is unbalanced, check whether the three-phase voltage at the VFD output is balanced again. If it is also unbalanced, the problem is inside the VFD.

If the voltage at the output of the VFD is balanced, the problem is in the wiring from the VFD to the motor. Check that all terminal screws are tight. If there is a contactor or other electrical appliances between the VFD and the motor, check whether the terminals of the 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 known when tripping:

If the operating frequency is low and vector control is not used (or vector control is not used), 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 peak value of the excitation current is too large. The current can be reduced by reducing the U/f ratio. If there is no static load after reduction, the capacity of VFD should be increased; if VFD has vector control function, vector control should be adopted.

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