Repair of EDS1000 ENC VFDV Misleading Current Fault

A ENC EDS1000 11kW Inverter will trip to constant speed overcurrent when accelerating to above 40Hz during operation. But in reality, the operating current is much lower than the rated current, and after switching to other frequency converters, the motor runs normally. Check that the six inverter pulse outputs of the driving circuit are all normal. It is determined that the current transformer circuit detection is abnormal. Check the current detection circuit. The output signal of the current transformer is divided by a 3-ohm resistor and a 30 ohm resistor before being supplied to the motherboard. Suspecting that the current transformer is a non-standard product, an external voltage divider network was connected for adjustment. The partial voltage value may not be accurate enough, causing the current sampling value to be too large and mistakenly skipping the current fault. Or there may be drift in the output value of the internal circuit of the current transformer, which can also cause a false skip current fault.

The simplest method is to adjust the external voltage divider network of the current transformer. Reduce the voltage divider resistance value below it to meet the requirements of the subsequent circuit input voltage range. If conditions permit, the panel current display value can be monitored during operation, and the voltage divider resistance value can be adjusted to match the operating current value with the displayed current value. Often in the maintenance department, it is not possible to connect the frequency converter to the rated load for operation. Therefore, first replace the lower resistor with a 100 Ω potentiometer, and then adjust it to the appropriate position during on-site installation and operation.