Never use leakage protector when using frequency converter. This is a major principle of the use of frequency converters.

Some customers in the use of the inverter, for the inverter selected the corresponding leakage protector. The final result is: the transducer moves together, the leakage protector moves, the system simply cannot run.

Why?

The principle of leakage protector is that zero sequence current is zero. When using frequency converter, zero sequence current cannot be zero.

The output side of the inverter is PWM wave, and there is the capacitive effect of the long cable between the motor cable and the earth. When the cable with shielding layer is used, the capacitive effect is more obvious. When the inverter is working, the capacitor is charging and discharging. A current flows into the earth through the capacitor and flows back to the inverter from the grounding wire on the side of the input line to form a current loop. If a leakage protector is used on the incoming side, it will act and shut down the system.

SO, don't match leakage protector for your inverter. If you want to ensure safety, do a good grounding of the equipment on the line.

Case study:

Q: an 18.5kw boiler induced draft fan is installed with an 18.5kw inverter. Once the inverter is installed and started, the distribution room will switch off.

The original distribution room was equipped with leakage protector (200mA action, 30mA pulse) on every circuit.

The request for the customer to remove the leakage protection was rejected, and then the carrier frequency was adjusted to 1KHz, and the change in the starting mode of the converter was still not solved.

Finally, it is suspected that the power cord of the motor has leakage, because its length is about 20 meters and it is buried underground, but it is difficult to ask the customer to replace it (the original power frequency is normal).

Is there any simple and effective solution?

Answer: because leakage protector generally detects that the three-phase unbalance degree is more than %20, it will jump to protect. When the inverter is installed, the three-phase unbalance degree will generally exceed %50.

So the leakage protector is bound to jump.

Here are a few ways:

Method 1: leakage protector on the general meeting has a regulator, the regulator can be adjusted;

Method 2: replace the leakage protector with a special leakage protector for frequency converter. There are special leakage protectors for frequency converter on the market.

Method 3: increase the load of the device, that is, the motor load, so that the current leakage of the converter will not be very large when it is started.

Method 4: the leakage protector short.