Why can't Delta inverters be equipped with leakage protectors?
When using Delta Inverter, you must never use a leakage protector. This is a big principle used by Delta inverters.
Some users choose the corresponding leakage protector for Delta inverter when using Delta inverter. The result is that the frequency converter moves together and the leakage protector operates and the system cannot operate at all. Why? The principle of the leakage protector is that the zero sequence current is zero. When using a frequency converter, the zero sequence current cannot be zero.
The output side of the inverter is a PWM wave. There is a capacitance effect between the motor cable and the ground. When using a cable with a shield, the capacitance effect is more obvious. When the inverter is working, the capacitor is charged and discharged, and a current flows through the capacitor into the earth, and flows back from the ground line on the incoming line to the inverter 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 equip your inverter with a leakage protector. If you want to be safe, do a good job of grounding the equipment. Case:
Q: A 18.5KW boiler induced draft fan is installed with a 18.5KW inverter. After the inverter is installed, the power distribution room will jump and the original power distribution room will be switched. A leakage protector (200mA action, 30mA pulse) is installed. Require the customer to remove the leakage protection is rejected, then adjust the carrier frequency to 1KHz, change the inverter startup mode still can not be resolved, it is suspected that the motor power line has leakage, because its length is about 20 meters and buried in the ground, but requires customers to replace There are also difficulties (its original power frequency is normal). Is there any simple and effective solution? A: Because the leakage protector generally detects that the three-phase unbalance is above 20%, it will jump protection. When the inverter is installed, the three-phase unbalance will generally exceed %50, so the leakage protector will definitely jump.