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A customer's leakage circuit breaker will immediately trip when ATV28's earthing terminal is well-grounded. How to stop its leakage circuit breaker no...

Goals and Symptoms

A customer's leakage circuit breaker will immediately trip when ATV28's earthing terminal is well-grounded. How to stop its leakage circuit breaker not to trip if ATV28 is installed and well-grounded ? Does ATV28's internal protection have the same function as leakage circuit breaker has? Can any ATV28's fault code subsitiute the function of leakage circuit breaker?

Causes and Fixes

About SCF:

This fault is detected by the ZCT (zero current transformer).
Trip level is a differential current > 2.5 A

But if there is a 2.5A leakage current (or unbalance between phase)

So we advise to check the earth and unbalanced current with an oscilloscope at the moment of the fault.
If the cable is shielded check that it is correctly connect (no high current circulation in the shield).
Test with disconnecting one side of the shield.
Test with a motor inductance (may be the capacitance of cable and motor is high and generate leak current peak.
Check that the supply voltage is stable and at the good value when the fault occurs.

For the leakage current:

1 - Drive generate a HF leakage current which perturbs the magnetic circuit of the breakers (saturation).
The solutions are
- to use immunized breaker as DPN SI range or RH328AF from MerlinGerin (data in attachment).
- to use motor inductance (long cable only)
- to use eventually RFI filters
- to reduce the switching frequency

2- The other reason is the level of the 50Hz leakage current due principally to RFI filters (internal and external), the cable and motor capacitance, and at power on, to the transient unbalancing between phases.
In this case it's often not possible to reduce this level (you can disconnect the filters but you increase the HF leakage), the only solution we know is to increase the tripping threshold of the breaker.
Generally drives (also our competitors) are not compatible with 30mA differential breakers, we rather advise a 300mA minimum to not trip on power on or to disable the protection during power on.

The values of leakage current depend to the range, you can find a sheet in the GHD Lotus Notes base.

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