Have you tried testing the RCD on ramp and without the device connected

It’s been sent back to China for tests. Despite what you all might be thinking, this is a reputable brand.

If you cannot test it when disconnected i’d guess it’s beyond use.

Yep. Needs replacing. It has been suggested to bypass the RCD. I’m not ready to do this. I believe there’s a problem rather than nuisance tripping 

How old is the circuit and why has it now started operating under no load?

Two weeks old. Was tested and inspected and commissioned by the manufacturer 

At a guess, you have a NE fault or your device is at fault. Really hard to say without looking at the circuit 

I installed the final circuit. C50 mcb,100 Amp 300mA type B RCD to the machine isolator. To cause a 300mA RCD to trip o would expect 200mA as a minimum to be leaking out somewhere.!

No NE fault on the supply but possibly on the machine. . >999 on all IR tests up-to the isolator 

300mA type B. Does the type B pick up frequency as well as DC leackage? Have you got an inverter connected that is faulty? Type B’s do DC and frequency. 

Yep, 3 inverters. Motor overloads st at 8 Amps

Yep, 3 inverters. Motor overloads st at 8 Amps

Good question. The speed has been played around with (Frequency) 

You can adjust the speeds at the HMI

Its very hard to say without looking at it. If it fails under no load and the neutral is disconnected I’d go for the device. But if neutral is connected and it has loads attached i’d look at the load. I am not an expert RCDs have always been neutral issues in my previous experience 

If you do find the fault I interested

It’s a machine fault that is blowing RCDs. I replaced the RCD and it ran for 4 days and now will not reset load free. I believe there a earth leakage fault >200mA. I have not considered frequency as being a problem. Having spoken with the operator that had increased the speed.

The only time I seen this happen was a three phase RCD that was three pole with single phase loads on it. Got it replaced with a four pole RCD and was okay

These are 4 pole RCDs

3 phase. No neutral 

Neutral installed to the machine but not utilised 

Theres a good document out there that shows how type b rcds are good for picking up high frequency hamonics for mode four ev chargers. They can burn out type a rcds