Dealing with >30 mA Residual Current due to an industrial servo drive in a 'man cave' scenario on residential electrics? UK Based Location.

Hi All,

Long story short, I have a man cave that runs off my home's main board. The main board was recently upgraded and is 18th reg compliant. My workshop is fed with a 32A RCBO which then goes into a sub DB which has a Wylex Isolator and then feeds into another 32A RCBO.

I can run most of my machines without issue and I create 3 phase using VFDs. One specific Servo Drive however needs 3 phase and is fed from a VFD which then in turn powers the Servo Drive (so VFD into VFD). This trips my RCBO.

The manual suggests that the Servo Drive (7.5KW/ 10 HP) should sit behind a 200mA RCD, otherwise its likely to trip. This is their exact wording.

"Cause: the leakage protection switch trips after the servo spindle start-up. Reasons and countermeasures: 1.A plain leakage protection switch with a leakage protection value of 200mAis recommended; otherwise candle the leakage protection switch; 2.Use the specified leakage protection switch dedicated to servo(or transducer) with a leakage protection value of 30mA; 3.Add an isolating transformer between the plain leakage protection switch and servo driver."

What are my options in the UK to deal with this?

Thanks in advance.

  • If you are running a 7.5 kW device, that is the whole of your 32 A supply, so do you run it in the dark?

    You may be limited by a TT supply, but does the same apply to the (potential) purchaser?

    Rather than a VFD, might a mechanical SP to TP converter be an option?

  • Yep, I run it by candle light :-) ... no, I make do. I take light cuts, watching the current I only take 4-5 Amps. My Screw Compressor runs at the same time and that takes 9 Amps at Full Load. When you talk Mechanical, you mean a Transwave or similar? Yep, its an option. I am waiting to speak to the potential buyer's electrician to understand what he has. I'm aware he has a much larger Single Phase supply (70 or 100Amps, dont remember the figure) but it was plenty more than mine.