Home Lathe with 3 Phase inverter tripping mains

[Wicked]

Hello - hope someone can advise please.

I have a recently purchased second hand Myford lathe which has a 3-phase inverter (Siemens Micromaster 410)

Lathe all works fine but regularly trips my RCCB 80A 30mA breaker taking out half of the board - usually when first powering on. The inverter is plugged into my downstairs ring main which has a Crabtree MCB B32 breaker but it is always the RCCB that trips.

A PAT test of the inverter reveals that Ileak is 7.29mA which I understand is over the limit of 5mA and is therefor a fail.

The manual for the inverter says that if a RCD is used it must be an RCD Type B. The downstairs ring is protected by a Crabtree MCB 32A

Lathe works just fine if I power it from my inverter generator (no Ground of course)...

There is an option on the inverter to remove the Y Capacitor link if it is used on an ungrounded supply - but I guess that will have safety issues.

So anyone have any ideas to stop the inverter tripping the mains (I'm guessing the fact that it is also an inductive load doesn't help)

Thanks

Dave

 

[DPG]

It would be better if it could be fed from a dedicated RCD/RCBO rather than sharing with several other circuits. The combined leakage on your existing RCCB could be on the threshold of its trip point.

I'm no expert on inverters but some of the other members are very knowledgeable and might have some good advice.

 

[Wicked]

Thanks but I can’t do that unfortunately - no easy way to get a new cable from the board to the location of the lathe.

Would changing the MCBO for a switch and changing all the MCBs for RCDs be an option on this half of the board?

 

[James]

I have a customer with lots of small machines that are regularly moved around to suit the work they are doing at the time.
most of the machines that have inverters in them were troublesome when plugged into rcd sockets.
we have slowly worked round the ones that trip rcd’s and installed an isolating transformer in each one.
problems have now gone away.

 

[Wicked]

I have a customer with lots of small machines that are regularly moved around to suit the work they are doing at the time.
most of the machines that have inverters in them were troublesome when plugged into rcd sockets.
we have slowly worked round the ones that trip rcd’s and installed an isolating transformer in each one.
problems have now gone away.

Thanks - is there such a thing as an isolating transformer that can be plugged in to the ring main then the 13A plug on the inverter plugged in to the transformer?

 

[James]

Not as far as I know.
it could be added to the machine control panel though.

 

[DPG]

There are isolating transformers available in plastic or metal cases that offer a built in 13A mains socket to feed your equipment.

 

[James]

Carroll & Meynell 3000VA Intermittent Isolation Transformer 230V/230V Blue - Screwfix

Order online at Screwfix.com. Rugged portable isolating transformer, designed to ensure an isolated supply when working on equipment connected to the mains supply. With a resettable thermal cut-out in the primary circuit to prevent overload. Glass-reinforced polymer case provides IP44 ingress...

www.screwfix.com

 

[DPG]

Carroll & Meynell 3000VA Intermittent Isolation Transformer 230V/230V Blue - Screwfix

Order online at Screwfix.com. Rugged portable isolating transformer, designed to ensure an isolated supply when working on equipment connected to the mains supply. With a resettable thermal cut-out in the primary circuit to prevent overload. Glass-reinforced polymer case provides IP44 ingress...

www.screwfix.com

Exactly what I was thinking of. Many TV repair people used these. That's television, not transvestite. But that's nothing against any transvestite television repair people. Mmm, think I covered that ok.

 

[Wicked]

Thanks both - at the risk of being accused of being premature (hate it when that happens I found that exact device in the Screwfix catalogue and ordered one earlier on today - I'm picking it up tomorrow. Assuming I don't burn the house down or electrocute myself I'll report back tomorrow.

Looking at the instructions on the Inverter it says I must cut the Y Capacitor link if using it on an ungrounded supply. When I run the inverter powered by my Pure Sine Wave petrol generator it works just fine, and I guess that is seen as an ungrounded supply. I'll try it with the new isolating transformer and se what happens first before cutting the link.

Thanks all for your helpful advice. Dave

 

[Wicked]

Just an update - the Isolation Transformer from Screwfix fixed the tripping problem - so thanks to @James and @DPG for the advice.

You have also probably saved my marriage as the risk of tripping the mains during an episode of Classic Coronation Street was just too great!

Thanks

Dave

 

[DPG]

Just an update - the Isolation Transformer from Screwfix fixed the tripping problem - so thanks to @James and @DPG for the advice.

You have also probably saved my marriage as the risk of tripping the mains during an episode of Classic Coronation Street was just too great!

Thanks

Dave

Excellent. To be fair it was James who solved this one.

Got to say I would sooner be in the garage watching the lathe than in the house watching Coronation Street