RCD protection for portable equipment with Inverters

[gerard]

Case closed then! Thanks for that.

 

[Inteificio]

Hi possibly a stupid point, but not dealt with inverters before.

If you want an RCD can you not insert one after the inverter? eg an RCD socket.

The current leakage in the inverter might not affect the circuit after...or it might, for some reason can't get my head around it this early in the morning.

 

[clicon357]

Case closed then! Thanks for that.

Whoa there! Lets open the box on this one again. I think I can help:

Go back 10 years and my company were importing kit from abroad fitted with S** (major German company) motors and inverters. The kit we were importing itself had no rcd protection but when we plugged it into the supplies provided on site then we would get tripping problems about 25% of the time (not 25% of the sites but like 1 in 4 times on the same site), this was always where there was 30mA protection. I did some digging and investigated options. Seems that inverters are naturally leaky to earth because of EMF circuitry and that on occasion the leakage was enough to trip the RCD. I contacted the drive/motor maker who's suggestions were 1) fit a drive WITHOUT EMF filters and / or 2) protect with a 100mA RCD. The first, ditching the filtration was unacceptable as it gave us issues with CE marking of the kit. The 100mA RCDs were unaccepable to the sites we were working on. This went on with no real resolution. One S** drive was changed to I think a Jag*** drive that had no fitration and that worked - the CE issue was ignored. Another site was changed to 100mA with non standard 3-phase connections (7-pin) until the client's insurer kicked off. It was because of that site I had to sort it once and for all. I came across the Merlin Gerin range of "Si" units which are specific for sensitive installations. They are NOT as such a time delay type. Had a bit of a time getting them as nobody had heaard of them. Ended up getting two 40A Si units from France via my Telemechanique supplier. Bottom line it worked. Details here:

http://www.engineering.schneider-el...n_against_nuisance_tripping_voltage_surge.pdf

As an interesting follow up to this I then got a letter from S** (they're a huge manufacturer and by comparison I'm Joe Nobody) some time later asking IF I HAD MANAGED TO FIX THE PROBLEM! Understandably I was a bit peeved so called them up. It turned out that they had supplied a customer with something like 200 drives that had gone into kid's fairground style rides - I think the small ride on sort that you stick 50p in and you see at shopping centres. Guess what, a fair proportion were tripping. I suggested the Si RDs from Merlin. I have an excellent relationship with S** seemingly on the back of this in part and use them to this day as my preferred motor/drive supplier.

Hope this helps.

 

[netblindpaul]

clicon,
I know the company Jag***.
I am struggling with the S**?
I know of a large German drives manufacturer, but not just a 3 letter name.
I can think of one possibility, but I did not think they were German, any chance of letting me know to satisfy my curiosity please?
PM if you don't wish the name to be in open forum?
I actually worked for a German drives company at one time, not the one you are describing I think.

 

[Darkwood]

Thanks for link Clicon..... got Sneider catalogues but old ones and dosnt show SI or type B units been looking for a device like this for ages. .......... much appreciated.

 

[srewolf21]

Not sure if I'm barking up the wrong tree but the way I understand how inverters work there is a good chance they may introduce harmonics on to the system which will change the characteristics of the supply frequency and in certain circumstances will increase the neutral current in relations to a RCD obviously a increased neutral current would result in the device tripping.
It may be because harmonics are new to me and I'm seeing potential problems everywhere but with inverters I think this could be a real possibility.

 

[Knobhead]

Gerard, if you are so worried about earthing of portable equipment then maybe you should look at earth proving outlets.

 

[clicon357]

clicon,
I know the company Jag***.
I am struggling with the S**?
I know of a large German drives manufacturer, but not just a 3 letter name.
I can think of one possibility, but I did not think they were German, any chance of letting me know to satisfy my curiosity please?
PM if you don't wish the name to be in open forum?

I actually worked for a German drives company at one time, not the one you are describing I think.

You have a PM sent.

 

[Darkwood]

Not sure if I'm barking up the wrong tree but the way I understand how inverters work there is a good chance they may introduce harmonics on to the system which will change the characteristics of the supply frequency and in certain circumstances will increase the neutral current in relations to a RCD obviously a increased neutral current would result in the device tripping.
It may be because harmonics are new to me and I'm seeing potential problems everywhere but with inverters I think this could be a real possibility.

Check out the link on post#18 it will explain why and what causes nuisense tripping etc, it has a section on VSD's too explaining the nature of their leakage and how these effect standard RCD's causing them to trip or even blind them, its a little too involved to explain on here but has diagrams and graphs etc to aid understanding.

 

[clicon357]

Thanks for link Clicon..... got Sneider catalogues but old ones and dosnt show SI or type B units been looking for a device like this for ages. .......... much appreciated.

No problems. Saved us a lot of headache. A mate worked for the then competition and they were using the same drives and having the same problems we were. Over a beer one night it came up and I mentioned our fix. Turns out they had changed their make of drive totally (to Toshiba I think). It was a bit of a pain as their engineers had to learn new bit of sofware for doing the motor start ups etc. Also they kept with the original motor make which meant entering a lot of parameters manually rather than just telling the drive what motor it was running from an pre-loaded list. Think we got our Si RCDs for about £50 a time. If I think of it I'll dig out the invoice and PM you the exact type we used.

 

[Darkwood]

No problems. Saved us a lot of headache. A mate worked for the then competition and they were using the same drives and having the same problems we were. Over a beer one night it came up and I mentioned our fix. Turns out they had changed their make of drive totally (to Toshiba I think). It was a bit of a pain as their engineers had to learn new bit of sofware for doing the motor start ups etc. Also they kept with the original motor make which meant entering a lot of parameters manually rather than just telling the drive what motor it was running from an pre-loaded list. Think we got our Si RCDs for about £50 a time. If I think of it I'll dig out the invoice and PM you the exact type we used.

Appreciate it as ive built some portable drive kits to a company so they can do onsite repairs to machinery, they are 1ph to 3ph but we are clashing with their customers who either have rcd's tripping with our drives or asking us to fit rcd protection to units to allow to be used on site, at presence i just built in extra safety via monitored earth trip and earthed braided cable to reduce risk of shock. Funny thing is im always chatting to tech' at Sneider but never thought to ask as was unaware a device existed. Cheers

 

[gerard]

Gerard, if you are so worried about earthing of portable equipment then maybe you should look at earth proving outlets.

I have thought about this and I will probably give it more consideration

 

[gerard]

Clicon357 - can you PM the manufacturer to me also please?

 

[silva.foxx]

SEW are German and it stands for "Süddeutsche Elektromotoren Werke"

SSB are the other Krautfit I can think of.

What's with all the Secret Squirrel ****e and Masonic PM whispers anyway... they're major manufacturers within our game, just like the mentioned Scheider, Merlin Gerin and IMO Jaguar.

Is there a product placement gagging order in place?

 

[clicon357]

SEW are German and it stands for "Süddeutsche Elektromotoren Werke"

SSB are the other Krautfit I can think of.

What's with all the Secret Squirrel ****e and Masonic PM whispers anyway... they're major manufacturers within our game, just like the mentioned Scheider, Merlin Gerin and IMO Jaguar.

Is there a product placement gagging order in place?

Fair comments. My fault that I just didn't want anyone to be seen in a negative light. Anyway, it was then SEW. Hasn't stopped me using them for about 11 years now and nothing but good service from them on all fronts.

p.s. Love your tag line!