Welder Power Supplies

jclarke4 · Nov 14, 2009

Hi,

In an installation there are 6no. Eurarc 420 welders supplied from dedicated 40Amp single phase RCBO's housed within a dedicated distribution baord. The welders can be operated as either single or three phase via a selector switch. The current arrangement is single phase with ABB 32A plug/socket connections. The rated max load in single phase is 93Amps. The users of the welders only use up to 3.25mm electrodes which the manufacturer tells me that using these types of electrodes would only use max of 35Amps.

The RCBO's are 30mA C type and keep tripping out once welding commences. It will be a big job not to mind expensive to change out to hard wired connections via isolators and MCB's so I was proposing to change the RCBO's to D or even K type as the issue may just be in-rush current but I suspect that there may be a problem with earth leakage.

Anybody any thoughts???

John.

benji · Nov 14, 2009

i would check with manufacturer ,iv'e conected loads of welders but theve all been 2 phase the old terminology was single phase 415v ie (2 phase) .rcd's doubtfull

yours benji

boatnik1 · Nov 14, 2009

Had a similar problem years ago. Changed the welders to run on two phase 380/415v to reduce the current and changed the RCBOs for C-MCBs with SY armoured from plug to welder. Most of these welders are either 220/230v single phase or 380/415v two phase and N&E with the cooling fan running from the single phase regardless which way the connections are. Once wired the selector switch would normally be pegged to allow only the selected voltage and off.. Also required to balance the load as much as possible. i.e. Two welders across R&Y , 2 across Y&B, 2 across R&B.

jclarke4 · Nov 15, 2009

boatnik1 said:
Had a similar problem years ago. Changed the welders to run on two phase 380/415v to reduce the current and changed the RCBOs for C-MCBs with SY armoured from plug to welder. Most of these welders are either 220/230v single phase or 380/415v two phase and N&E with the cooling fan running from the single phase regardless which way the connections are. Once wired the selector switch would normally be pegged to allow only the selected voltage and off.. Also required to balance the load as much as possible. i.e. Two welders across R&Y , 2 across Y&B, 2 across R&B.

This type of welder canbe operated either from 230Volt single phase or 400Volt three phase (see attached welder spec). Te 6 welders have a single phase supply each but are distributed over the three phases at the distribution board i.e. 2 welders per phase.

You say that you changed the RCBO's to MCB's but kept the plug/socket connections. Is it not a requirement in the wiring regs that any portable equipment i.e. plug/socket connections must have RCD protection for people protection???

I am trying to overcome the problem without having to hard wire through isolators at the welders and replacing the RCBO's with MCB's but it looks like this might be the only option??

boatnik1 · Nov 16, 2009

The spec on the link for the welder is single phase 230/400v not 3p. so across two phases is the way to go. As regards the MCBs, it was a very long time ago and the spec may have been different then but Iv'e been in a lot of places recently where this has been the way although my own and some others preference would be for fuses. Either MCBs or fuses. Earth leekage is par for the course where welding is concerned as welding tables etc. are earthed so giving a direct strike to earth each time an arc is struck even though the transformer output is isolated from the input..
You would need to check current Regs (not guides) to see what is permitted. I've been retired for years and am a long way behind with the current sometimes nosensical Regs. If the regs don't permit the plugs then 60a isolators and a decent length of SY is the way I'd go. 60A isolators shouldnt cost a fortune.

ryanryan · Nov 16, 2009

you could try D type mcbs

maddfridge · Nov 16, 2009

jclarke4 said:
Hi,

In an installation there are 6no. Eurarc 420 welders supplied from dedicated 40Amp single phase RCBO's housed within a dedicated distribution baord. The welders can be operated as either single or three phase via a selector switch. The current arrangement is single phase with ABB 32A plug/socket connections. The rated max load in single phase is 93Amps. The users of the welders only use up to 3.25mm electrodes which the manufacturer tells me that using these types of electrodes would only use max of 35Amps.

The RCBO's are 30mA C type and keep tripping out once welding commences. It will be a big job not to mind expensive to change out to hard wired connections via isolators and MCB's so I was proposing to change the RCBO's to D or even K type as the issue may just be in-rush current but I suspect that there may be a problem with earth leakage.

Anybody any thoughts???

John.

hi there

i would changed the rcbos to mcbs type c or d should solve the problem but when welders were first made all the old type protective devices were good old bs 88 fuses motor rated. Thius is possibly away of over coming the problem. For information is served my apprenticeship with oxfords who made the oil cooled and aircooled trojan, bantams etc.in the 70s rivals to SIP

cheers