Welder tripping MCB

[luminaire]

A

welder[/url] is tripping the 15A MCB. The current range is 25A - 300A

.
Obviously, the MCB needs upgrading, but what about cable size as well?
If it is rated at 300A, does that mean 100A per phase and if so how can you work out the MCB and cable size to something that is going to be reasonable?
Sorry about the pics

 

[Spark123]

The 300A is at 50v which works out at about 15kw, or 5kw or 20ish amps per phase @ 240v. Is there any more information on it?
What type MCB do you have? Type B will probably not withstand the inrush current from it, a type C or even a type D might be required (efli requirements also need addressed). It looks ancient btw!! Oil immersed

 

[^neo^]

you'll need a D type breaker for sure!
Those old oxford oil cooled are a nightmare to use on modern electrics.
Also worth taking off the top and checking the wiring as the bakerlite gets soaked in oil and just arcs out. Also make sure there is oil in it!
Damn good welders when they are working though

Thats about mid 1960's that one

 

[^neo^]

with it flat out i would estimate you'll be pulling about 60amp for the initial arc striking, then drop to around 40-50 amps.

 

[luminaire]

The 300A is at 50v which works out at about 15kw, or 5kw or 20ish amps per phase @ 240v. Is there any more information on it?
What type MCB do you have? Type B will probably not withstand the inrush current from it, a type C or even a type D might be required (efli requirements also need addressed). It looks ancient btw!! Oil immersed

Yeah, it is oil immersed, and although I don't know what type of MCB it is at the moment I might well be considering using D type. Also it doesn't appear to be RCD protected!

 

[Spark123]

with it flat out i would estimate you'll be pulling about 60amp for the initial arc striking, then drop to around 40-50 amps.

Is that per phase or total?

 

[Spark123]

The 300A is at 50v which works out at about 15kw, or 5kw or 20ish amps per phase @ 240v. Is there any more information on it?
What type MCB do you have? Type B will probably not withstand the inrush current from it, a type C or even a type D might be required (efli requirements also need addressed). It looks ancient btw!! Oil immersed

Yeah, it is oil immersed, and although I don't know what type of MCB it is at the moment I might well be considering using D type. Also it doesn't appear to be RCD protected!

Does the supply really need to be RCD protected - it is used outdoors? Might be an idea to look at BS88 fuses also, the efli for a 32A type D is very low, looking in GN3 (got my new one today) is 0.29 ohms measured!

 

[^neo^]

Well, im no electrician ( a welder instead) , but we had a very similar spec machine years ago and the sparky who wired up the workshop tested it as drawing 60a on strike up so put a 64a supply and d type breaker.
You'll probably never use it at 300a unless you're welding inch plate with 1/4" rods!

 

[Spark123]

You'd probably need the transformer on your doorstep for a D63A MCB (0.15 ohms max measured)

 

[^neo^]

You'd probably need the transformer on your doorstep for a D63A MCB (0.15 ohms max measured)

I'll check whats on the consumer unit tomorrow and post up what we're running

 

[Fuseblower]

with it flat out i would estimate you'll be pulling about 60amp for the initial arc striking, then drop to around 40-50 amps.

Is that per phase or total?

I've had experience of these welders. They only run from 2 out of the 3 Phases. ie 2 wire 415V supply.(plus earth of course!)
IMHO at 15Kw that would be at least a 63A type D breaker.and 10mm2 cable!
Having said that, It would be very rare to run the welder at absolute max power. For general work the 80V range would probably be in use so allowing for "diversity"(???) a smaller cable and MCB would be in order. The cable and 415V plug in the picture looks like 4mm (max) SY and a 20A CEE type plug.

 

[GaryMo]

Might be an idea to look at BS88 fuses also, the efli for a 32A type D is very low, looking in GN3 (got my new one today) is 0.29 ohms measured!

My thoughts exactly. I've opted for 63A BS88 fuses for a particular job due to not being able to meet the disconnection time for a D63 MCB.

 

[Taylortwocities]

You'd probably need the transformer on your doorstep for a D63A MCB (0.15 ohms max measured)

I'll check whats on the consumer unit tomorrow and post up what we're running

You wont be running that through a consumer unit!
Running a supply for this will need a spark with good test gear and expertise. You have to make checks on the circuit before changing fuses or usung C or D curve MCBs.

 

[ban-all-sheds]

I've got one of those!

Not so big - just the domestic model which doesn't trip a 32A type 1, (but does take out a 13A BS1362 ).

No wheels either, so even though it's smaller, it's a b****r to move around, but at only ( ) 55kg one person can hoist it into a car boot.

Has a very useful 12V high current output for single-ended carbon rod brazing of thin metal.

As ^neo^ said - damn fine bit of kit.

 

[luminaire]

you'll need a D type breaker for sure!
Those old oxford oil cooled are a nightmare to use on modern electrics.
Also worth taking off the top and checking the wiring as the bakerlite gets soaked in oil and just arcs out. Also make sure there is oil in it!
Damn good welders when they are working though

Thats about mid 1960's that one

Do you happen to know what oil to use if it needs topping up?
As you can see it's pretty dirty and oilly everywhere, so the chances are it will need topping up.