Lecky query

[500e]

Friend just bought a Miller Syncrowave running on 2 phase he picks it up when he plugged it in at his workhop it blew the trip (D type).
Checked wiring all OK took it back from whence it came all OK returned home blew trip.
Changed the 2 phase wires round & all OK ??.
Reversing wires blows trip
Any ideas there is no neutral only the 2 phases & earth

 

[Dee J]

I think more information is needed.... 2 phase but no neutral? How is that possible? What voltage? What current? What cable core colours? Confused.

 

[dobbslc]

What supply is he plugging it into?
240v single phase, 3phase???

 

[carbon]

Picture of the data plate may help

 

[500e]

Whats to confuse welder running what is called 2 phase 440 volts across 2 phases no neutral required colors are nice but don't change anything using L1 L2
Single phase, connected across two lines. 17th Ed terminology is a slight improvement in that respect.

 

[rcx132]

You can get three phase that doesn't have neutral. Each phase is just wired across two of the L wires and there are three pairs possible with three wires.

Didn't know two phase existed but I'm no expert.

 

[Dee J]

Ok. So its running on two phase lines off a 3 phase supply. But that doesn't make it 2 phase.... It doesnt have a neutral or a third phase for reference. So in effect it is single phase at whatever voltage its spec'd at. Swapping the two lines should have no effect. So still a puzzle.

 

[Turbo]

There maybe a cooling fan that doesn't like running backwards, reversing the phases would change the direction but I don't see how that would trip the mcb.

 

[rcx132]

Whats to confuse welder running what is called 2 phase 440 volts across 2 phases no neutral required colors are nice but don't change anything using L1 L2
Single phase, connected across two lines. 17th Ed terminology is a slight improvement in that respect.

I thought the 440v is the total of the three phases. Each phase is still only 240v.

 

[rcx132]

There maybe a cooling fan that doesn't like running backwards, reversing the phases would change the direction but I don't see how that would trip the mcb.

This sounds right to me. With two wires only single phase is possible.

 

[Turbo]

I thought the 440v is the total of the three phases. Each phase is still only 240v.

If you measure across 2 phases of a 3 phase 440v supply you should get 440v. Measure between a phase & neutral & you get 240v.

So the welder will be getting 440v across the 2 phases.

 

[rcx132]

If you measure across 2 phases of a 3 phase 440v supply you should get 440v. Measure between a phase & neutral & you get 240v.

So the welder will be getting 440v across the 2 phases.

Ah!

 

[Dee J]

There maybe a cooling fan that doesn't like running backwards, reversing the phases would change the direction but I don't see how that would trip the mcb.

Ac delivered over two wires doesn't work like that. You can reverse a three phase motor by swapping wires... But not a single phase motor - even if it is running off two phase wires of a three phase supply.

 

[andymfell]

what voltage is it set for ?

there is a set of jumpers to select the input voltage

check page 31 in the owners manual
https://www.millerwelds.com/files/owners-manuals/O359H_MIL.pdf

 

[Barking Mat]

I have the same. Runs off 2 phases of 440. I have the same problem, on plug in it wants to trip the main house MCB or RCD just get assistant\ wife to stand by main trip as you keep trying. Really.

 

[500e]

BM the type D MCB allows for the inrush current of bigger welders Motors etc if you have the D type
please reverse the phase wires in the plug would be interested in the result
* PLEASE note picture is of a single phase unit 240volt

Andy he has the manual jumpers correctly set,
I think that people get confused with 2 phase \3 phase the correct name for what is commonly 2 phase should be single phase 440 V or what ever the local voltage is in your country.
If you have 3phase you can get say 440 volts by using any combination of L1 L2 L3 to get 440V, IF you use either L1, L2, L3, + Neutral you can then have 3 separate 240 V supplies.
It can be used in this configuration to balance the incoming if there is a heavy demand for single phase,.
This is usually done in factory or large buildings & the split is floors, departments, so the likelihood of you finding 2 phases next to each other is less.
Then in some rural area they have split phase + neutral. not 3 phase
Have not read the regs for years so likely out of date by 3\4 editions
Had a good look at the machine manual ( going to look at it with him Tuesday ( he was a sparks for 20+ years& is confused as well) but still don't understand the reversal clearing problem, not seen the machine only circuit of Miller's site, don't know if PF is present on this machine but again still don't see how it would effect it in this way
Is there something simple \stupid I am missing

 

[brightspark]

that breaker is only single pole and used on 240v only . if u are using 2 phase 440 v u need a triple pole 3 phase breaker and only use 2 poles

 

[500e]

IT was a picture of a single pole D type if people don't know the difference Darwin will win
Never liked Gerin anyhow

 

[brightspark]

IT was a picture of a single pole D type if people don't know the difference Darwin will win

should have shown a 3 pole one . most people wouldn't have a clue on 3 phase gear or single