One for you sparkies!
Discussion
Right, here's the story. I've been offered an industrial welder (cheap, of course :D ). It's a single-phase unit, but has a red industrial plug on it.
From the maker's website I find that their 1ph units have two 'Live' terminals and an Earth for the mains input.
Am I right in thinking that this unit needs two of the three phases from a 3ph supply and Earth (no Neutral), or could I get lucky and run it from the domestic L,N &E (obviously at reduced output current so as not to pop the house fuse)?
If not why not, 'cos my grasp of 3ph has always been a bit dim... :D
From the maker's website I find that their 1ph units have two 'Live' terminals and an Earth for the mains input.
Am I right in thinking that this unit needs two of the three phases from a 3ph supply and Earth (no Neutral), or could I get lucky and run it from the domestic L,N &E (obviously at reduced output current so as not to pop the house fuse)?
If not why not, 'cos my grasp of 3ph has always been a bit dim... :D
Wedg1e, Sounds like it's a 415v plug you have there, so it's likely to be using 2 phases of a 3ph supply (415v). How large is the plug? How many pins? Any current markings on the plug? 16A 0r 32A maybe?
If it's designed for a 415v input voltage then it's unlikely to work on a 240v supply. For the same "work" at approx Half the voltage you would need to draw twice the current (keeping it simple).
No difference in frequency though, still 50Hz (or c/sec in old money)
Is it a large heavy industrial welder on wheels?
>> Edited by 8Pack on Sunday 12th June 03:24
If it's designed for a 415v input voltage then it's unlikely to work on a 240v supply. For the same "work" at approx Half the voltage you would need to draw twice the current (keeping it simple).
No difference in frequency though, still 50Hz (or c/sec in old money)
Is it a large heavy industrial welder on wheels?
>> Edited by 8Pack on Sunday 12th June 03:24
Wedg1e, A quick lesson in power generation. 
The diagram above shows you the "Star connected" arrangement of the coils in a power station generator. Mounted at 120 degrees apart so that one revolution of 360 degrees will generate a 3 phase (3 sine wave) supply.
The voltage is generated at a higher level but is tranformed down for industrial use and the voltage between the points: L1-L2-L3 is 415v.
Voltage between the centre "star point" and either L1 or L2 or L3 is only 240 volts (for domestic use) and in any street the houses are divided up between the 3 phases to equalise the load.
The "star point" is what we use in our homes for "Neutral and Earth"
The voltage of one phase (i.e. 240v) multiplied by Root3 (1.732) is:.....415v. The voltage between each phase.......L1-L2-L3.
Hope that helps! Large Industrial welders ARE usually 415v, check for labels!
>> Edited by 8Pack on Sunday 12th June 04:21
The diagram above shows you the "Star connected" arrangement of the coils in a power station generator. Mounted at 120 degrees apart so that one revolution of 360 degrees will generate a 3 phase (3 sine wave) supply.
The voltage is generated at a higher level but is tranformed down for industrial use and the voltage between the points: L1-L2-L3 is 415v.
Voltage between the centre "star point" and either L1 or L2 or L3 is only 240 volts (for domestic use) and in any street the houses are divided up between the 3 phases to equalise the load.
The "star point" is what we use in our homes for "Neutral and Earth"
The voltage of one phase (i.e. 240v) multiplied by Root3 (1.732) is:.....415v. The voltage between each phase.......L1-L2-L3.
Hope that helps!
Large Industrial welders ARE usually 415v, check for labels! >> Edited by 8Pack on Sunday 12th June 04:21
pearl nicholas said:
it prob has a voltage selection link somewhere, maybe in the terminal box so that it can be used on a 240v supply although it may be far too heavy on the juice for domestic use
I tend to agree, anything other than a little "toy" welder for very thin metals is likely to be too heavy for a domestic supply. Just how big is this thing Wedg1e?
It's rated at 77A from 220V (and 48A at 415v) when running flat-out at 300A secondary. I wasn't planning on using more than about half that 
IIRC the main fuse for the house is 100A; my aircon draws 60A on startup but that's nowt compared to what the welder will do to it
Look, I said it was cheap. Have you seen the cost of AC/DC TIG welders!?
IIRC the main fuse for the house is 100A; my aircon draws 60A on startup but that's nowt compared to what the welder will do to it
Look, I said it was cheap. Have you seen the cost of AC/DC TIG welders!?
wedg1e said:
Right, to clarify: the welder is multi-voltage (IIRC 220/380/415) and is clearly labelled 'Single Phase 50 Hz'.
So I was wondering if single phase across say red and blue of a 3ph supply at 220v is the same as that at 220v L to N on a domestic....
No it's not.
The whole situation depends very much on what you've got and are trying to do.
With motors, you can't use a 3ph motor on a 1ph supply, unless you have an inverter, but you can use a 1ph motor on a 3ph supply.
I'm wondering if your welder is wired up from one of the three phases to neutral?
Overall it might work, because welders can be more flexable. If it's within the capacity of the unit to operate from a 1ph supply you can use it at home. It's just that it won't be as capable as if you were to use it from a 3ph supply.
In the end, if you crank the amps up on the welder, the breaker will just pop out.
The other thing to bear in mind is that you really want to try and keep it's supply separate from things like computers, TV's and VCR's.
I don't think that the japs really protect their home entertainment kit such that it can work alonside big nasty inductive loads.
>> Edited by dilbert on Sunday 12th June 17:27
Just check out the new regulations!
Don't you just love that black to blue connection!
www.amicustheunion.org/PDF/FixedWiringChange.pdf
Don't you just love that black to blue connection!
www.amicustheunion.org/PDF/FixedWiringChange.pdf
Your neighbours who are on the same phase as you are gonna love resetting their clocks when you fire that up ! 
Gassing Station | The Pie & Piston Archive | Top of Page | What's New | My Stuff