Star or Delta?

[normspanners]

An electricians view on this please, Voltages are approximations BTW ie not taking rms into the equation.
I am having, shall we say a 'discussion' at the moment with an electrician regarding a true three phase welder
He says if it is 240 /415 it doesnt matter if it is wired star or delta because it is 240 or 415.
I say in this country you would never wire it up 240 because AFAIK the 240 is for the US market etc because their phases are 110 ish and therefore it actually is 110-110-110 /120 deg angle .220 across any two.
In this country it is 240-240-240 /120deg 415 across any two.
Correct me if I am wrong, I say you could damage the welder by linking it 240 3ph because it is not designed to do this.
He says it is only similar to a 240/ 415 machine where you use one or two phases
I say that a 415 'two' phase wired machine is still actually single phase because it only uses one sinusoidal wave through its transformer and that, one of phase wire actually becomes the neutral return, depending where in the cycle you are.
He says that both the phases 'give' IE two sinusoidal waves, I say that would never work because you need a neutral from somewhere.
Views on this?
Norm

 

[Spark plug]

Your getting confused your electrician sounds to be correct, on a 415v system each one phase + neutral will supply 240v as you said but any 2 phases will supply 415v witch can be used to supply a transformer for example.

I'm not sure what you ment by star and delta with regards a welder after all a welder in its simplest form just a transformer.

Star and delta are different connection methods for motors and generators.

 

[normspanners]

I'm not sure what you ment by star and delta with regards a welder after all a welder in its simplest form just a transformer.

Thanks for your reply,
But I am sorry IMHO you are wrong (but I am not an electrician BTW) a true three phase welder has three transformers, using the three sinusoidal waves, ok it is united as one lump, so therefore it not a simple transformer. It also can be connect 'star' or 'delta' and the waves travel through it in a 'figure 8' fashion and its output is united by the rectifiers as one smoother dc voltage. At 150 hz I think.
A single phase welder is a simple transformer whether it be 240 or 415v because it only uses one wave, at 50 hz

 

[normspanners]

I say you could damage the welder by wiring it 240 3ph because it is not designed to do this.

surely if re linked to 240v and connected to 415v 3ph you are putting twice the designed voltage across the coils !!

 

[AndyStobbs]

I'm not an electrician either - but i don't need to be to see that my welder has 5 options for different input voltages. It must matter or they wouldn't bother.

That kemmpi Dr Nick was selling recently even comes with different units inside depending on the market.

 

[Spark plug]

I'm not an electrician either - but i don't need to be to see that my welder has 5 options for different input voltages. It must matter or they wouldn't bother.

That kemmpi Dr Nick was selling recently even comes with different units inside depending on the market.

Thanks for your reply,
But I am sorry IMHO you are wrong (but I am not an electrician BTW) a true three phase welder has three transformers, using the three sinusoidal waves, ok it is united as one lump, so therefore it not a simple transformer. It also can be connect 'star' or 'delta' and the waves travel through it in a 'figure 8' fashion and its output is united by the rectifiers as one smoother dc voltage. At 150 hz I think.
A single phase welder is a simple transformer whether it be 240 or 415v because it only uses one wave, at 50 hz

Do you mean when the primary side of the tramsformer is wired star and the secondary is wired delta?

 

[normspanners]

Do you mean when the primary side of the tramsformer is wired star and the secondary is wired delta?

No whether the primary is wired star or delta ie series or parallel to determine the voltage on the three (various tapped by the voltage adjuster switch) primaries.
On this particular welder the secondary is fixed star so it is a choice of whether it is connected delta -star or star-star

 

[piman]

Hello Norman,

surely the internal transformer connections are irrelevant as the manufacturer will bring out the connections to terminals, 415 or 220 in this case as it seems to be a dual voltage machine and should be clearly marked? However, I would say the primary needs to be in star for 415 and delta for 220, just like a dual voltage motor.

Single phase 415 is simply that two phases connected to a transformer so it is single phase, one phase does not become a neutral.


Alec

 

[carbon]

Not an electrician either. The welder I use can be used on 230v single phase, 230v three phase or 460v three phase ( information in manual) but internal connections and buss bar links have to be changed to accommodate these different voltages. Primary side of the transformer in parallel for 230v and in series for 460v

 

[Fintray]

Thanks for your reply,
But I am sorry IMHO you are wrong (but I am not an electrician BTW) a true three phase welder has three transformers, using the three sinusoidal waves, ok it is united as one lump, so therefore it not a simple transformer. It also can be connect 'star' or 'delta' and the waves travel through it in a 'figure 8' fashion and its output is united by the rectifiers as one smoother dc voltage. At 150 hz I think.
A single phase welder is a simple transformer whether it be 240 or 415v because it only uses one wave, at 50 hz

The only safe way to connect the welder to the mains, whether 240 or 415 is via the designated connections indicated by the manufacturer as they will have put the correct tappings into the transformer to allow this.
The DC voltage would not be at 150Hz as it is DC rather than AC which cycles between + and - at a regular frequency, nominally 50Hz in the UK.

 

[madkayaker]

My miller is delta wired. Could be either as the centre point of a star wound transformer is neutral point due to the phases being 120 degrees out of sink there is always a difference in potentioal between highest and lowest phase. You would need to consult the wiring diagram to find out for your welder.



As for a connection point of view it's fairly irrelivent as the links are inside the transformer so you only have the three phases and most likely three terminals.

 

[normspanners]

Single phase 415 is simply that two phases connected to a transformer so it is single phase, one phase does not become a neutral.

Thanks but surely it must alternate between live - neutral- live and at the point it passes through the centre of the wave it is a neutral.

The only safe way to connect the welder to the mains, whether 240 or 415 is via the designated connections indicated by the manufacturer as they will have put the correct tappings into the transformer to allow this.

I am not contemplating connecting anywhere else than its normal posts, but a transformer is not the same as a motor in star delta because a motor produces rotary energy and may need star- delta to adjust the torque to start, whereas a transformer produces voltage and is just designed to work at a voltage, whether that be 240 or 415, The Guy was saying that it could be connected star or delta like a motor. I was saying it should not be wired either way in this country it should ONLY be wired to accommodate 415v

The DC voltage would not be at 150Hz as it is DC rather than AC

Sorry I meant it would have 150 pulses into the rectifier bank that is why a three phase welder is smoother than a single.

As for a connection point of view it's fairly irrelivent as the links are inside the transformer so you only have the three phases and most likely three terminals.

there are 9 terminal studs and movable links and I have no manual.

 

[Fintray]

Norm, what make and model is it as someone on here might have a manual?

 

[madkayaker]

I see what you trying to find out now. I would jumper for 415v (or closest to that voltage) try the welder and see what the output voltage is in comparison to what the spec plate says you should get. If there is insufficient excitation of the transformer then voltage will be to low on output so try a lower voltage.

 

[normspanners]

Norm, what make and model is it as someone on here might have a manual?

I have tried, its a hobart rc350 iirc
my other concern is it has a separate single phase transformer, which I would think would need to be connected 415 or 240 but is all loomed up I suppose I could bell it out,This is to run the circuit board and if that is wired incorrectly it will poss double the voltage to the circuit board.
Am I right though that you would not connect it 240 3 phase in this country though because we are 415 3phase ?

 

[Fintray]

You could connect it 240v 3 phase if you converted from 240v single phase first if it has the correct tappings for that. The circuit board transformer would likely be connected to one of the 3 phases and neutral to give 240v.

 

[madkayaker]

We don't have 240v three phase we have 400v three phase (when measured it's normally 415v) American three phase is normally referred to as 220v but that's due to being measured each phase to earth rather than between phases so in truth there three phase is 380v ish. I don't know how common neutral is on there three phase kit so carnt say what the single phase transformer would need. All the kit that I have wired that's been American hasn't had a neutral but as that very high power radio transmitters (200-500 amps a phase) I'm not sure about the little stuff. Bell it out and see where it's connected would be a good start

 

[normspanners]

We don't have 240v three phase we have 400v three phase (when measured it's normally 415v) American three phase is normally referred to as 220v

Thanks MK, That is EXACTLY my point you CANNOT just willy nilly throw wires at it, in case you are putting 415 where 240 should be and effectively doubling the voltage at the PCB correct me if I am wrong but older equipment is critical on input voltage not like modern switch mode gear.
This is my whole point that the welder would never be used on 240v in UK
A motor is not likely to suffer if it is connected star or delta because it will just rotate and release the energy in mechanical terms

 

[normspanners]

You could connect it 240v 3 phase if you converted from 240v single phase first if it has the correct tappings for that. The circuit board transformer would likely be connected to one of the 3 phases and neutral to give 240v.

Thanks I dont quite follow 'the converted from 240v SP bit'
BTW there is no actual neutral post and the cable that looks org is 4 core sy
The fan motor is SP cap start.

 

[Spark plug]

Thanks I dont quite follow 'the converted from 240v SP bit'
BTW there is no actual neutral post and the cable that looks org is 4 core sy
The fan motor is SP cap start.

My welder is the same just 3 phase and earth input. It will have an extra transformer inside with 415v 2 phase input and 240v 1 phase + neutral output, this will be used to supply the single phase equipment, pcb's, control equipment and like you say the fan.

Lots of 3 phase equipment dose not have a neutral input so a transformer is added to supply a neutral, this helps keep the phase balance.