415V single phase

[dman]

Thanks Stringy,
It all makes more sense to me now - I just couldn't figure out the 480V thing!
I've got a separate circuit box in the shed - I'll get a sparky to put in a 32A circuit for this and do the back plane changeover to from 415V to 240V.

[cyberhonky]

although the question has been answered, i'll continue on. In a lot of industrial situations, many single phase (240v) machines (mig/tig/arc bandsaws etc) are wired to a 3 phase plug (using only 1 phase). Being metal trade/welding background (possibly the enemy to some here) it was common place at many factories, as it took the load off the single phase circuit, and didnt make the 3 phase circuit work hard at all.

I remember starting early in summer time to get the welding done before the heat, and even on 3 phase circuit you knew when others in the street were starting up their equipment, cause you had to up the juice on your machine to compensate.

As for getting 3 phase at your place, if you tell them its for a welding machine, they'll probably laugh before telling you the answer is 'no', so yeh, go with the voltage change

[chrisp]

To answer the original question, to have 415V single phase, you need two (240V) phases connected to your house (it's quite common).

The phases are 120 degrees apart so the maths is:

(240V at 0 degrees) + (240V at 120 degrees) = 415.7 V at 60 degrees

(You can draw it up as a triangle and treat it like a trigonometry problem.)

You don't need three phases for 415V equipment.

The 480V is typically for SWER (Single-Wire-Earth-Return) installations as used in remote areas (farms and such). There is only one phase supplied, but the pole transformer has a 480V secondary that is "centre-tapped" effectively giving two 240V phases that are 180 degrees apart. You can use a single-phase for the usual 240V gear and a 480V for the higher power gear (such as a welder).

I hope this helps.

Chris

[thatirwinfella]

the train of thought that some of you seem to be stuck in is that there are only two ways of getitng your voltage... 230v single phase of 415v three phase. the 230v is measured to neutral, which is [theoretically] at 0v at all times. that is from any phase, the red white or blue, not some mysterieous 4th pahse used only for 230volts.

415 volts three phase is largely used for motors where the difference between the phases is used to rotate the stator creating motion, but thats another story. the 415 volts in question here is measured across any two phases... red to white, red to blue, blue to white. there will be 415v across these.

thats where this 415v single phase is coming from... it's just like single phase, but rather than being down to neutral it is to another phase.

finally, if you were to measure voltage across three phases simultaneously it would be zero volts... which is where the neutral comes into it. This is also the star point of star wound motors/transformers. delta misses out and doesn't have a point of zero voltage, or 230volts.