ARmy Rumour SErvice

Single phase is given as the maximum peak voltage 110 (US) or 240 volts (UK). Obviously it will move through it sinusoidal wave this value will decrease and at one point invert.

For triple phase there is a 120 degree space between each of hte three phases, thus whilst one is at a higher point the other two will be much lower or in reverse. In UK three phase is usually rated at 415 Volts (three varying supplies up to 240), in the US about 208 Volts (three varying supplies up to 110).

I am not completely sure of the colour codes now, as they have been changed a few years ago. But hte old stuff is still out there in the walls.

Wasn't it Black, Brown, Black, Blue and Green? I always thought it bonkers that you had two the same. I think now they have changed one of the Blacks.

But to be honest, if you just running the cables across your workshop then regardless of colour, as long as you use a correctly ampped cable (ie it wont melt under use) and you enusre that L1 on the tool goes to L1 on the supply then you will be fine. Is it is plug or will you have to connect to lugs each time?

IIRC correctly the Yanks have a couple of systems, including one where pretty much anything goes. But the colours are Red, Black and Blue for the Live connectors, white is neutral and green is earth.

That said, if you ever open a 3 phase box be prepared for those colours to be different. I think the way they work it is if you have a Red wire it goes on L1, that would never change. But hten if you don't have aBlack then as long as the colour you use isn't used on a nother phase, you can use it as L2. So you could use puce.

Bonkers mate. I'd make sure you get a US sparky in to look at three phase for anything really.

Thanks for the reply CF. I'm confident I can get the saw up and running. I bought it used, the seller had it running in his shop on a 240V supply the same as mine. However, when I first used it in anger, it's bogged down in a piece of plywood. No way, no how should 3/4" plywood bog down a 5hp, 4KW motor. The symptoms indicated under voltage. Motor spins up, albeit slowly, but stalls under load. On checking the wiring box on the motor, it's wired for 460V. No wonder he sold it, thinking it was crap.

The reason I posted this is that there is no neutral. The phases must be either referenced to ground or each other. That makes sense, because in US house wiring, the 120V is actually provided from a center tapped 240V supply, neutral on the center tap. Thus you get two legs of 120 in the house, and the breaker/fuse panel is laid out with two vertical banks. So my single phase input is both legs of the 240V supply.

I was just trying to get it straight in my mind, and reconcile this star/delta thing. Thinking about it, I must have delta, with the load in each phase (ie motor coil) between two points of the delta. In star wiring, the coil must sit between the phase and neutral. I think I just answered my own question.

One last one. What was the voltage output of a military 3 phase genny, say a 16/24 or 20KW? If the answer is 380V, I believe I've got it straight in my heed. It's been a long while since I did 3 phase theory, and cricket bat soldering.

Off the top of my head teh voltage OP of a military gene is 415 Volts, which would be the same as three phase from UK mains... if they weren't providing the same voltage OP then there would have to be some sort of drama when equipment was connected to mains.

IIRC German 3 Phase isn't 415 volts, but 380, so I don't know if you're getting confused with that. There were certain vehicles you'd have possibly been familiar with that had a switch inside to take either 415 or 380 inputs, but I believe gene sets usually chucked out 415. You've probably never seen the switch that enabled this change, as it always had hazard tape over it and people thought flicking it would cause the box body to melt or something.

Some 3 phase systems lack a neutral return, but they are connected to a load taht is balanced. In this way the power flows down one of the other Live legs on their negative cycle. Should there be an unbalanced load then this would be bad... thus the neutral acts like a sort of overflow conductor for this.

I would imagine that a 3 phase motor, as it is on the same axle, would be a balanced load (although I have to admit my experience in that regard is nil, I've always used neutrals).

If your drill was set to 460 volts then that would certainly cause dramas in the power and is probably why it was jamming in simple cuts... hopefuly this hasn't damaged the unit!

Surprised your house doesn't have a neutral, as a house is surely an unbalanced load? But I am not going to get too in to the American house and power system, I'll assume the yank sparky knew what he was doing.

Yes, 415 rings a bell now you mention it. I do know the boxes you're talking about, (sadly!). 380V in GE would make sense, as would the switchover switch, so you could run them in the garages from domestic power. I do recall a certain Scottish ED at 7 wiring up the (fucking huge) feed cable to the SW wrongly and causing all manner of mayhem at both the gene and the load end.

As regards US wiring, the center tap provides the neutral for the 120V sockets, but for the few 240V sockets, they don't necessarily have a neutral. Some do, like the dryer socket, it needs 240V for the motor/heater, and 120V for the control electronics. The ACU doesn't though, it just needs a boatload of current. Same in my shop. Single phase machine tools are generally reconfigurable for either 120 or 240V operation. Higher voltage means less current, less I2R loss, so that's what I go with. This new beast of a saw is the only 3 phase machine I have, it can be either 230 or 460V. But no neutral conductor for either. Having discovered the 460V fubar last night, I wanted to wait until today to rewire it, to let the BFO capacitors discharge. Made that mistake before!

Ok, didn't realise the yanks did 240volt sockets... I know they usually have switched and fused boxes for their tumble dryers and other mahoosive loads, but I've never sussed their love of 110 either tbh. Mainly for the I2R problems as you mention and the ampage increase.

I reckon once you've set it correctly and then wired it up (correctly) you'll have no more problems. TBH.