# Thread: Phase angles and a few transformers

Because some of us have been taught that 120/208 or 120/240 is two phases of a three phase system, not a center tapped single phase system as used in 120 volt transformers in the UK. There is some differences in how the power is calculated and used. Actually, I am slightly wrong in this. If you have a 110/220 or 120/240 type system where you measure line to line as double the voltage of line to neutral, then you more than likely have a center tapped single phase system. However, if you measure and have line to line 208 or 230 and line to neutral 110 or 120, then you more than likely are on a three phase system using two phases. The variance is within the normal operations of most consumer equipment and most people would not ever know the difference in use. But, the harmonics on the neutral are different, and the calculations are different. Not installation calculations but conversion of power calculations.

However, not too sure any of this would help the OP. But, I was taught to call center tapped as two phase as you have a positive and negative phase at same time, compared to three phase. Currently it is simply single phase then three phase as teachings go. But other countries still teach single phase - two phase - three phase.
using two legs not two phases.

single phase is one sine wave, its what you get with two legs whether two ungrounded or one grounded one ungrounded. three phase you have three sine waves, you need three legs. two phase, two sign waves, usually four legs

2. Originally Posted by Wire-Smith
using two legs not two phases.

single phase is one sine wave, its what you get with two legs whether two ungrounded or one grounded one ungrounded. three phase you have three sine waves, you need three legs. two phase, two sign waves, usually four legs

Now let's complicate what you said a little by asking how many sine waves there are in a single phase "split phase" system, and also asking how many 'phases" there is?

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Originally Posted by Wire-Smith
using two legs not two phases.

single phase is one sine wave, its what you get with two legs whether two ungrounded or one grounded one ungrounded. three phase you have three sine waves, you need three legs. two phase, two sign waves, usually four legs
to be totally honest with you, for what I do a lot of in Jamaica it is kinda easier to call USA 240v 2 phase and UK 240v single phase to keep straight about how the devices prefer to be wired... I either need a step up transformer for UK stuff or need to run extra wires for it and watch it for problems when running it in a customers home. Certain brands are fine with wiring as USA 240 is wired, but other brands insist on the step up transformer and others are just so finicky that the customer gets mad about them after a few weeks...
Many of the TV systems will simply plug in with an adapter to the regular wall 110 circuits even though marked for 240... but then cannot be made for the tv signal..lol...

Problems of doing anything in a country where everyone wants to bring stuff from where they have been working for many years and have it work...lol...

to be totally honest with you, for what I do a lot of in Jamaica it is kinda easier to call USA 240v 2 phase and UK 240v single phase to keep straight ...
That is fine for you Adam, but when you post you need to stick to the common terminology used in the US or explain that because it is confusing for many people.

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Originally Posted by kwired

Now let's complicate what you said a little by asking how many sine waves there are in a single phase "split phase" system, and also asking how many 'phases" there is?

Can we PUH-LEEZE not start that up again?

6. Originally Posted by ggunn
Can we PUH-LEEZE not start that up again?
Even I agree. We need at least a few months till we go off on that again.

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Parallel, perhaps the problem is in the machine, not the power to it. A switch in the wrong position, a blown internal fuse, some field control wiring not hooked up correctly, Etc.

It seems to me from your post that you have an L6-30r receptacle, a locking 240 volt rated three prong three wire single phase receptacle. Maybe I did not have enough coffee this morning, however I fail to see how the machine would not start having 240 volts across the line terminals. The only difference your corner grounded 240 has to a split phase configuration is the 240 volts to ground instead of 120, and the requirement for a straight rated 240-volt breaker versus a 120 / 240 rated breaker.

If there is no requirement for a neutral, the machine is not going to care how that 240 volts comes across the line wires, or if the ground was even connected. Also you might have a look at 250.122b, the ground wire seems under sized for your application, however it is not necessary anyway with full EMT from panel to receptacle.

edited to add... It is possible the machine was configured to run at 120 volts at its previous facility.

There may be something as simple as a selector switch inside to change between the voltages. the bad news however is if it was configured to run at 120v and you put 240 to it it may need some repairs before it's going to start.

Welcome to The Forum.
Last edited by JFletcher; 10-22-18 at 02:16 PM.

to be totally honest with you, for what I do a lot of in Jamaica it is kinda easier to call USA 240v 2 phase and UK 240v single phase to keep straight about how the devices prefer to be wired.
Conveniently ignoring 480/240V used in rural areas.

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Originally Posted by jumper
Even I agree. We need at least a few months till we go off on that again.
I just checked the calendar. It is time for 'ground up vs ground down'. November is AFCI breaker month. We have to wait until December before we can do single phase vs two phase.

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Originally Posted by winnie
I just checked the calendar. It is time for 'ground up vs ground down'. November is AFCI breaker month. We have to wait until December before we can do single phase vs two phase.

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