Single Ph. 208 /120 Transformer One-Line diagram--stuck on details

[Besoeker3]

Absolutely you DO!

You have a three phase Y system, just the voltages are higher than we use here in the US and Canada, or lower (as in 277/480 Y or 347/600 systems).

Ignore the "We do not have 120, etc.".

You have 230 from phase to neutral and 400 between phases, right? What you are missing is a whole selection of appliances and other large loads for sale at the local store that use single phase 400. If you needed to wire a 400 volt single phase stove (range, cooktop, dryer) you would put each wire to a phase. Simple. That's what we do with large appliances, put them on two phases to get SINGLE PHASE! It is one sinewave. Therefore single phase.

Our three phase system follows the same physics rules that your three phases do.

Except we don't. A single phase range, cooker, or dryer is 230V. Not 400V.

 

[wwhitney]

Except we don't. A single phase range, cooker, or dryer is 230V. Not 400V.

Right. Frank's point is that if 400V single phase equipment were commonly available in the UK, then it would be easily supported by changing a 230V 2-wire service to a 230/400V 3-wire service. Fundamentally, your 400Y/230V 3 phase is the same as our 208Y/120V 3phase other than a factor of (almost) 2 in the voltage.

So with regards to the 120/208V single phase service, your comment "we don't have that here" is not true in the sense of "our electrical system wouldn't support that" (or the analogue of it). Rather it's that "that's not something we choose to do as we don't have 400V single phase loads that would require it."

Cheers, Wayne

 

[Besoeker3]

Right. Frank's point is that if 400V single phase equipment were commonly available in the UK, then it would be easily supported by changing a 230V 2-wire service to a 230/400V 3-wire service. Fundamentally, your 400Y/230V 3 phase is the same as our 208Y/120V 3phase other than a factor of (almost) 2 in the voltage.

So with regards to the 120/208V single phase service, your comment "we don't have that here" is not true in the sense of "our electrical system wouldn't support that" (or the analogue of it). Rather it's that "that's not something we choose to do as we don't have 400V single phase loads that would require it."

Cheers, Wayne

Yes so 208/120 isn't single phase.

 

[wwhitney]

Yes so 208/120 isn't single phase.

It's called 120/208 to distinguish it from 208Y/120 wye 4-wire, I believe.

It's a voltage system with 2 phases that is used only to supply single phase loads. So the common term for it is single phase. Now if you wish to confuse people by using a technically-more-accurate-but-contrary -to-common-usage term for it, that's your choice.
Cheers, Wayne

 

[Besoeker3]

It's called 120/208 to distinguish it from 208Y/120 wye 4-wire, I believe.

It's a voltage system with 2 phases that is used only to supply single phase loads. So the common term for it is single phase. Now if you wish to confuse people by using a technically-more-accurate-but-contrary -to-common-usage term for it, that's your choice.
Cheers, Wayne

I'll stick with the accurate version.

 

[wwhitney]

I'll stick with the accurate version.

In the interests of actually communicating with other people, you'd be better off registering your objections with a phrase like "so-called single phase" or maybe "wye-derived single phase". Two phase is generally understood to be a system with two phases at 90 degrees phase shift, not 120 degrees, and is still in use in the parts of the US.

Cheers, Wayne

 

[Besoeker3]

In the interests of actually communicating with other people, you'd be better off registering your objections with a phrase like "so-called single phase" or maybe "wye-derived single phase". Two phase is generally understood to be a system with two phases at 90 degrees phase shift, not 120 degrees, and is still in use in the parts of the US.

Cheers, Wayne

Yes, I well am aware of that.
And I am not really objecting.
Just commenting on the UK/European simpler system.

 

[Frank DuVal]

Except we don't. A single phase range, cooker, or dryer is 230V. Not 400V.

That is exactly what I said! You do not have a store down the street selling a 400 volt single phase appliance.

 

[Frank DuVal]

Yes so 208/120 isn't single phase.

It is as far as the load is concerned. Load is two wires, therefore single phase. One sine wave present at load.

 

[Frank DuVal]

Simpler? You mean fewer choices? Ha!

About the only choice missing here in North America is a 100 VAC system. Or 50 Hz. We got rid of 25 Hz years ago.

We have used equipment from the UK and had to reset our generator to 50Hz. The Caterpillar tech says "that engine doesn't sound right. Oh, right, 50 Hz..."

 

[Besoeker3]

It is as far as the load is concerned. Load is two wires, therefore single phase. One sine wave present at load.

Consider the 208/120 phase angles. They are not in the same straight line.

 

[LarryFine]

L1-N = 120v 1ph
L2-N = 120v 1ph
L1-L2 = 208v 1ph

There is no equipment that will care about the phase angle, which only manifests itself as a voltage difference.

 

[Besoeker3]

L1-N = 120v 1ph
L2-N = 120v 1ph
L1-L2 = 208v 1ph

There is no equipment that will care about the phase angle, which only manifests itself as a voltage difference.

Fair point.

 

[kwired]

That is exactly what I said! You do not have a store down the street selling a 400 volt single phase appliance.

They don't have multiwire appliances either, like our 120/240 ranges and dryers, their equivalent would be if they had one that had 400 volt single phase elements but at same time other loads within same appliance that are 230 volts. Probably just doesn't happen. Might see 400 and 230 volts in same industrial machine, 230 being for control items more so than major load items? May be separately derived within the machine majority of the time as well though, similar to North American machines having 480 input but a 480 x 120 control transformer.

 

[Frank DuVal]

There is no equipment that will care about the phase angle, which only manifests itself as a voltage difference.

Right, Larry, hence why it is 208 volts instead of 240 volts! If you look at the 208 volt wires (two wires), you will only see one sine wave, just like you see on your 230 volts (2 wires), just less voltage.

Same as in England you do not see 460 volts using two of the 230 volt wires.....

 

[Besoeker3]

Right, Larry, hence why it is 208 volts instead of 240 volts! If you look at the 208 volt wires (two wires), you will only see one sine wave, just like you see on your 230 volts (2 wires), just less voltage.

Same as in England you do not see 460 volts using two of the 230 volt wires.....

And in other parts of England...............................