hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Anyone have a link you can share showing the sine waves for 120/240 3-phase delta power?
Thanks,
HWS
Thanks,
HWS
Sine wave
- Thread starter hardworkingstiff
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physis
Senior Member
Re: Sine wave
Here's a three phase.
It comes from this site.
Here's a single phase.
And it comes from here.
I thought I'd be able to find some better material but it wasn't as easy as I expected. I'm sure there are some good animations out there somewhere. The animations I did find were a little too cheesey to bother with.
Here's a three phase.
It comes from this site.
Here's a single phase.
And it comes from here.
I thought I'd be able to find some better material but it wasn't as easy as I expected. I'm sure there are some good animations out there somewhere. The animations I did find were a little too cheesey to bother with.
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Re: Sine wave
Isn't that a 3-phase wye?
I thought a delta would look different since two phases are 120 volts to neutral and the high leg is 208.
Isn't that a 3-phase wye?
I thought a delta would look different since two phases are 120 volts to neutral and the high leg is 208.
- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: Sine wave
If you measure line-to-line anywhere along the conductors (be they branch circuits or transmission lines), you cannot tell if the source is wired WYE or DELTA. The 3-phase graph that physis provided is representative of any set of 3-phase line-to-line voltages, or any set of line-to-neutral voltages from a 3-phase WYE source. But I?m not sure what a set of line-to-neutral voltages would look like for the configuration you have described.
If you measure line-to-line anywhere along the conductors (be they branch circuits or transmission lines), you cannot tell if the source is wired WYE or DELTA. The 3-phase graph that physis provided is representative of any set of 3-phase line-to-line voltages, or any set of line-to-neutral voltages from a 3-phase WYE source. But I?m not sure what a set of line-to-neutral voltages would look like for the configuration you have described.
Re: Sine wave
Stiff,
The three phases are always separated by 120 degrees whether you have a wye or delta, whether you are measuring phase voltages or line voltages.
The high leg 208V you mention would be at a different angle and lower amplitude, but this is not pure three phase.
I am confused by your reference to a neutral in a delta system. Do you mean the 120/240V neutral?
Rattus
[ June 25, 2005, 12:21 PM: Message edited by: rattus ]
Stiff,
The three phases are always separated by 120 degrees whether you have a wye or delta, whether you are measuring phase voltages or line voltages.
The high leg 208V you mention would be at a different angle and lower amplitude, but this is not pure three phase.
I am confused by your reference to a neutral in a delta system. Do you mean the 120/240V neutral?
Rattus
[ June 25, 2005, 12:21 PM: Message edited by: rattus ]
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Re: Sine wave
In a building that has a 120/240 three phase service with a high leg, I assumed the 208 (high leg) to neutral would have a higher amplitude than the two 120 legs. I also assumed the two 120 to neutral legs would be 180 degrees out from each other, not 120. This leads me to believe a sine wave graph of the two 120 volt legs would look like a single phase service, and I could not imagine what the 208 leg would look like in this graph.
LOL, I find that I have a difficult time communicating questions and ideas more and more. Sorry for the confusion, let me try again.
In a building that has a 120/240 three phase service with a high leg, I assumed the 208 (high leg) to neutral would have a higher amplitude than the two 120 legs. I also assumed the two 120 to neutral legs would be 180 degrees out from each other, not 120. This leads me to believe a sine wave graph of the two 120 volt legs would look like a single phase service, and I could not imagine what the 208 leg would look like in this graph.
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Re: Sine wave
Yes.
jwelectric
Senior Member
- Location
- North Carolina
Re: Sine wave
Stiff
You are correct in that a 240 delta would be 180 degrees out of phase with each other as referenced to the grounded (neutral). Draw a delta transformer and tap the ground. The ground is then 90 degrees out of either phase. 90 plus 90 equals 180, or it breaks the middle of 180 degrees.
This configuration there will be a point in time that both voltages will be zero at the same time.
Stiff
You are correct in that a 240 delta would be 180 degrees out of phase with each other as referenced to the grounded (neutral). Draw a delta transformer and tap the ground. The ground is then 90 degrees out of either phase. 90 plus 90 equals 180, or it breaks the middle of 180 degrees.
This configuration there will be a point in time that both voltages will be zero at the same time.
Re: Sine wave
Stiff,
Let the diagram represent delta phase voltages as follows:
Va = 339Vpk*sin(wt + 0) or 240Vrms @ 0 deg.
Vb = 339Vpk*sin(wt + 120)or 240Vrms @ 120 deg.
Vc = 339Vpk*sin(wt + 240)or 240Vrms @ 240 deg.
Now let the "A" winding be center tapped.
The two 120V legs relative to neutral are:
V1 = 170Vpk*sin(wt + 0) or 120Vrms @ 0 deg.
V2 = 170Vpk*sin(wt + 180) or 120Vrms @ 180 deg.
The 208V leg is:
V3 = 294Vpk*sin(wt + 90) or 208Vrms @ 90 deg.
That is, V3 lags Va by 1/4 of a period, while Vb lags Va by 1/3 of a period.
Maybe Sam will draw us some more diagrams.
Rattus
Stiff,
Let the diagram represent delta phase voltages as follows:
Va = 339Vpk*sin(wt + 0) or 240Vrms @ 0 deg.
Vb = 339Vpk*sin(wt + 120)or 240Vrms @ 120 deg.
Vc = 339Vpk*sin(wt + 240)or 240Vrms @ 240 deg.
Now let the "A" winding be center tapped.
The two 120V legs relative to neutral are:
V1 = 170Vpk*sin(wt + 0) or 120Vrms @ 0 deg.
V2 = 170Vpk*sin(wt + 180) or 120Vrms @ 180 deg.
The 208V leg is:
V3 = 294Vpk*sin(wt + 90) or 208Vrms @ 90 deg.
That is, V3 lags Va by 1/4 of a period, while Vb lags Va by 1/3 of a period.
Maybe Sam will draw us some more diagrams.
Rattus
physis
Senior Member
Re: Sine wave
My sine wave capability is limited to a difficult to manage approximation. I think if I try to build a three phase sine wave the results would be below my acceptable quality standards.
Maybe I'll see what I can do later.
Edit: But I can't think of anything I'd put together that wouldn't look like the two at the top.
[ June 25, 2005, 05:43 PM: Message edited by: physis ]
My sine wave capability is limited to a difficult to manage approximation. I think if I try to build a three phase sine wave the results would be below my acceptable quality standards.
Maybe I'll see what I can do later.
Edit: But I can't think of anything I'd put together that wouldn't look like the two at the top.
[ June 25, 2005, 05:43 PM: Message edited by: physis ]
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Re: Sine wave
Thanks all.
Rattus, I drew what you wrote, I SEE
Thanks all.
Rattus, I drew what you wrote, I SEE
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