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Old 06-11-2016, 07:30 PM   #1
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Default 3 phase transformer single phase supply

My boss asked me a question, and I could not satisfactorily explain what would happen if you hooked a three phase transformer to a single phase supply. For the sake of this conversation we assumed the transformer would be delta 240 to wye 480 as the suggestion was for step up. I told him it would be horribly inefficent but to be honest I was only using supposition.
Could some of you guys enlighten me about the physics of this situation?
Could you use this setup as a single phase transformer?
What output could you expect at the secondary conductors?
Would a delta delta transformer provide you with different results?
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Old 06-11-2016, 07:41 PM   #2
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Single phase in can only give single phase out.
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Old 06-11-2016, 07:47 PM   #3
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I am with P&L with that and it can work but not the best way at all ...

That sorta a ( loosely used term ) backwood rig up i know i did used that for emergecy only but for perament useage just get single phase transformer and be done with it...
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Old 06-11-2016, 07:49 PM   #4
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Quote:
Originally Posted by Ultrafault View Post
My boss asked me a question, and I could not satisfactorily explain what would happen if you hooked a three phase transformer to a single phase supply. For the sake of this conversation we assumed the transformer would be delta 240 to wye 480 as the suggestion was for step up. I told him it would be horribly inefficent but to be honest I was only using supposition.
1 Could some of you guys enlighten me about the physics of this situation?
2 Could you use this setup as a single phase transformer?
3 What output could you expect at the secondary conductors?
4 Would a delta delta transformer provide you with different results?
1 - I am not sure what you are asking here, please be a little more specific ? Are you asking about efficency ?
power out equals power in plus losses, so yes efficency has to be accounted for.

2 - almost any thing to anything is possible if you use the correct transformers and connection configurations.

3 - again almost any voltage is possible.

4 - Yes.


Your questions lack specifics, electricians like to be very specific,
so if we have not answered your questions please be more specific.

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Old 06-11-2016, 09:51 PM   #5
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You cannot get 3 phases from a single phase with only a transformer.
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Old 06-11-2016, 10:04 PM   #6
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I think the bigger question is why did your boss ask you that?
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Old 06-11-2016, 10:42 PM   #7
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In your case, you'd have 240/480 out with 240 in. No 277 and no 3.

If you were to connect a capacitor from one 240 leg to the unused transformer phase, you'd have 3 on the 480 side. Sort of.......

Since this would the a tuned capacitive/reactive circuit, the voltage on the manufactured leg would vary with the load.

This is how a rotary phase converter works except the rotor and stator in the pony motor will tend to balance voltage more than a simple transformer would.
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Old 06-11-2016, 10:53 PM   #8
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In your case, you'd have 240/480 out with 240 in. No 277 and no 3.

If you were to connect a capacitor from one 240 leg to the unused transformer phase, you'd have 3 on the 480 side. Sort of.......

Since this would the a tuned capacitive/reactive circuit, the voltage on the manufactured leg would vary with the load.

This is how a rotary phase converter works except the rotor and stator in the pony motor will tend to balance voltage more than a simple transformer would.
So suppose no capacitor, would this work?

I am trying to see how this works as they are all interconnected right? Don't the primary phase windings connect to the suffixed terminal of the next phase winding?

If so, how would this work? It isn't that same as three single phase transformers being used for a three phase system right, as those would act independent of each other?

My thinking has to be off on this...
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Old 06-12-2016, 12:14 AM   #9
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Micromind assuming we do not care about any manufactured 3 phase and only are looking for a hick single phase transformer. Would you have the 480 single phase between the x1 x2 terminals what would the voltage be between the x1 and x0 termials?
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Old 06-12-2016, 12:16 AM   #10
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Micromind assuming we do not care about any manufactured 3 phase and only are looking for a hick single phase transformer. Would you have the 480 single phase between the x1 x2 terminals what would the voltage be between the x1 and x0 termials?
It is an interesting question... with a 240-480 there is a 2:1 ratio, but on this idea, I am at a loss.
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Old 06-12-2016, 12:19 AM   #11
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Some of you guys wonder why I would ask. The reason I ask is becuase I told him it would be a terrible idea, yet as proffesional the way in which we sell our knowledge is just as important as the content of that knowledge. I found myself to be lacking in both catagories on this subject. Thus the wide net I cast for information. If any one has information on Flux and saturation in thos situation I would appriciate that as well. I found the usual resources online to be underwelming.
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Old 06-12-2016, 12:32 AM   #12
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Quote:
Originally Posted by dmxtothemax View Post
1 - I am not sure what you are asking here, please be a little more specific ? Are you asking about efficency ?
power out equals power in plus losses, so yes efficency has to be accounted for.

2 - almost any thing to anything is possible if you use the correct transformers and connection configurations.

3 - again almost any voltage is possible.

4 - Yes.


Your questions lack specifics, electricians like to be very specific,
so if we have not answered your questions please be more specific.

1 I am asking what the electrical and magnetic forces in this situation would produce as observable results.

2 the question contained the restraints of a 240 to 480 delta wye transformer.

3 see two.

4. Indeed.

The fact that my queation lacks specifics is merely the result of my ignorance. It takea knowledge to form good questions.

Thank you for your reply i am sorry if my clarifications appear snide. I can assure you that they are not meant to be it is just a caveat of the medium.
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Old 06-12-2016, 12:40 AM   #13
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Maybe the better question is "Can single phase power be converted to three phase power?". The answer is yes with a phase converter or maybe a VFD-Variable Frequency Drive. As stated earlier you can't make the conversion with just a transformer.
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Old 06-12-2016, 12:44 AM   #14
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Originally Posted by Bird dog View Post
Maybe the better question is "Can single phase power be converted to three phase power?". The answer is yes with a phase converter or maybe a VFD-Variable Frequency Drive. As stated earlier you can't make the conversion with just a transformer.
I don't think that is the question though. It is not about converting 1ph to 3ph with a transformer.

It is about what would be the voltage and how would it react when a single phase supply is connected to a 3ph Delta transformer...

I originally thought he was speaking Delta/Delta but now I think he is thinking Delta/Wye?

Either way, how does it react and why?
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Old 06-12-2016, 12:59 AM   #15
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Quote:
Originally Posted by Bird dog View Post
Maybe the better question is "Can single phase power be converted to three phase power?". The answer is yes with a phase converter or maybe a VFD-Variable Frequency Drive. As stated earlier you can't make the conversion with just a transformer.
As switched said that is not the question.
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Old 06-12-2016, 01:00 AM   #16
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You're right. I wanted to bring up something that could be applied in the real world as the question seems purely theoretical. It's like putting a Ford clutch in a Chevy truck and asking how much transfer of power will there be even though they are mismatched.
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Old 06-12-2016, 01:14 AM   #17
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I have to backtrack here a bit. In my original post, I thought the transformer was ∆-∆ but it's not. It's ∆-Y. This changes things a bit.

If it were ∆-∆, then single phase 240 in would result in single phase 480 out. One of the coils would have 240 on it, the other 2 would have 120 because they are effectively connected in series because single phase has 180 phase shift.

In a ∆-Y transformer, in this case, 240∆ to 277/480Y, each coil is 240 on one side and 277 on the other. Since one of the coils is operating at full voltage, you'd have 277 from lets say X1 to X0. Since the other 2 coils are effectively connected in series, you'd have half voltage (138) from X2 to X0 and X3 to X0 but there's be 0 volts from X2 to X3.

This is because of the 180 phase shift. If it were connected to a 3 source, there'd be a 120 phase shift and voltage would appear from X2 to X3.
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Old 06-12-2016, 01:21 AM   #18
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I have to backtrack here a bit. In my original post, I thought the transformer was ∆-∆ but it's not. It's ∆-Y. This changes things a bit.

If it were ∆-∆, then single phase 240 in would result in single phase 480 out. One of the coils would have 240 on it, the other 2 would have 120 because they are effectively connected in series because single phase has 180 phase shift.

In a ∆-Y transformer, in this case, 240∆ to 277/480Y, each coil is 240 on one side and 277 on the other. Since one of the coils is operating at full voltage, you'd have 277 from lets say X1 to X0. Since the other 2 coils are effectively connected in series, you'd have half voltage (138) from X2 to X0 and X3 to X0 but there's be 0 volts from X2 to X3.

This is because of the 180 phase shift. If it were connected to a 3 source, there'd be a 120 phase shift and voltage would appear from X2 to X3.
A lot to ask.... can someone map this?

I understand on a 3ph to 3ph Delta how it works, but on 1ph to 3ph as suggested, you would not have a 240v leg and then two 120v legs would you?

I may be confused on what you said.... I need it mapped out I think...
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Old 06-12-2016, 01:48 AM   #19
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So you have a transformer that is 240V Delta/480V Y, and you want to connect 240V single-phase to two of the primary terminals?
If you can remove a link somewhere to break the delta circuit, then you will have 480V single-phase from one of the secondary windings and very little from the other two.
If you leave the delta circuit intact then I think you get 1 x 480V and 2 x 240V secondary windings. Could be useful, yes?
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Old 06-12-2016, 10:20 AM   #20
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I think the bigger question is why did your boss ask you that?
In many firms "bosses" often are better business men than electricians, Nothing wrong with that, you can hire knowledgable electricians.
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