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Hey everyone, i had a question hope you guys can help. Ive come across 3 phase 208 circuits(3 hots) and single phase (2 hots) circuits. And was wondering what the differences were. I do know that in both line to line = 208v but dont know the differnces between both
 

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We had a 5 page thread on this not too long ago and I'm pretty sure the guy still didn't get it. It's an elusive concept
 

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Ditch Digging Dummy
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We had a 5 page thread on this not too long ago and I'm pretty sure the guy still didn't get it. It's an elusive concept
Did the thread get closed? If not I suggest the op read that thread. There is probably a lot of good information in it. I haven't seen it but between everyone on here there is a lot of knowledge.
 

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You have three phases of electricity all at seperate times being generated. Single phase two wire is just two of those phases. You can use single or three phase loads out of a three phase system. Shall we get into why it's called single phase with two conductors?
 

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Out of curiousity, why is there no difference between single phase 240 where the phases are 180 out and 208 where the phases of a 2 pole circuit are 120 and 240 out of phase? They both operate the same equipment generally without problem
 

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Ditch Digging Dummy
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Out of curiousity, why is there no difference between single phase 240 where the phases are 180 out and 208 where the phases of a 2 pole circuit are 120 and 240 out of phase? They both operate the same equipment generally without problem
There is a difference. The thing is an appliance (let's say a range) has a tolerance for varying voltages. Not every single phase 240 volt service will be exactly 240 volts. Hell my house is actually 228 volts. The further away from the rated voltage of the appliance you are the less efficient it will run. If you go outside its tolerance it may not run at all. We have a 120/208 the phase system at our shop and the range be have in the kitchen there is a 240 volt rated appliance. It cooks properly and that's all I can hope for.
 

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Well if equipment is rated for a certain voltage, the best thing to do is give it that but like you know this isn't always possible. The equipment will work either way because its still seeing a difference in potential. And there is stuff out their that has 10%, 15% etc tolerance level where the required voltage needs to be met within the tolerance percentages.
 

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There is a difference. The thing is an appliance (let's say a range) has a tolerance for varying voltages. Not every single phase 240 volt service will be exactly 240 volts. Hell my house is actually 228 volts. The further away from the rated voltage of the appliance you are the less efficient it will run. If you go outside its tolerance it may not run at all. We have a 120/208 the phase system at our shop and the range be have in the kitchen there is a 240 volt rated appliance. It cooks properly and that's all I can hope for.
To clarify in a different way, 3 phase is 2/3 pi out of phase where as single phase is pi out of phase. Why doesnt that make a difference in how utilization equipment operates?
 

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Ditch Digging Dummy
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To clarify in a different way, 3 phase is 2/3 pi out of phase where as single phase is pi out of phase. Why doesnt that make a difference in how utilization equipment operates?
It's a matter of the transformer used. Comparing a single phase transformer and a three phase transformer is like comparing a Wye transformer to a delta. They are completely different systems and operate differently. I'm trying to think of the best way to easily explain it lol.
 

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Out of curiousity, why is there no difference between single phase 240 where the phases are 180 out and 208 where the phases of a 2 pole circuit are 120 and 240 out of phase? They both operate the same equipment generally without problem
I think you must be referring to 120/240 split phase. That is one single phase both lines are 180 degrees from the center tap (neutral).
It is best for me to imagine wires are points each point has a diffrent potential to the two other points at any given time. I then imagine the phase as a line.

If you draw a trinagle with 3 points and 3 lines you can visualize my reprentation of 3 phase power.To have 3 phases we must have 3 points. If I take two points or two wires I only have one phase becuase I can only draw one line. Likewise a 2 phase system requires 4 points or wires.
A voltage (a phase) does not exist on a single point it can only be between 2 points. You can test this by putting an apprentice on a rubber mat and putting a wire in his mouth (DON'T DO THIS).

There can be no phase angle difference from one single phase becuase you cannot compare something to nothing.
 
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