220.61 exception

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codequestion

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220.61 (A) exception says for 3 wire 2 phase. Does this include 120/208V single phase derived from trough 120/208v three phase? It would have 2 phase.

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Instead of each one of us grabbing our Code books for all your questions, please take the time to cut-and-paste it into your question. Let's all get on the same page with the exact wording of the exact year Code you are using.

What does "derived from trough 120/208" mean? Is that another typo? These questions would probably be easier and more accurate to ask if they weren't from your phone.

What are you calling 2-phase?
 
MAC702 said:
Instead of each one of us grabbing our Code books for all your questions, please take the time to cut-and-paste it into your question. Let's all get on the same page with the exact wording of the exact year Code you are using.

What does "derived from trough 120/208" mean? Is that another typo? These questions would probably be easier and more accurate to ask if they weren't from your phone.

What are you calling 2-phase?
Click to expand...
Tapped from trough. The 2 phas 3 wire is wording from nec 2014 text.

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codequestion said:
220.61 (A) exception says for 3 wire 2 phase. Does this include 120/208V single phase derived from trough 120/208v three phase? It would have 2 phase.
Click to expand...

No, that reference is for a 2-phase system not single phase from a 3 phase system.
 
codequestion said:
What are these 2 phase system 120/240v or 120/208v?

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A two phase system has at least two phase conductors whose phasors differ by 90 degrees.
It can be two hot and one "neutral" where L1-N is offset 90 degrees from L2-N.
Or it could be four wire "square" with no neutral conductor and 90 degree rotations as you go around the square.
Or it could be a star with four hots and a common neutral.
Or a couple of other unlikely combinations in between. The common thread is the 90 degree phase rotation.
The star configuration can be looked at as two crossed three wire single phase 120/240 systems with both neutrals sharing a wire.
 
GoldDigger said:
A two phase system has at least two phase conductors whose phasors differ by 90 degrees.
It can be two hot and one "neutral" where L1-N is offset 90 degrees from L2-N.
Or it could be four wire "square" with no neutral conductor and 90 degree rotations as you go around the square.
Or it could be a star with four hots and a common neutral.
Or a couple of other unlikely combinations in between. The common thread is the 90 degree phase rotation.
The star configuration can be looked at as two crossed three wire single phase 120/240 systems with both neutrals sharing a wire.
Click to expand...

Nope, I told you all since I have never seen it, do not like it, and is confusing:

Two phase does not exist.

It nothing more than a conspiratorial plot to drive me bonkers......
 
Besoeker said:
Sott and Le Blanc connections are usually two phase.
Click to expand...


I am not as familiar with the Le Blanc, but the Scott-T can be used in either direction to convert between a two phase and a three phase system.
Also interesting is the Leyton connection (http://forums.mikeholt.com/showthread.php?t=172825) which converts only in one direction from three phase to single phase with total balance over the three source phases.
Jumper does not think that one exists either. :)
 
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