XPost: alt.home.repair
From: null@void.com
On 12/3/2013 6:28 PM, Salmon Egg wrote:
> In article<529e1008$0$49510$c3e8da3$fdf4f6af@news.astraweb.com>,
> bud-- wrote:
>
>> On 12/3/2013 8:25 AM, trader4@optonline.net wrote:
>>>
>>> And I'm still waiting for an answer why a system with
>>> two phases that differ by 90 deg is acknowledged by everyone to have two
>>> phases. If they differ by 240 deg, that's two phase right? If they
>>> differ by 170 deg, that must be two phases, right? So, what magically
>>> happens when they differ by 180 deg that suddenly there are no longer two
>>> phases? And how do the electrons know?
>>>
>>
>> For a garden variety split-phase supply (240/120V from a transformer
>> with a centertap) are there 2 "phases"?
>
> The above post and other replies indicate that knowledge is more
> important than jargon. In terms of poly phase jargon, think of a
> symmetrical 4-phase system with neutral. What we call 2-phase really is
> a subsystem of two adjacent phases. Two opposite phases give you an
> Edison system. You can get other such combinations.
The specific question is whether in US distribution, split phase
240/120V has "2 phases", phase A and phase B?
Is the centertapped secondary "single phase"?
When "phase B" is negative "phase A" does it make sense to talk about 2
phases?
>
> In principle, as long as you have at least two phases other than
> completely in-phase (three or four wires) or completely out of phase,
> you can use transformer combinations to give you any phase combination
> you like. The Scott T-connection happens to be the one that converts
> between 3-phase and 2-phase (adjacent phases of a 4-phase) system.
>
Relatively small 480/277V to 208/120V wye transformers sometimes use 2
transformers with a Scott connection. The transformers operate at true
2-phase.
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