I need help understanding AC electricity and generators (1/3 phase)

[MossRoad]

 

[Industrial Toys]

I have been busy that last few days. Surprised to see such a "simple" matter at ten pages. Have to go back and see "what went so horribly wrong?"

WOW! I did read some of the material. Either I don't hjave a clue, or others don't and I am not being sarcastic.

Phase is a time measurement in RC circuits and a degree thing in rotating fields. I see no such thing in a transformer winding. It might as well be batteries connected in series. You could just think of it as the full voltage across both windings, and then arbitrarily, somone tapped the middle and decided to ground it. It's the potentional across the windings has has nothing at all to do with phase.

Just maybe explained a little different. You have a transformer winding that has 240 volts. You tap the winding in the middle and just for shitts and gigggles, attach that to ground. Now you have 120 time two, volts exactly as you have in your house. Single phase, no phase relationship (180 degrees or otherwise) between the one side of the winding or the other.

 

[CobyRupert]

Semantics.
Let’s say a electrician (or more likely, a homeowner) brings 2 random hot wires and a ground from their panel to their hot water heater. They measure 120v in each wire.
They’re going to discover the two wires connected across the load very much adds up 0 volts or 240V based on the phase relationship of the wires.

 

[grsthegreat]

i cant agree more. Im an electrical contractor and even im bored.

 

[Industrial Toys]

CR. No disrespect intended, but what you said make no sense at all. Sure, at any given point in time, an AC wave goe to zero. How would them putting a meter, lets say across their load give them zero volts? Based on phase relationship? Of the wires? Huh?

 

[CalG]

Single phase motors run "rough" compared to poly phase motors. That is why 3 phase motors are preferred over single phase motors for machine tool applications. Especially grinding.

Single phase power crosses zero voltage twice each cycle. Poly phase supply and motors "overlap" and have no effective "zero crossing"

Have you ever seen a #phase solid state relay? Not likely, 'cause they would never unlatch! ;-)

I know, a bit off theme, but ...

I'm still mystified how any TWO legs of a three phase (120 degree) generator can supply usefull single phase power at anywhere near customary voltage.

Is it the magic smoke? I've seen a lot of that...

By the way, It's AMPS that do all the work, Volts are just the whippers driving the amps through resistance.

 

[Industrial Toys]

Like men are the amps that do the work and women are the voltage that does the nagging, asking, telling, whatever.

 

[strantor]

Have you ever seen a #phase solid state relay? Not likely, 'cause they would never unlatch! ;-)

I have several. They're just 3 triacs in a case with a single input.
Internet example:

I'm still mystified how any TWO legs of a three phase (120 degree) generator can supply usefull single phase power at anywhere near customary voltage.

Not sure the link below will satisfy your curiosity depending on in depth your "how" is, but it will at least show you connection schemes that will yield useful voltages.

https://www.power-tronics.com/help/wiring-diagrams/Terminal-Chart.pdf

 

[CobyRupert]

CR. No disrespect intended, but what you said make no sense at all. Sure, at any given point in time, an AC wave goe to zero. How would them putting a meter, lets say across their load give them zero volts? Based on phase relationship? Of the wires? Huh?

I mean if the two wires from random circuits are off the same “pole”, or “leg” and are “in phase” with each other, a zero phase differential, there’s going to be zero volts across the load.
Only when the phase relationship of the two wires to each other is 180 degrees will they “add” to be 240V.
Again....semantics. There’s only one phase.

 

[Industrial Toys]

Sorry, I still don't understand what you are trying to say. When a single pair of wires comes into your property (Single Phase)to the transformer, nothing about phase relationship is revalent anymore as far as what voltages you see on the premises. That entire secondary winding is all running in unison. Nothing out of "phase" with anything else. You could throw some capacitors in there and THEN you would have varying phase relationships.