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

[TractorGuy]

Panels are divided in half. Two legs are required. One half has 120v and the other half has 120v. The contacts are staggered so one leg connects to every other contact from top to bottom. 240v breakers use one leg from both sides.

 

[strantor]

I beg to differ on the 120/240 being out of phase. AGAIN, someone confuses the issue. If they were 180 degrees out of phase, they would cancel each other out. They are simply different taps, or windings, on a single phase.

Or am I totally misinformed? I'm not an electrical engineer and this stuff, the math, has never been my strong point.

Single phase IS single phase. Not suddently two phases! Not on a generator and not in your house panel.

Agreed, Thanks. I thought my bicycle analogies were pretty clever, but I guess not.

 

[Mat4644]

No - See the diagram on post 13. It's all single phase. The two 120 volt sources are 180 degrees out of phase from each other and this creates the 240 volt differential. At the sine waveform peak one is 120v plus and the other 120v opposite peak creating a 240 volt differential.

Incoming single phase AC power is fed into a center tap transformer , reduced and split into two 120 volt single phase lines that are 180 phase degrees apart (polarity inversion). This is then fed into your house service. This is why it's called split phase.

 

[Mat4644]

Google how center tap transformers work and the polarity inversion relationship between windings.

 

[strantor]

No - See the diagram on post 13. It's all single phase. The two 120 volt sources are 180 degrees out of phase from each other and this creates the 240 volt differential. At the sine waveform peak one is 120v plus and the other 120v opposite creating a 240 volt differential.

This is why it's called split phase.

Just because you were able to screenshot evidence of someone else on the internet that shares your misconception, doesn't make either of you correct. Whoever typed that up is also trying to teach the rest of us that a 120VAC wave has peaks of +/- 120V. They need to educate themselves about RMS voltage before continuing to speak publicly.

A single phase supply has ... (one)... phase. What is that one phase 180 degrees apart from? Itself?

 

[Mat4644]

I am correct. Look at the RMS potential of a single 120v sine wave in the diagram and since there is a second wave with the voltage inverted power and voltage are doubled if the load is across both. You'd be surprised how many career electricians don't have a clear understanding of this.

I am a retired electrical/electronic technician with an EE degree and numerous certifications. 44 year career.

 

[strantor]

You'd be surprised how many career electricians don't have a clear understanding of this.

Yes, I am. Even many EE don't understand.

What is (-120) + 120? I'm referring to the sum of these supposed "180 degrees out of phase" 120V-pk (84VAC (RMS)) waves that are supposed to combine to make 240V at times T1 & T3.

 

[strantor]

This is easier to understand if we think of it like a DC circuit. At the risk of further muddying the waters with two batteries which I'm sure someone will fixate on as two separate voltage sources (two phases), here's an illustration:



Please (please) consider these two batteries as inseparable, or as a single battery with a center post (like a center tapped transformer).

If we are referencing from ground to each end post, then our multimeters will give us one positive value and one negative. If we want them both to read positive, we can simply reverse the leads of the first multimeter. In fact, we should reverse the leads because we've got them backwards. The leads should be arranged the way that the batteries are arranged.

From here all we have to do is make the batteries reverse polarity 60 times per second, and it turns into AC example.

The only source of this "180 degrees out of phase" (revered polarity) waveform is some dingus who do doesn't connect their oscilloscope properly (or can't because they're using a non-isolated scope and don't know how the invert button works).

 

[Mat4644]

Yellow is the RMS potential of sine wave E1 - A load applied on E1 can utilize this power -120v
Red is the RMS potential of sine wave E2 - A load applied on E2 can utilize this power - 120v
Green is the RMS potential of a load applied across E1 & E2 - 240v

 

[strantor]

Yellow is the RMS potential of sine wave E1 - A load applied on E1 can utilize this power -120v
Red is the RMS potential of sine wave E2 - A load applied on E2 can utilize this power - 120v
Green is the RMS potential of a load applied across E1 & E2 - 240v

View attachment 667038
View attachment 667039

Ok I've drawn the batteries "180 degrees out of phase" (reversed polarity) as you think a split phase system works.



What will meter "C" read?

This is a pictographic restatement of my question that you didn't answer.

What is (-120) + 120?