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240/120 vac 50 amp coach power

Yahoo Message Number: 67098
Hi Coach Owners,

A few owners took part in the subject discussion ? msgs 66998- 67080, 10 msgs so far.
Two things stood out in the explanations that perhaps need further clairification.
First.

Globally, power (energy) transmitted is normally three phase. Locally, residential power delivered is mostly single phase.
Second.

Coming from the transformer to the residence or coach where it is single phase, the two 120 vac legs with neutral and safety ground (tied together in your circuit breaker box) ARE 180 degrees out of phase with each other.
The link below provides the explanation in the last to sketches.
http://www.allaboutcircuits.com/vol_2/chpt_10/1.html
You can also find two photos in the Photos section, titled 240 vac 50 amp phasing, showing the hookup used to display on a Flukescope the two 180 degree out of phase voltages.

Fred Kovol

2000 Allure 30593

Re: 240/120 vac 50 amp coach power

Reply #1 –
Yahoo Message Number: 67107
Fred and all,

Let my start by indicating that this reply is directed to a number of members that seem interested in the discussion. I'm sure that does not represent the majority of the members so this would be a good time to use the infamous 'delete key' and please accept my appologies.
Referring to the link below, I spent 40 years dealing with power distribution as a distribution engineer. I have never heard the term 'split phase' applied to a single phase 120/240 volt service. In fact I have never heard of the term 'split phase' at all.
The article is an example of what I like to call back door engineering (my term). First the author tries to establish the point by starting at the 120 volt level and working backward to the source transformer. You must always look at the system from the source to the load not the other way. Second he tries to falsely establish a phase relationship based merely on the instantaneous negative and positive values of the voltages. This is a figment of the author's imagination and simply is not true. Note that the only 'phase angle' established is strangely either 0 or 180 degrees. That is because there is actually only one source phase voltage namely the 240 volts. The fact that it is divided in half by tapping the center of the single phase transformer secondary still leaves only one basic voltage and it or any parts of it can not by definition be out of phase with itself. It takes two source voltage of different phases coming from the generation source and that simply is not present in a single phase service.
A mention has been made of a 120/208 volt service. That is a 2 phase service and yes the 208 or high/hot legs are at an angle of 120 digress to each other and all of the phase angle math now applies. Not that it doesn't apply to the single phase voltages. The 0 and 180 degrees simply cancel out.
Some have mentioned power factor and inductive/capacitive load. Yes that can cause the current to lead or lag the voltage by some angular degree but it is a power factor angle not a phase angle.
If you draw the 240 volts as a vector it is a straight line of what ever the volts/inch scale of your drawing. Now place a point exactly half way on that line. Now if you believe that the top half of the line is pointing 180 degrees in the opposite direction to the bottom half then you are of one philosophical school of thought. If you believe that both ends are pointing the same way then you are of a philosophical school of thought that agrees with the math of power engineering. You need two lines, not one, to be at an angle with each other.
Ok Fred as you requested. Anyone that wishes further discussion please contact me off line. Enough of it.

Don Seager

2004 Allure 31046

Hi Coach Owners,

A few owners took part in the subject discussion ? msgs 66998- 67080, 10 msgs so far.
Two things stood out in the explanations that perhaps need further clairification.
First.

Globally, power (energy) transmitted is normally three phase. Locally, residential power delivered is mostly single phase.
Second.

Coming from the transformer to the residence or coach where it is single phase, the two 120 vac legs with neutral and safety ground (tied together in your circuit breaker box) ARE 180 degrees out of phase with each other.
The link below provides the explanation in the last to sketches.
http://www.allaboutcircuits.com/vol_2/chpt_10/1.html
You can also find two photos in the Photos section, titled 240 vac 50 amp phasing, showing the hookup used to display on a Flukescope the two 180 degree out of phase voltages.

Fred Kovol

2000 Allure 30593

Re: 240/120 vac 50 amp coach power

Reply #3 –
Yahoo Message Number: 67132
Fred Once in for All Thanks for putting this to Bed, I praise you! I was going to test each and everyone of you and if you fail off to WORK you go I dont want to get out of retirement for this! Ken Retired Cat Power Systems Tech! 99 Allure 30356

Re: 240/120 vac 50 amp coach power

Reply #4 –
Yahoo Message Number: 67141

I agree with you Fred. If there was no phase difference between the two hots then the currents would add on the neutral not subtract. I don't intend to prolong the agony, BUT, if there is a transformer guy out there...... would there not be a difference in the position of the sine wave from one output of a transformer to the other output with a center tap neutral?

Dave

aka Billy Byte (trusty hound)
2000 Allure #30443



Quote
>

Hi Coach Owners,

A few owners took part in the subject discussion - msgs 66998- 67080, 10 msgs so far.
Two things stood out in the explanations that perhaps need further clairification.
First.

Globally, power (energy) transmitted is normally three phase. Locally, residential power delivered is mostly single phase.
Second.

Coming from the transformer to the residence or coach where it is single phase, the two 120 vac legs with neutral and safety ground (tied together in your circuit breaker box) ARE 180 degrees out of phase with each other.
The link below provides the explanation in the last to sketches.
Quote
>http://www.allaboutcircuits.com/vol_2/chpt_10/1.html > > You can also find two photos in the Photos section, titled 240 vac 50 amp phasing, showing the hookup used to display on a Flukescope the two 180 degree out of phase voltages.

Fred Kovol

2000 Allure 30593
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Re: 240/120 vac 50 amp coach power

Reply #5 –
Yahoo Message Number: 67151
?
Dave,

I agree with you also but the position of the sine waves relative to each other is not caused by a difference in phase. There is only one phase present in the circuit. If the transformer is connected between Phase 1 and the neutral on the high voltage then the phase present is also phase 1 on the secondary side relative to the source generation.
To have any angle present in the circuit that is due to phasing you must also have one or both of the other two phases present Phase angles in a power system are created by the source generation. You can not invent a phase angle difference merely by looking at polarity differences. Reactive load will cause the current to lead or lag the voltage but the current is not out of phase with the voltage. The power factor angle in not a phase angle.
The result would be exactly the same if the power source were 120/240 volts DC. I truly hope that no one out there is willing to talk about voltages in a DC circuit as being 180 degrees out of phase.

Sorry folks. My bad. I broke my promise.

Don Seager

2004 Allure 31046

Re: 240/120 vac 50 amp coach power

Reply #7 –
Yahoo Message Number: 67154
DON SEAGER presented it correctly. Others don't know how to use a scope. BOB

Re: 240/120 vac 50 amp coach power

Reply #8 –
Yahoo Message Number: 67160
There exists some major disagreements about this subject. Let me start by saying that Fred Kovol is correct. Consider this. His input contains the only one that gives a pictorial and mathematical explanation. Everyone else, including me, inputted verbiage that may have some terminology problems. For most RVers the exact technology is not meaningful. Note that all the inputs contrary to that offers neither a pictorial or mathematical explanation of their position. So I would challenge them to mark up the inputs from Fred if they disagree. Input a published reference that supports their position. Give us a picture or sketch that shows their position. Give us a picture or sketch of what the scope waveforms should look like.
Independent of terminology the last picture on Fred's reference would be represented on an oscilloscope as two sinusoidal waves, one displaced 180 degrees of if phase angle terminology offends you when one has a maximum peak the other would have a minimum peak and the zero crossing would remain the same.
I would suggest that if the real answer is important to you, don't take our word for it. Go to your local library, Barnes and Noble or local technical school or University and research it for yourselves.

Joe

98 Intrigue

Re: 240/120 vac 50 amp coach power

Reply #9 –
Yahoo Message Number: 67184
While this subject has been beat to death, let me say I think Fred is correct too. I don't care what someone has done for a living, I like references and data backing up their argument. Further, when someone starts describing an engineering point as "philosophical" I turn off. Fred Koval has, over the years, been a prime and competent contributor to this forum.
BTW, I know something about the subject myself. You can, by having a center tap transformer, break a singe-phase into two phases, 180 degrees out of phase. Look at the two legs on an o-scope, and that is what you will see. I don't care if the power originated at the source as a single phase. A person with an o-scope cannot tell the difference between a singe phase split by a center tapped transformer and two phase originated at a power source. It is just electrons moving in a wire, folks.

Al Colby

2000 Intrigue 10979
 

Re: 240/120 vac 50 amp coach power

Reply #11 –
Yahoo Message Number: 67203
Ken Retired Cat Power System here, Fred you are 10000 percent correct. I did not spend 1973/2008 working on Power Generation without School and knowledge of Voltage, Currant and Phasing! Your photo is correct. I had generators thet were single phase and three phase, I wont go there as this is beat to death. Thanks for showing to the group your fluke meter showing real time sine wave. Like me let the rest of the group believe their own electrical law's. We are Blessed to have Talants like yours on our group. BTW I have parallelled many a generator up to two mwgawatt in sets of many up to 4160 three phase I had most of the major hospitals in 13 countys in South Florida! Im off my soap box. Guess we should start a power system group! LOL. Ken 99 Allure 30356