Would this be a real neutral?

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Sneaky!

Sneaky!

Imagine a single 120V load between L1 and N. Then half the load current is supplied directly from the 240V source. The other half is supplied by winding L1-N. Check it out.
 
Another thing to consider is size of supply conductors and load to be served. If possible I would try to provide 240 volt supply circuit and install 240 - 120/240 SDS transformer to allow twice the load on the same supply conductors.
 
rattus said:
Imagine a single 120V load between L1 and N. Then half the load current is supplied directly from the 240V source. The other half is supplied by winding L1-N. Check it out.
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Hmmm... please elaborate. I'm not getting what you are describing. :confused:
 
He's saying that, if you used an autotransformer to convert 120/240v to 120v, half of the power would come from each half of the 120/240v supply.

Added: It's another way of saying that higher voltage is one way of delivering more power.
 
rattus said:
Smart,

Give me a basic diagram, and I will draw in the currents for you.
Click to expand...

Now how is that supposed to work? You want me to draw you a basic diagram of something you are describing that I do not get...:confused::confused:

Is the OP diagram basic enough?

If you are describing an autotransformer that is powered by 240V and outputs 120/240, your description is valid... but I have read the entire thread, and I am thinking the gist is using an autotransfomer setup with a 120V supply to get 120/240 with a *real* neutral. Did I miss something along the way???
 
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You are so good at it:

You are so good at it:

Smart $ said:
Now how is that supposed to work? You want me to draw you a basic diagram of something you are describing that I do not get...:confused::confused:

Is the OP diagram basic enough?

If you are describing an autotransformer that is powered by 240V and outputs 120/240, your description is valid... but I have read the entire thread, and I am thinking the gist is using an autotransfomer setup with a 120V supply to get 120/240 with a *real* neutral. Did I miss something along the way???
Click to expand...

The OP's diagram is too cluttered. How about just the CT secondary winding with a single load? Of course I could do it myself, but you are better than I am with graphics. I would then sketch in the currents in order to explain my statement. Fair enough?
 
Here it is :)

step_down_Transformer.jpg
 
ronaldrc said:
Here it is :)

Already done it Smart. Didn't scan it either. Thanx tho.

The crux of the matter is that that V12 is loaded with the series combination of the actual load and the same load reflected through the autotransformer. Note also that the two halves of the load current flow in opposite directions in the two halves of the primary.
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Rattus

I don't know if this is your point or not?

But we could use this to our advantage as a trick to use say #12/2 nm romex to feed your
garage with 240 volts with only two wires.

Then if you had a device powered at 120 volts it could be as large as 40 amps.instead of 20 amps.

Advantage being you can use #12 instead of #8 conductor to power a 40 amp. 120 volt machine or device.

And I also have 240 volts with a neutral that we created.

Your single device can be as big as 40 amps.or say 30 amps and also have enough
power for 120 volt lighting and a duplex recpt. also.

This is really a good advantage.

Please excuse me for cluttering your diagram :D




Rattus'_step_down_Transformer2.jpg



But then we might have to drive a ground rod? :mad:
 
ronaldrc,

This would violate NEC Rule 215.11 which prohibits deriving a feeder from an autotransformer unless the supplied system has a grounded conductor that is electrically connect to a grounded conductor of the supplying system.
 
ronaldrc said:
Then if you had a device powered at 120 volts it could be as large as 40 amps.instead of 20 amps.

Advantage being you can use #12 instead of #8 conductor to power a 40 amp. 120 volt machine or device.
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That's why the power company does it, and to a much greater degree.
 
LarryFine said:
That's why the power company does it, and to a much greater degree.
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Yes and a whole lot bigger differrential.

I remember when I worked part time here at the VA center as a Electricians Helper.
The whole Va. center was on a three 100 amp. fuses of course were talking 35 years ago.

Now its probably on three services of about 200 amp. fuses per service drop. :)
 
ronaldrc said:
Rattus

I don't know if this is your point or not?

But we could use this to our advantage as a trick to use say #12/2 nm romex to feed your
garage with 240 volts with only two wires.

Then if you had a device powered at 120 volts it could be as large as 40 amps.instead of 20 amps.

Advantage being you can use #12 instead of #8 conductor to power a 40 amp. 120 volt machine or device.

And I also have 240 volts with a neutral that we created.

Your single device can be as big as 40 amps.or say 30 amps and also have enough
power for 120 volt lighting and a duplex recpt. also.

This is really a good advantage.

Please excuse me for cluttering your diagram :D

Rattus'_step_down_Transformer2.jpg



But then we might have to drive a ground rod? :mad:
Click to expand...

Ronald, this is what I thought you meant in your first post. It seems you already have a neutral unless you only have a 120V service to your house.
 
Help needed

Help needed

ronaldrc said:
This is a way of getting a neutral from a 120 volt circuit,how many would call it a real neutral?

Create-120, 240-with-a-neutral.jpg
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I'm having a mental block with this diagram. How is 120v achieved on line two, there is no induction occurring is there? And would line one and line two be 180 degrees apart??
 
mark32 said:
I'm having a mental block with this diagram. How is 120v achieved on line two, there is no induction occurring is there? And would line one and line two be 180 degrees apart??
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Yes, there is. It's a single core, so any single winding, when energized at its design voltage, will cause all of the other windings to be energized at their design voltages (losses aside.)

The unconnected 480 winding will indeed have 480v between its terminals. And yes, relative to the neutral, the L1 and L2 could be considred to be 180 deg. out of phase.

Read my post again; #18 in this thread.

Added: Keep in mind that power isn't free. For every amp used by the 240v output (L1-L2), two amps will be used by the primary (again, with losses ignored.) A 120v load added to either L1-N or L2-N will be seen as 1:1.
 
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First, thank you Larry for directing me towards this thread and secondly for shedding some light on this subject, you've altered the way I look at how transformers work, thanks!
 
Rattus

Know when I posted the first diagram thats what I was illustrating making 120/240 out of
120 volts and recreating a neutral.

The reason I asked about the neutral being a real neutral was once you drop one of the line conductors with single phase the white conductor is no longer technically a neutral.That being the neutral or white conductor coming from the house.

When I seen your 240 verson I liked it even better.

For thoses who don't understand this study about the Zig Zag transformer, this is just a single phase verson of it.

Mark

Larry is right it has to be wound on the same laminated steel core of the transformer to work.It is the same as one winding with a center tap, to work as the autotransformer.

You are thinking right you will not get this effect with two transformers.
There is no phase shift here everything happens at same time, you can get a polarity change from the primary to secondary of course we are not using it. :)
 
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