Leyton transformer connections

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winnie

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Recently a discussion of the 'Leyton' transformer connection came up:
http://forums.mikeholt.com/showthread.php?t=182511

The 'Leyton' connection is purported to convert a single phase load into a balanced three phase load.

Hugh Leyton had previously joined the MH forum, but has not been active since joining to discuss the transformer connection:
http://forums.mikeholt.com/showthread.php?t=146298

I took part in an extensive discussion on the topic:
http://forums.mikeholt.com/showthread.php?t=176806

The Leyton connection is similar in concept to the 'zig-zag' connection of a three phase generator to produce single phase output, and is also related to the 'double-delta' connection of a 12 lead generator.

I contend that the Leyton connection will put similar current loading on all three phases of the connected transformers, but that the phase angle of this loading is still _single phase_. As such, I contend that the loading placed on the three phase supply is still _single phase_ loading.

As a simplified example, consider an open delta to open delta three phase transformer, where the 'open jaw' is between terminals A and C. Connect a resistor between terminals A and C. Clearly the full current flows in the AB and BC coils, both primary and secondary. However no current flows out of the B secondary terminal, and only minimal current flows into the B primary terminal.

In any case, I think a discussion about the functionality of the Leyton transformer connection should really be in its own thread, and not cluttering jake.hagm's first thread ;)

-Jon
 
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GoldDigger

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winnie said:
Recently a discussion of the 'Leyton' transformer connection came up:
http://forums.mikeholt.com/showthread.php?t=182511...
I contend that the Leyton connection will put similar current loading on all three phases of the connected transformers, but that the phase angle of this loading is still _single phase_. As such, I contend that the loading placed on the three phase supply is still _single phase_ loading....
Click to expand...

And based on the math and the measurements, I contend that not only is the current equal on all three primary lines, it has essentially the same power factor as the single phase load. That means that each current is closely in phase with the line to neutral voltage.

If there were a substantial power factor error in any of the three primary wires, the kVA at the primary would be substantially different from the load kVA.

Both the math and practical measurements (by Hugh, not by me) confirm that the kVAs match.

Would you also assert that the loading on the three phase side of a Scott-T would still be essentially two phase?

The circuit is somewhat related to zig-zag in that the output phase is not in line with either of the two coils alone, and in zig-zag it is true that the current in each coil is as a non-unity power factor since the series current can have only one phase. That is not the case with the Leyton circuit.
 
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winnie

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Electric motor research
GoldDigger,

Hugh's documented connection is at https://dl.dropbox.com/u/88752751/Transformer for 120-240V from 3-phase - Detailed A2.doc

The connection is clearly a delta to double delta connection, _or_ half of this, with a delta to open delta on one side and a single phase connection on the other side.

The vector math for calculating the voltage appears correct to me, but I don't see math for current.

I'd just ask you to consider the simplified situation (in post #1) with an open delta to open delta transformer, supplying a resistive load across the open jaw. If the open jaw is between terminals A and C, and _nothing_ is connected to secondary terminal B, how much supply current would you expect to flow to primary terminal B?

Say the transformer primary voltage is 480V, the secondary voltage is 120V, and 40A of load current (between secondary terminals A and C) is flowing with unity power factor. What are the 3 phases of primary line current?

Thanks
Jon
 
Electric-Light

Electric-Light

Senior Member
Someone made series of posts on the interwebz in 2012 and that person practically lost interest in it and no third party reference to it. Actually for that very reason Wikipedia declined his attempt to make an entry about it.

https://en.wikipedia.org/wiki/User_talk:Hugh_Leyton
https://en.wikipedia.org/wiki/User:Hugh_Leyton/sandbox


preferable.. presently and general wording really feels like a patent application draft. Questionable problem statements designed to make his concept the solution to this problem isn't really building credibility.

"Presently, it is quite common to supply 120 / 240V from a 3-phase Delta supply, by centre tapping one of the three 240V phase windings. However, this limits each 120V Load to only 5% of the transformer KVA rating and the whole transformer must then be de-rated by 30%. It also leaves one phase High at 208V which can’t be used for any regular purpose, so also unbalances the 3-phase supply. Another alternative is to use a separate Utility Supply for the 120 / 240V from the Utility 3-phase supply. This of course, has problems if a Stand-by Generator is to be used, or if two Meters are not wanted.

Apparently a common alternative is to just connect the 208V supply to all equipment requiring 220V - 240V, this is a very bad alternative, because the 208V at the supply point, will typically be only 195 – 185V at the Air-conditioner terminals and will seriously shorten the life of the compressor motors, it also voids the guarantee on such equipment. Sometimes, the 220V Loads can be supplied from a 208V source, via Boost Transformers. This is good for the equipment, but complicates the Distribution panels, and does not balance the loads across all three phases. Perhaps acceptable, if the 220V Loads are small compared to the whole site loads."


Meanwhile, I am extremely busy buffing out carbon track footprints from rich people's yachts with zero emission equivalent fossil fuel generator powered buffer which makes no emissions because the old geezer's photovoltaic at his house located somewhere i don't even know cancels out emissions on paper.
 
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I

Ingenieur

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he provides no current or power calculations
should be easy to model in simulink
if bored enough I'll give it a shot
 
Electric-Light

Electric-Light

Senior Member
Ingenieur said:
he provides no current or power calculations
should be easy to model in simulink
if bored enough I'll give it a shot
Click to expand...

Why even build something with real things these days? You find additional problems unforeseen in simulation but usually you simulate first and if it doesn't pass, you're wasting money to attempt lab test.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
winnie said:
...
Say the transformer primary voltage is 480V, the secondary voltage is 120V, and 40A of load current (between secondary terminals A and C) is flowing with unity power factor. What are the 3 phases of primary line current?
Click to expand...
10A-0A-10A

Phase angle of primary winding current follows phase angle of secondary winding current at 1 to 4 ratio. Apply KCL at "B" node and you get 0A line current.
 
Electric-Light

Electric-Light

Senior Member
Well so am I still current to believe that to apply single phase load evenly across a three power power, you need something that physically spins or a transistorized recommutating static converter?
 
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wwhitney

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Possibly stupid question: at the subcycle level, can/does an ideal transformer store energy? Or is Pout = Pin instantaneously?

I ask because for a single phase linear load the power delivered is sinusoidal with twice the basic frequency. And I seem to recall that in 3 phase systems, the power delivered to a balanced linear load is constant.

Cheers, Wayne
 
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GoldDigger

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Electric-Light said:
Well so am I still current to believe that to apply single phase load evenly across a three power power, you need something that physically spins or a transistorized recommutating static converter?
Click to expand...
No. You can do it with transformers. That has been the topic of this whole thread.

mobile
 
G

GoldDigger

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wwhitney said:
Possibly stupid question: at the subcycle level, can/does an ideal transformer store energy? Or is Pout = Pin instantaneously?

I ask because for a single phase linear load the power delivered is sinusoidal with twice the basic frequency. And I seem to recall that in 3 phase systems, the power delivered to a balanced linear load is constant.

Cheers, Wayne
Click to expand...
A transformer has Pin = Pout instantaneously as long as you are not considering the magnetizing current, which will be pumping energy into the core and pulling it out again, just like an ideal inductor or capacitor.

mobile
 
Electric-Light

Electric-Light

Senior Member
wwhitney said:
Possibly stupid question: at the subcycle level, can/does an ideal transformer store energy? Or is Pout = Pin instantaneously?
Click to expand...

Any coil stores energy in an amount relating to henries of inductance and amps of current.

I ask because for a single phase linear load the power delivered is sinusoidal with twice the basic frequency. And I seem to recall that in 3 phase systems, the power delivered to a balanced linear load is constant. Cheers, Wayne
Click to expand...

This is true but for reasons not related to your earlier question. A complete ALTERNATING cycle is forward, stop, reverse, stop. The power delivery is on, off, on off. So each cycle delivers power in two pulses and dropping to zero in between pulses. Three phase power has three sets of these shifted in timing by 120degree which fills the valley
 
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GoldDigger

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Electric-Light said:
Any coil stores energy in an amount relating to henries of inductance and amps of current.



This is true but for reasons not related to your earlier question. A complete ALTERNATING cycle is forward, stop, reverse, stop. The power delivery is on, off, on off. So each cycle delivers power in two pulses and dropping to zero in between pulses. Three phase power has three sets of these shifted in timing by 120degree which fills the valley
Click to expand...
And because of the nature of sine waves, the "fill in" is exactly level, not just approximate.
When driving a motor, the key is that the torque is constant. As long as speed is constant, that means constant power delivery.

mobile
 
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