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#127075 - 04/18/01 01:18 AM Transformer Discussion #2
Scott35 Offline

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Registered: 10/19/00
Posts: 2707
Loc: Anaheim, CA. USA

T2a = 3 Ph. Delta pri. to 9 Phase secondary [Delta / Wye / Wye] - Rectifier
X1, X2, X3 = Delta sec. - Y1, Y2, Y3 = Wye sec "A" - Z1, Z2, Z3 = Wye
sec "B"

This image shows a "9 Phase" transformer, which will be used in conjunction with a large UPS system. It feeds the rectifier - hence the name "Rectifier Transformer".

It has three separate 3 phase 3 wire secondary points of connection, one being a Delta connection [X1, X2, X3], the other two being Wye connections [Y1, Y2, Y3 and Z1, Z2, Z3].

Running a rectifier with high frequency makes the DC end [output] a lot more stable, so this transformer takes that approach by using multiple secondaries to feed a 9 phase rectifier [similar to a 6 phase AC motor].

The frequency on the output end of a full wave rectifier using 3 phase AC would be 360 Hz [that's the pulsation frequency].
Using the 9 phase arrangement, the pulsation frequency is increased to 1,080 Hz [360 x 3].
Each 3 phase 3 wire rectifier would use 3 forward [+] current Diodes and 3 reverse [-] current Diodes.

I'm trying to get some info on this Xformer - plus the others - which I'll add to the thread later.

Any comments??

Scott SET

Edited by Scott35 (02/21/13 09:03 AM)
Scott " 35 " Thompson
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#127076 - 04/18/01 04:46 PM Re: Transformer Discussion #2
sparky Offline
Registered: 10/18/00
Posts: 5303
on popping the cover on this beast i can honestly say it would definitly be coffee time!

is this secondary anything like an isolation x-former? i can't find this one in my books!

#127077 - 04/19/01 03:10 PM Re: Transformer Discussion #2

Originally posted by Scott35:
... "9 Phase"
... [similar to a 6 phase AC motor].
Any comments??

I am curious about why you are okay with calling these 6 or 9 phase when the phases are derived from three phase input, but you didn't seem to be okay with calling 240 V (USA) 2 phase because these phases are derived from a single power company phase.

I think it is wrong that 240 V (USA) is referred to as single phase. 240 V (European) should rightly be called single phase, because it is. And it is not the same as 240 V "2 phase" (USA).
#127078 - 04/21/01 10:13 PM Re: Transformer Discussion #2
Scott35 Offline

Broom Pusher and
Registered: 10/19/00
Posts: 2707
Loc: Anaheim, CA. USA
Steve [Sparky],

These Transformer cores which I have shot pics of, are all sitting on pallets and not in enclosures. There's maybe 100+ cores total in this Warehouse. They will be used with UPS equipment.

The Warehouse they are in right now is the [now former] West Coast Distribution Centers for North American Phillips Co.[NAPC], Norelco, Phillips Lighting Division and Advance Transformer, Co.
They are leaving this building this month and moving elsewhere. We have done lots of TI work for these companies at this location and a few others.
They took on some temp. storage deals with numerous contractors, which is why the real neat UPS equipment was stored there.

These are Isolated Transformers, but not Isolation Transformers.
By this I mean that the Primary and Secondaries are Isolated [not electrically connected], but they aren't the typical Isolation Transformer, because they have high voltage Primaries with lower voltage Secondaries.
I'll draw some schematics for these cores and post them in the threads.
There's all kinds of cool cores around this place!!
I'm not sure which books you would have, which would show these types of cores, as they are not of the "Norm". Maybe would be more likely found in Advanced Transformer Connections type books, or more likely in something related to high-end DC Conversion manuals [high power UPS systems would be a good source].
I have them in my Engineering Manuals, but I don't suggest these books to anyone with a social life!!
If you want to take that route, try either:
* Standard Handbook for Electrical Engineers,
* Practical Transformer Design Handbook.


The Manufacturer, along with my Engineering manuals quote them as "6 Phase" or "9 Phase" transformers.
In reality, they are simply Delta / Wye Secondaries for the 6 Phase ones, or Delta / Wye / Wye for the 9 Phase ones.
If the coil winds as opposed to the core flux flow creates a lag / lead in phase time bewteen the different secondaries, then they could be 6 or 9 phase output.
They barely slip by the terms properly by the fact that there's either 2 or 3 separate 3 phase 3 wire secondaries, which are completely separate from each other.
Even then, I find the term to be kind of mistaken too!! Good Call!!

A 6 phase motor will have 2 Delta or 2 Wye wound Stator coils, which are to be connected to two separate 3 phase 3 wire sources. The intent is to have a high frequency equivalent running the motor.
Same thing for the Rectifiers which these multi phase transformers will be connected to.

As for 1 phase, there's absolutely no way to say it would be a 2 phase system.

First off, 2 phase requires two independent phasors, which are 90 degrees out of time [like 3 phase has phasors which are 120 degrees out of time]. The Degree Angle multiplier for Vectors and other calcs = 1.414 [square root of 2], similar to the 3 phase multiplier of 1.732 [square root of 3].

Secondly, the 2 phase system has two separate 2 wire phase outputs, unless it's for the 3 wire system - then one common is made up from "Line 2" from "Phase A" and "Line 1" from "Phase B".
2 Phase systems are normally created from 3 phase 3 wire open Delta "Tee" banks, using Transformers which the Primary and Secondary coils have 87% taps.

Lastly, 2 Phase systems are so antiquated, they only exist in very old sectors of cities like Chicago and Long Beach, CA. [I have seen only one 2 phase 4 wire system in Long Beach].

I could easily make the asumption regarding 6 / 9 Phase systems, rather than even thinking about stating a 1 phase system could be 2 phase. If the windings were done in such a matter to lead / lag one another, then it's going to put out 6 / 9 phase AC from 2 / 3 separate 3 wire secondaries.

Like I said, I'll draw up some schematics in AutoCAD and post them to the threads to describe these cool cores!
If you guys want, I'll draw a couple for 2 phase systems and post them.
I plan to include a bunch of schematics in my website when I get it going, so there's always that approach! Those schematics will cover Xformer connections in great detail, along with Buck/Boost/Choke Transformer connections, Autotransformers, Multi-Secondary 1 phase Transformers, Ballasts [Reactors, etc.], how to determine relative polarity, etc. and - of course - these special use/type Transformers [along with larger and more detailed pics].

Scott SET
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#127079 - 04/22/01 04:18 AM Re: Transformer Discussion #2
sparky66wv Offline
Registered: 11/17/00
Posts: 2232
Loc: West Virginia

If it were 2 phase 180 degrees apart then the two 120 legs would cancel each other out rather than produce 240V...

How does this relate to balanced current on the neutral?
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#127080 - 04/22/01 07:44 AM Re: Transformer Discussion #2
Scott35 Offline

Broom Pusher and
Registered: 10/19/00
Posts: 2707
Loc: Anaheim, CA. USA

Exactly! If there was Two separate Phasors [Sinewaves will also apply] which were 180 degrees apart, they would nullify, or cancel each other out - similar to bouncing a sound wave with an echo of it's own, but at 180 degree phase shift - it will cancel the original sound wave out. This technique is used in Industrial Noise control.

Put two single coil pickups in an 180 phase shift [in parallel], and you have practically no volume, plus that "out of phase" sound.

The Neutral balancing currents for 1 phase 3 wire systems works mainly because the magnetic flow in the core will drive fully across the entire coil in an equal strength.
Where there's an imbalanced current, the magnetic flow in the core will have a higher level from the side of the core which the "Line" with the higher current load is wound from, then to the center of the core.

This occurs when the secondary circuits draw currents from the windings, which changes the stablized level of magnetic flow in the core. The Primary tries to re-establish that steady level in the core by producing more and more flux flowing in the core, until things become stable again.

Easy way to picture the magnetic flow which creates the imbalanced current is to think of only drawing a load from L1 and the Neutral, with no load on L2 and the Neutral.
The magnetic flow in the core will circle around the part of the winding which makeup the L1 and Neutral circuit with a high intensity.

This equals out to have an electrical circuitry setup which is a series current flow with balanced loads, but parallel with the imbalanced portions of loads.

If the loads are equal, they will naturally run in series with the L1 - L2 conductors, simply because it's easier for larger currents to flow this way [easier to drive full current levels through the entire coil].
Any currents which are uncommon to other currents flowing, will be run through the center tap. This would be very common for Harmonic currents and EMI / RFI.

Along with these currents, the currents needed to charge circuits will flow through all taps - regardless if the loads are only across L1-L2 [240 VAC]. There will still be circulation of currents and charging currents on the center tap.

Scott SET
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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