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Wiring Buck Transformer with GE transformer Help!

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Connect H1 to H3.
Connect H2 to H4.
Connect H2 & H4 to X1.
Connect X2 to X3.
Connect the line voltage across H1 and X4.

Use your AC voltmeter and verify ~103 VAC from H1 to X1. If you've got it, you're done. Connect your load across H1 and X1.

If instead you've got ~155VC...
Connect H1 to H3.
Connect H2 to H4.
Connect H2 & H4 to X4.
Connect X2 to X3.
Connect the line voltage across H1 and X1. Verify ~103 VAC from H1 to X4.
 
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You are limited by the secondary current, since all of the current is passed through it. So at 12Volts you should be able to connect up to 20.8 amps. You have to use both secondaries in parallel, as well as both primaries in parallel.

The transformer is going to be a 12VAC X 20.8 amps or 250VA. With the secondaries in series you'll get 24VAC at 10.4 amps and still 250VA. The transformer is always going to be a 250VA.
 
I think Zigzagflux is the guy who understands this topic well. He posted on the last buck autoformer question here: http://www.diyaudio.com/forums/tubes-valves/133843-how-wire-buck-transformer.html#post1672593

I've done a dozen or so buck or boost transformers (single phase and 3 phase) and the drawing in this link is not the proper way to wire it. You want to wire the primary HV winding in parallel with the line in, then wire the secondary LV winding in series with line (either in phase for boost, or out of phase for buck).
 
Transformers are most flexible; you can use them any number of ways, and there is more than one way to skin a cat.

Both methods will work. My preference is with Ty's connections, which are based on my prior recommendations in the linked thread. A number of reasons:

1. Ty's connection applies 124V to a winding set rated nominally for 144V, so you run with lower volts/turn, therefore lower flux, therefore lower radiated magnetic fields. Benefit for audio systems depending on where the xfmr is located. Pwr's connection applies 124V to a winding rated nominally for 120V. Not exactly a huge problem, but it is what it is.

2. Ty's connection results in total I/O capacity of 1292 VA; Pwr gives you 1032 VA. Check my math; I'm good at making mistakes.

3. Ty's connection produces 103V output, which with a little load current and transformer impedance, will give enough voltage drop to get you exactly at 100V. Pwr's connection produces 99V output, with voltage drop you get below the requested 100V.

Pick your poison, but I see little disadvantage to Ty's connection.
 
I am putting this transformer at the wall. The 100V output goes to the wall outlet.

Can the transformer be hooked up all the time?
Do I need to install a fuse?

When I leave for a few days or if there is a storm, I switch the breaker off.
 

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Those connections will be just fine, and yes, you can leave it energized forever if you like.

As far as fusing, the transformer would be rated for 10.4 A on the primary, which follows Table 450-3(b) as requiring 125% protection, so 13A. Pick the next highest device, so your breaker or fuse is to be 15A. Make sure the neutral is your common connection at H2-H4.
 
Since it is 250VA rating, does this mean that I can use it up to 2500VA? Someone said that when you connect a transformer as a buck, the rating is multiply my 10.
DeathRex said:
You are limited by the secondary current, since all of the current is passed through it. So at 12Volts you should be able to connect up to 20.8 amps. You have to use both secondaries in parallel, as well as both primaries in parallel.

The transformer is going to be a 12VAC X 20.8 amps or 250VA. With the secondaries in series you'll get 24VAC at 10.4 amps and still 250VA. The transformer is always going to be a 250VA.

This is incorrect.

GE didn't list this p/n in the 2007 catalog (the one on my shelf), however, it appears to be identical to the current 9T51B0107. Assuming it is so, and I see no information to doubt it, then the Buck-Boost Selection Tables are a help here. The tables don't assume anyone wants to buck to 100V, however they provide data for boosting 100V to 120V. This connection scenario will give you the same VA capacity as the buck connection. According to Table 4 on page 8-58, that configuration is good for 1.3kVA.

Good luck,

Stuart
 
Thank you guys for the help.

As far as fusing, the transformer would be rated for 10.4 A on the primary, which follows Table 450-3(b) as requiring 125% protection, so 13A. Pick the next highest device, so your breaker or fuse is to be 15A. Make sure the neutral is your common connection at H2-H4.

Just to make sure I understand this right, since the transformer is on a dedicated line and I have a 15 amp breaker, I wouldn't need a fuse?
It's either breaker or fuse but not both is required?
 
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Ummmm,

Serious code violations here. The most egregious being soldering and splicing wires without an enclosure and putting the splice into a combustible wall.

Do whatever you want with cord-and-plug connected DIY or modified equipment. But you are altering a premises system and in the process introducing electrical hazards.

My only advice is to put the electrical system back the way it was (licensed electrician!) and create your 100VAC system as a cord-and-plug connected sub-system.

Stuart
 
Breaker is my recommendation, and is all that is required.

The consumption is very low (it's only a 250VA unit run at low V/Hz) but it can be difficult to measure. Excitation current is highly lagging, which means only a portion of the whole actually contributes to watts loss that you pay for. I wouldn't fret over it, definitely less than a kid's night light.

Might have to provide a picture of the installation to answer the last question; soldering power connections tends to be frowned upon. Code requires a soldered connection be mechanically crimped sufficiently such that the solder is really not necessary. Heat shrink could be rated for 300V, but then again it's not something you really see all too often. Electrical wiring and devices are designed on purpose to avoid solder and supplemental insulation.
 
I remove all the wire splices out of the wall. I put the all the wire splices in the transformer compartment and in the wall outlet housing. I also removed all heat shrink and most of the soldering. I used wire nut for all termination.

Thank you all very much for the help.
 
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