I found an AC Power source finally after going through a box of AC-DC wallwarts I'ce collected. I remembered I have a 24v AC Transformer used in a Coffee Roaster controller and loosened a couple twist caps to access the 12-0-12 volt taps (yellow-black-yellow). In the coffee roaster I use yellow-yellow which provides 24VAC output.

Testing Step-up function:
All testing was into the primary side (heavy 10ga wire) of the UPS Transformer to test the voltage out of the 4 secondary winding wires.

Using 12v input:
UPS Transformer secondary wires 1 & 3 output 100 volts

• -wires 1 & 2 output 1 volts
• - (deflection on tester stayed at same pt even while scale changed from 500v-50v-10v)
• -wires 1 & 4 output 1 volts
• - (same as 1&2)
• -wires 2 & 4 output 12 volts
• -wires 3 & 4 output 0 volts
• - (no movement)

Using 19v input (transformer output of 24v dropped to 19v under load of the UPS transformer connection)
-UPS Transformer secondary wires 1 & 3 output 150 volts

Now, how do we interpret the readings above to guestimate expected results when testing Step-Down function with power into the four side secondary wires?

Which wire input combination yields a low voltage, high amperage output on the primary side?

 

I tested from the Step-Down side, it appears to be a 10:1 on Secondary Leads 1&3 to the primary side output. 12V In yielded 1.1V out. 24V In yielded 2.5V out.

So extrapolation suggests that 110v house Mains In will yield 10-12v out. I have a LUTRON Dimmer to decrease the 110v IN to a level providing the approx 2v needed for the 15ga Nichrome wire to heat to 600 degreesF.

 

one and three are the mains in. 120 on one and three gets you 13 .8 vac. on the big black and big white wire

with mains on two and four (another primary) got me 11 vac on the big black and big white wire.

One and three also have the fuse.

 

The checking method described does seem to work out quite well. No destruction, and the ratios were determined and the results are adequate proof. I am not sure that the Lutron dimmer will deliver the results that you want, but give it a try. There will be waveform distortion, so check the transformer to see if it starts getting hot, which is the warning that something is wrong.

 

I have one of these and this puzzled me at first too. What we have here is a transformer
with a main primary winding that uses just the black and white wires . But the blue yellow
wires provide a buck or boost function so you can adjust for low or high line voltage. For
example if I just use the black and white wires I get 14vac output but connecting the yellow
wire to the black wire and applying line voltage across the white and blue wires I now have
12.4vac and if i had fliped the polatity of the blue yellow wires i would have gotten about 15.5v .

 

I have one of these and this puzzled me at first too. What we have here is a transformer
with a main primary winding that uses just the black and white wires . But the blue yellow
wires provide a buck or boost function so you can adjust for low or high line voltage. For
example if I just use the black and white wires I get 14vac output but connecting the yellow
wire to the black wire and applying line voltage across the white and blue wires I now have
12.4vac and if i had fliped the polatity of the blue yellow wires i would have gotten about 15.5v .

Buck/ boost transformers have been around for a while and they are a great way to deal with locations that have supply voltage problems. Unfortunately they can be a bit confusing to those who don't know what they are. The one that you have would allow adjusting the input voltage to a series regulator to keep the dissipation down.

 

If it is a transformer there would be different gauge windings.
Can you see the windings ?
Can you measre the resistance of the windings ?

I once got few of those from a 1.5KVA APC slim type UPS and they turned out to be just inductors....

The white and black with fuse are your 120 in. I did not use blue & yello. The output is 13-13.8 volts on the big black and white on my transformers.

 

The white and black with fuse are your 120 in. I did not use blue & yello. The output is 13-13.8 volts on the big black and white on my transformers.

The buck/boost wires are always the same size as the primary wires, because they handle the same current. But this seems like a new thread starting, probably it should be a new thread, if it needs to keep going.

 

E209188 or APC UPS's transformer has four on the primary side and two wire on the secondary side.
There is no centre tap on the primary side. Although they are marked as "tap".
They are just a tap from primary side for battery charging ( may be).
1. Neutral
2. tap 15v
3. hot
4. tap 12v
more info here

 

Any transformer can be used Buck/Boost, as long as the power requirement is observed for the buck/boost winding.
In this instance, the winding current is identical to any other type of transformer
Max.

 

E209188 or APC UPS's transformer has four on the primary side and two wire on the secondary side.
There is no centre tap on the primary side. Although they are marked as "tap".
They are just a tap from primary side for battery charging ( may be).
1. Neutral
2. tap 15v
3. hot
4. tap 12v
more info here

This was very informative & interesting. I found another interesting way to test the transformers by feeding 15VAC into the low voltage side and then measuring the stepped up primary like in the clip below (watch from 10:39).

 

I have done exactly that: Fed a low voltage into a transformer winding that I presumed was low voltage and measured the voltage on the other connections. One hint to get accurate results is to measure the input voltage instead of presuming that it is what you intended. The voltage ratios will be very close to the turns ratios, and each winding resistance will give some clue as to the current capability.

 

OK, Moderator. The link appeared in my incoming mail and I did not notice that the thread was old. That happens a fair number of times. It is a real pule because I do not go exploring old threads. So it is not clear to me how his happens.

 

It happens if someone, even with spam or other post that subsequently gets deleted, posts a response and you are subscribed to the thread (which, by default, happens automatically when you reply to one).