After finding a pretty old thread here, it provided much sought after info. I have a t-former from an APC 2000 ups, `430-1215` and so far I've identified primary and secondary and using the low AC volt input on the secondary to help identify windings ratios was a super tip!

It also generated a question, if the primary side has white, black, yellow and blue. With the yellow and blue being for buck/boost purposes, how were they actually used?
I can send 120vac into the white/black primaries and get a hair over 16vac on the secondary. So should I be able to feed 120 into the yellow, or blue? When I was testing with an 18vac transformer I could feed that into black/yellow and get 17.5vac, or black and blue and get something like 3vac. But if I try sending the full 120 into black/yellow the lights dim and the strips breaker pops.

If anyone can explain that it'd be super appreciated.

 

You can find out what the relationship of the yellow and blue connections have to the black/white winding by measuring the resistance of every wire to to every other wire. I suspect that the blue and yellow wires are taps on the primary, maybe for higher and lower input voltages.

 

You can find out what the relationship of the yellow and blue connections have to the black/white winding by measuring the resistance of every wire to to every other wire. I suspect that the blue and yellow wires are taps on the primary, maybe for higher and lower input voltages.

Yup, ohmed them all out earlier.. I don’t know what to make out of it. What exactly does the amount of resistance mean?

 

Or I guess I should say.. I know the amounts of resistance can identify a buck or a boost winding. I just dont know what’s what.

 

Say the multiple primary taps are to provide voltage coverage for 230 to 120 right?
What happens if you tie the primaries together in series? Or maybe feed 120 into the 230 leads? I tried googling this and came up short..

 

What results did you get when you checked the resistances? The values will let us know how the winding is made up.

 

Ok so, 4 pri leads, 2 sec.
Primary:
black
white
blue
yellow

black/blue-0.3. black/wh-0.6. wh/yel-0.6
blue/yel-0.2. black/yel-0.2
blue/wh-0.7

Now from what I can tell the normal main primary winding is black/white, with 18vac supplied:

black/white-2.8vac. wh/yel-2.5vac
black/yel-17vac. wh/blue-2.2vac
blac/blue-9.5vac

Now secondary values extrapolated out on 120vac in (with the help of Chatgpt) should be:

black/white-18vac. wh/yel-16vac
black/yel-113vac. wh/blue-14vac
black/blue-63vac

The ultimate goal here is to find a combination, if possible, where the secondary output is around 35vac. But also, why I can feed 18 or 24 volts into black/yellow but not 120.

 

Measure resistance with no power applied, not voltage.
Do it this way, fill in the boxes with the resistance between each pair of colors.

	Blue	Yellow	Black	White
Blue	0	0.2	0.3	0.7
Yellow	0.2	0	0.2	0.6
Black	0.3	0.2	0	0.6
White	0.7	0.6	0.6	0

The numbers don't quite add up. This could be a result of lack of precision in the resistance readings.

Blue - 0.2 - Yellow - 0.2 - Black - 0.6 - White

 

I could have presented the info better.. I measured both resistance and secondary voltage. I know better than to try measuring resistance with a device powered up
And I use a Fluke 187 from around 2009, might not be as accurate as it should be. But yeah no I was just giving all the info I have at this point, guess I went a little overboard.

 

Ok so, 4 pri leads, 2 sec.
Primary:
black
white
blue
yellow

black/blue-0.3. black/wh-0.6. wh/yel-0.6
blue/yel-0.2. black/yel-0.2
blue/wh-0.7

Now from what I can tell the normal main primary winding is black/white, with 18vac supplied:

black/white-2.8vac. wh/yel-2.5vac
black/yel-17vac. wh/blue-2.2vac
blac/blue-9.5vac

Now secondary values extrapolated out on 120vac in (with the help of Chatgpt) should be:

black/white-18vac. wh/yel-16vac
black/yel-113vac. wh/blue-14vac
black/blue-63vac

The ultimate goal here is to find a combination, if possible, where the secondary output is around 35vac. But also, why I can feed 18 or 24 volts into black/yellow but not 120.

From your resistance measurements, I think that the primary is connected like this:

 

I had a second look at your measurement results and they don't make sense to me. Disregard the diagram I drew. When I checked it against the voltages you measured, some of the measurements contradict each other:

black/white-18vac. wh/yel-16vac
black/yel-113vac. wh/blue-14vac
black/blue-63vac

 

What you have is that black yellow, and blue are what is used for the inverter connections when the UPS is delivering power from it's internal battery. It is not separate from the mains connection because the whole device has no external access connections needing to be separated from the mains.
It does reduce the applications for the transformer, though.

 

What you have is that black yellow, and blue are what is used for the inverter connections when the UPS is delivering power from it's internal battery. It is not separate from the mains connection because the whole device has no external access connections needing to be separated from the mains.
It does reduce the applications for the transformer, though.

Ahh I did not think about what happens when the UPS is delivering power. Interesting.

 

I had a second look at your measurement results and they don't make sense to me. Disregard the diagram I drew. When I checked it against the voltages you measured, some of the measurements contradict each other:

black/white-18vac. wh/yel-16vac
black/yel-113vac. wh/blue-14vac
black/blue-63vac

View attachment 322663

Again though.. those extrapolated values are from a chatbot. I lack the mathematical prowess to determine those manually.

 

Don't depend on a chatbot.
Input low voltage AC on secondary and measure AC voltage on primaries across all possible pairs.

 

What you find is that not all of the transformer windings use the same size wire, so the resistance method can not work.

 

What you find is that not all of the transformer windings use the same size wire, so the resistance method can not work.

If the windings are of different sized wire (which would be very unusual in a single tapped winding) measuring the resistance will not give the voltage ratios of the windings but it will give the sequence of the taps on the winding. The pair with the highest resistance are the two ends op the winding. From that, the resistence from one end of the winding to the other wires will give the sequence of the connections.

 

Don't depend on a chatbot.
Input low voltage AC on secondary and measure AC voltage on primaries across all possible pairs.

But.. so that's exactly what I did. Those were the voltage values I gave as extra info.. back when you asked if it'd ohmed them all out. It's the math to determine what the secondary voltages would be from 120v on the primary that it above me.

 

But.. so that's exactly what I did. Those were the voltage values I gave as extra info.. back when you asked if it'd ohmed them all out. It's the math to determine what the secondary voltages would be from 120v on the primary that it above me.

There is a problem with the voltage measurements that you made. See post #11. The white to yellow and white to blue don't fit in with the other measurements. Try what Mr. Chips suggests in post #15. That will give you the most reliable results. Then we can finally sort it out.

 

There is a problem with the voltage measurements that you made. See post #11. The white to yellow and white to blue don't fit in with the other measurements. Try what Mr. Chips suggests in post #15. That will give you the most reliable results. Then we can finally sort it out.

Ok gotcha.. I did actually go through it twice because I forgot to write the values down the first time. But I'll do it again, no big deal