UPS Transformer ?!? Specifications - Power Supply?

This is my first time to post on this particular forum.

Welcome.

I acquired a transformer that is purposed to meet those requirements but I have some doubts

I have some doubts from looking at the pictures. A 16V 50A (800VA) transformer is physically quite large, and this looks a little too small for an 800VA transformer. What are the physical dimensions of the transformer?

What do you think?

Sounds like an autotransformer.

Link

This is quite common to have a primary with a number of taps to allow adjustment of the output voltage. Unfortunately as this appears to have come out of a UPS it is likely going to be difficult to find any data on it (being likely a custom-made transformer).

Do you know what UPS it came out of? It may very well be from an offline/standby UPS which uses the transformer just for charging up the UPS batteries, not for powering the UPS load directly (meaning the transformer will be substantially smaller than the power rating of the UPS).

Link

A 50A output would need about 6-gauge wire. That might give a hint. The scale is hard to determine, but this transformer doesn't look that large. Too bad the data on it are meaningless; one would think they should include primary/secondary voltages and volt-amp capacity.

The laminated core of the transformer measures 4 1/2" across the top, 2 1/2" wide and 3 3/4" high. It's quite heavy, I would guess without actually weighing it to be around 15 pounds. The smaller leads are about 16 gauge and the other two leads coming out of the other side are about 12 gauge. The inline fuse is rated at 15 amps.

You are right about the limited about of information available on UPS transformers. They are custom made (many of them by Chuan Shun Electric Industrial Company Inc.) and they can not or will not provide any specifications. APC is very proprietary about any thing they make.

I did locate a schematic for a UPS not necessarily this one as I have no idea what it came out of but it was in Russian. However the electrical symbols were for the most part identifiable. The transformer in the schematic was an iron core with three separate windings.

I read the link you posted (thank you) but from what I can gather it does not appear to be and auto-transformer.

From your dimensions and wire gauges it sounds like the transformer is actually around (say) 200VA only (although your weight of 15 pounds sound quite high) giving a current of around 12.5A (which matches the 15A fuse you mention).

That gives you a start. You could either test the transformer under decreasing resistive load and watch what happens to the transformer voltage (as the resistance decreases and the current increases and the transformer output voltage will drop) or alternatively (based on the 15A fuse) you could just use the transformer below 15A.

One thing to be aware of is that operating the transformer at or near the rating of the 15A fuse for extended periods of time may be enough to overheat the transformer and operate its internal thermal fuse. For example, the UPS manufacturer may have used a 15A fuse instead of a 10A fuse to prevent false tripping but the transformer is not rated for 15A continuously (perhaps say 12A).

It is generally best to de-rate the output current if you are going to use an unknown transformer like this in a power supply (at least for extended periods of use).

Don't get too exited. I've seen this size of transformer on "950VA" UPS. You'll laugh more if you see the size of the power mosfet heat sink. Of course these sizes will not handle that high power for long. But cheap UPS manufacturers rely on the fact that the small ~7Ah lead battery they use, won't provide power long enough to fry them. Still, at the end of battery discharge after some time offline, the case is hot enough to fully cook a couple of eggs. Conclusion: Don't expect more than ~7A continuous output from this transformer, and this providing enough space. S.M.

The specs that you mentioned are, probably, specs of the UPS...and not the transformer's.

It may well be as advertised.

I would guess the main winding is the BK-Wh. It should have the highest resistance. Ther should be infinite resistance to all other windings. The Y-Blu winding will be a small buck or boost winding that can trim about 2 volts on the output.

A 15 amp fuse on the primary will give about 1800VA, so an output of 50 amps is possible.

We do not know the duty cycle of this transformer, but class H is about 140C internal temperature. Don't let the external temp go above about 70C. (Too hot to touch).

So, fire up the BK, W leads, and start loading the secondary. Start with about 2 ohms, 150 watt rated load. That will give you about 8 amps. Watch the temperature over an hour. If it starts to smoke, shut it down. Progressively add more load and monitor.

This is where the back yard tinker shows his mettle.

From the description of the wiring connections you have provided, I suspect the transformer has been designed to accommodate variation in input voltage. Your primary input coil would be the black/white coil. With an output of 14.4V from the output coil, you have a ratio of 8.33, more or less. When you apply approximately 105 Volts to the two input coils connected in series (vellow/black 105 V, Blue/black joined), you should have approximately 14.35 Volts output. If you reverse the second coil (Input on white/blue, Yellow/black connected) and apply 135 Volts, you should have an output of 14.5 Volts. This transformer appears to have been designed to provide a relatively constant output over an input range of 105 to 135 volts.

Were it earlier in the evening and were I to have more energy available, I would calculate the actual turns ratios of the three coils, but I am too tired to address that tonight...

Thank you all for taking the time to assist me.

Perhaps a bit more of an explanation as to what I am trying to accomplish would be helpful.

I live full time in an RV most times off the grid and right now my only source of electricity is a generator.

The RV has a converter which makes a stable 12 power supply but is a lousy charger. The heart of the converter is a ferroresonant transformer. I will admit that I do not understand all the theory of operation for this type of transformer but in practice I can tell you it never attains an adequate voltage to charge a lead acid battery.

At first I thought that perhaps the transformer could be modified to produce a couple of extra volts but then my knowledge of transformers didn't support such a move.

My objective is to be able to charge my batteries in a reasonable amount of time so that the generator can be shut off.

If I can get the voltage from the converter up I have a wide range of voltages I can use because the output will feed into a Xantrex C 60 controller. It can accept voltages up to 55 volts at 60 amps and then deliver a very precisely controlled three stage charging circuit.

I then though of just replacing the ferroresonant Transformer with a straight up step down transformer some where in the vicinity of 16volts. Sounds simple but I have had no luck locating such a transformer. That is when I happened upon the transformer described in previous post and suspected of having come out of a UPS. The person I got it from swears up and down that it will deliver 16. 4 volts at 50 amps by connecting the yellow and white wires to my 120 volt source and the connecting the black and white wires together.

So what do you all think?

Is there a way to dig out of this hole?

Forgetting all the theory for a moment and lets say I move on to the "smoke test" what is the proper way to load the UPS transformer for testing.

I have a carbon pile, a set of low ohms high wattage resistors, a DMM and a digital thermometer.

please give us a list of your resistors.

I had a similar battery charger transformer, and was really puzzled by the tank circuit (the third coil and C-1 in your schematic), actually inquiring here on the forum as to its purpose. Several ideas came up, but finally, I opened the circuit by disconnecting C-1, and found that the output voltage dropped significantly.

So, check C-1- is it in spec? You might want to test the other capacitors as well- they appear to be filters that will give you constant output voltage.

There seems to be something wrong with your schematic- your output should come from the rectifiers- and I suspect this is set up more as a constant voltage power supply than as a battery charger. Most battery chargers I have worked with use a half-bridge rectifier which actually results in an output that is not constant, but winds up giving you 120 Hz ripple with peaks exceeding the nominal battery voltage. A constant-voltage power supply doesn't make a very good battery charger...

What is the open circuit voltage from your transformer? What batteries are you trying to charge?

That's a Parallax Power Supply for RVs.

The schematic shows only the converter circuit...maybe you should check

the charging circuit first before modifying the unit.

Tell us what type and size of battery you want to charge as 50 amps may be a touch too much!!!!

Charge/10 for example would imply a 500 Amp/Hrs battery, too big too lift!!!

So far you have tried in elaborating ur issues. My little contribution is to forget about the colour codes of the wires if you can't fine them and take the following lessons. 1) open all the secondary wises of the transformer. 2) Check the resistance of the continous wires Note two set wires of will be seperatly continous. 3) join the last and first wires of the two seperate continous wired. 4) Note the resistance. Note the higher the resistance, the higher the voltage, Since. V = I x R cos& Therefore V ~ R In efect the highest resistance is 16 and above volts. The two separate wired as in two are for 14 and 12 volts either way. Take care. )

CW

In answer to your question the resistors I have on hand are as follows.

10 different fixed power resistors with a 5 watt rating

820, 100, 50, 27, 10, 5, 2, 1, .5, .1 ohms

I also have a 200 ohm rheostat rated at 50 watts

One other item I have that I failed to mention in my last post that might be useful is an AC inductive amp meter

cwarner7_11

You are absolutely right the converter was designed to function in parallel with the coach batteries as a stable clean power supply.

That is the main function of the ferroresonant transformer AKA constant voltage transformer. It is capable of taking an input voltage variance of 5 to 10 percent and output a constant voltage. The capacitor you made reference to is used as an LC (inductor-capacitor) circuit ("tank circuit") tuned to the AC frequency to effectively filter out many of the distortions. The fact that the converter has a full wave rectifier bridge can't hurt.

http://www.ustpower.com/Support/Voltage_Regulator_Comparison/Ferroresonant_Transformer_CVT.aspx

Now in my particular situation it makes a lousy charger never attaining the voltage necessary to properly charge a lead acid battery. So my first thought was that perhaps I could modify the transformer. Maybe wire the two secondary winding in series to attain a higher voltage output. I can work with a wide range of output voltages (16 to 55 volts) because the DC output will be further conditioned by a charge controller. However if it can be modified it is beyond my expertise. That is the reason I purchased the transformer that I suspect is from a UPS. The question is will the UPS transformer function as a step down power transformer.

Andy Germany

Coach Batteries

4 - 6 volt deep cycle lead acid batteries

C20 Amp Hour rating for each battery 232

Configuration series parallel (6+6=12) + (6+6=12)

Total 12 volts at 464 amp hours

Recommended charge current is ~5%-13% of battery capacity:

Charging current 23 to 30 amps

So perhaps 50 amps is more than is actually required but I was going on the output of the original converter. When I am hooked up to a 120 volts source this charger I am attempting to make will also function as a power source. The output of the charger is further conditioned by a charge controller so there is little chance of overcharging the batteries. All 12 volt power in the coach is taken from the batteries. Should the voltage drop below the set charging voltage the charge controller would begin to supply current, up to its limit. At least this is my theory. Maybe 50 amps is too much I really don't know because I have never attempted to calculate the total current usage of the coach.

Dickson

The transformer resistance values are as follows:

The heavy (secondary?) black and white wires 0 ohms

Primary windings?

120 volts to the yellow and white leads

blue and black tied together open circuit voltage 16.4 volts

The resistance of these winding is .7 ohms

-------------------------------------------------------------------------

120 volts to the white and black leads

blue and yellow wires left open - open circuit voltage 14.4 volts

The resistance of these winding is .6 ohms

-------------------------------------------------------------------------

120 volts to the blue and white leads

black and yellow tied together open circuit voltage 12.9 volts

The resistance of these winding is .6 ohms

Is this consistent with what you were trying to explain.

Once again thank you all for your assistance. Seems to me that things are beginning to narrow down to will the (UPS) transformer work or should I keep looking. The unknown is how a UPS transformer works, which would be purely for my edification or much more importantly will it work. Since I have not been able to obtain any specifications as to its actual output the question remains how much current can the transformer deliver.

It would be nice to test it prior to actually committing myself. Can anyone explain, given the test equipment list in the prior post how I can bench test this unit?

Of course I would entertain any other ideas as to how to get out of this tunnel but for now this is all I can think of.

The resistors you have provide nowhere the watts required for a test.

Having said that, you do have some big batteries.

Get yourself a cheap automotive ammeter that can handle 50 to 60 amps.

Buy a 50amp full wave diode bridge and stick it on a good heat sink. You will dissipate about 100 watts in the diodes, and you don't want them hotter than you can touch.

Connect up your transformer with the lowest output voltage, through the diode bridge and your new ammeter to the batteries. For testing your batteries can absorb whatever you throw at them for a short time. (No pun intended). Depending on the amps you get, start reconnecting for higher volts.

Crydom M5060SB600 would work OK. About $45 CDN. You also need a big aluminum finned heat sink (weighing about a pound) to get rid of the heat. You can also use a smaller heat sink with a CPU fan force cooling, but that has more parts to fail. The ammeter should cost about $20. Use at least #10 wire for testing.

Not for the faint of heart. Keep a fire extinguisher handy. Do not do indoors!

Factual and funny.

Many thanks!

They are BIG batteries........

May I suggest a PWM charger with careful voltage control to make sure that the batteries are not overcharged......

In the interests in economy, you could use a lower charging rate to allow cheaper components to be used....charging will take longer of course.

GW

The resistors are used for rating solar panels, somewhere around 80 watts so I would have to agree with you.

Those are some good suggestion but in the interest of using what I've got what do you think of this.

I have a carbon pile originally designed to test batteries. It can absorb 500 amps for a short period of time. Without rectifying the output at all if I put the carbon pile across the output and my AC inductive amp meter in line do you think I could rate the transformer this way? I would keep increasing the load and measuring the amperage until the voltage dropped to an unusable level, of course keeping an eye on the temperature and or the presents of smoke. How hot can a transformer like this run continuously and safely? Got any ideas? If this or something similar would work I could bench test the transformer without disabling the converter and if it's not up to what the seller claims return it.

Andy Germany

The controller I made mention of in previous post is in fact a Xantrex C-60 a PWM controller designed primarily for solar installations but will work fine for this application.

I am planning on installing some solar panels a bit later but for now I am living on a generator and some batteries. It is important (fuel $$ wear and tear on the generator) to get the batteries up to charge as quickly and as is safely possible. I seldom discharge the batteries below 50% and the maximum charge rate for this set is around 30 amps so I may de-rate my plans a little.

So here is where I'm at.

No one has bit on the hook for modifying the existing ferroresonant transformer. I really did not think that was possible but then it was not so many years ago I would have thought a cell phone impossible.

I am going to proceed with an attempt at testing the (UPS) transformer. I could use any suggestion in that regard. If I get some reasonable results I will disassemble the converter and do a transformer transplant. Once install and I know I maybe getting way ahead of myself I can monitor the output. The controller has a built in amp and voltage gauge. In a good but not perfect world the converter with its new lease on life would charge my batteries by running the generator a couple of hours morning and night.

If none of the above works I guess I will be back looking for another transformer. Does anyone know of a source? I have looked but without any results.

Well, If your tr-er capable to provide 50A at 16V (800VA) it should be rather heavy one

may be more than 6kG-8kG. And wires of secondary for up to 50A may have at least 2.0-3.0 mm in diameter. If so it is a good tr-er and you have to get rid of doubts. Best regards.

Update

The continuing saga of the (UPS) transformer

OK

To answer your question the transformer weighs about 12 pounds (5.5kg) on a bathroom scale. Not a very accurate scale especially at lower weights but it's all I've got here.

The secondary windings have a 10 gauge (2.58826 mm) pigtail but the actual windings are much heavier.

Today I decided to put the transformer to the test. I wired it for the 16.4 volts output and 120 volts input. Plugged it in and it was right on the number +- a bit because I'm working in the field off a generator.

Then for the real test, how much current can this transformer produce?

I place a carbon pile across the secondary windings and slowly, every so slowly decreased the resistance. I had an inductive AC amp gauge around one of the output wires. I wish I new the resistance when things started to kick in but the carbon pile, or at least this carbon pile is not a precision instrument. The resistance seems to vary 20 or so ohms by just looking at it. Also knowing the resistance and the voltage would have given me some sort of a check but that was not to be. Any way I kept loading it down and as I approached the 50 amp mark my generator would flair and the Transformer's output put would jump to 75 amps at 13.5 volts, can't hold it there very long as the carbon pile begins to heat up. No smoke and the transformer never even got warm to the touch. The carbon pile sure did though.

So this surplus (UPS) transformer looks as though it may very well meet my needs.

Tomorrow I will do the converter transplant and I will let you all know how it performs in the circuit with a set of batteries.

Nothing else to report tonight except this is the first time I ever put AC voltage over a carbon pile. Even though it was only 16 or so volts it put on quite a show. Sparks jumping up and down the side of the carbon made it look like a Frankenstein experiment.

Hopefully tomorrow I can proclaim, "It's alive"

Did you ever find out about this transformer? I know it is used in APC UPSs. I need more info as well.

I recently pulled 2 of these transformers out of a smoked APC Smart UPS 3000 circa 1997.

Initially I had hoped to use this unit, but upon power up a single 200v 40amp MOSFET (RFP40N10-H7 obsolete) blew on the board. This unit has 4 banks of 8 (yup... 32 MOSFETS) of these.

Well... I only had a dozen or so 200v 36amp 0.04 ohm (IRL540N) replacement on hand. Very close characteristics, but what the heck the house only burns down once right?

Well, I was concerned as to why the first MOSFET smoked (mildly really), checked nearby 20ohm 1/8th watt resistor. It was fine & damage to board was relatively minor. Just another popped FET. Replaced many. Whatever. Anyway, when I replaced it? The unit appeared to run fine for bout 15-20mins & then slight odor & then traditional pop & breaker trip & yes flames until I disconnected 48v battery. This time the whole single bank of 8 MOSFETS cascade failed. All other FETS fine. So I decided it had more value in parts to me that replacing obsolete FETS with close substitute. Too sketchy with demonstrated unpredictable / unreliable results. The unscathed remain g 24 obsolete MOSFETS, Transformers & Low ESR caps & remaining discretes have greater value than troubled UPS. Parts now.

So the transformer....

Using my old Fluke 77 & variac, I conclusively determined this is NOT AN AUTOTRANSFORMER. There is isolation between the 2 primary windings (BLK/WHT) & (BLU/YEL) & 1 secondary windings (BLK/WHT).

I suspected the actual REAL primary is the BLK/WHT pair as there is a 20amp cartridge fuse in series with the 4pin Molex connector.

Here are the characteristics:

PRIMARY (16ga. BLK/WHT) = .5ohm

PRIMARY II (16ga BLU/YEL) = .3ohm

SECONDARY = (10ga BLK/WHT) = .2ohm

124.5VAC applied to 16ga BLK/WHT yielded 14.5VAC 10ga SECONDARY

The 16ga. BLU/YEL. followed the REAL primary applied voltage. So if I rolled up the variac to 50VAC on the REAL (BLK/WHT) primary? I observed 50VAC on the 16ga. BLU/YEL pair.

Conclusions? Well, I'm guessing the application in the UPS is to use the BLU/YEL pair to monitor the OUTBOUND AC voltage to control the flyback circuit.

Indeed this is a great 14.5VAC step down transformer, but in the DC-AC inverter application, the 10ga. BLK/WHT is actually the primary. I am convinced & I plan on using these transformers for half wave, unregulated, dirty pulsed DC lead acid battery charger with a ballast resistor to limit charge current.

Dirty old buzz box, with single 100amp diode, bad to the bone battery boiler LoL.

Why 1/2 wave? Well, why don't you ask lead acid chemistry. They seem to charge better with dirty pulsed DC. Don't ask me why. I've gotten better results than full-wave bridge rectified & filtered DC.

Side note: I've been doin this stuff since 1970. Laminated plate core transformers are slowly going away w/ switch mode power supply's (using ferro-resonant, powdered iron core flyback transformers) in everything.

These are a rare find. I save bout every transformer I get my hands on. They're durable & versatile and require little concentric componentry. Down n dirty EMP resistant power supply. Not so much with the switch mode crap. And remember... the municipal power is noisy, and dirty as Flint water. You wonder why power supplies are the highest failure item in electronics? And I won't get into all the crap Chinese capacitors I replace very often in these switch mode power supplies.

Anyway, I don't need intelligent charger to charge deep cycle (Non-AGM) old school lead acid batterys. Just an quality Amp meter, quality Volt meter, ballast resistor selection (golf cart wire wounds are nice, often mounted on bakelite term board, incandescent head lights will work too or you can wind yer own with 12-2 or 14-2 stripped & strapped to terminal strip) & quality hydrometer.

Hope this helps. Enjoy & keep your transformer. You'll regret you scrapped it for copper.