Hey r/electrical, I'm having some trouble with a couple of transformers I got for free.

My problem is that no matter how I connect them to 120V AC 60Hz, they act as shorts and trip the breaker/kill the lights on the same household leg. I have tried connecting them directly to AC, connecting them in series with a power resistor to limit current to 4A, and connecting them with a "soft start" setup (A dual throw relay that starts the transformer connected in series with a hair dryer drawing 13A for a couple seconds, then switches the relay to short the hair dryer and connect 120V solely to the transformer for 150ms only to avoid tripping the breaker). No matter what, the transformer reads ~3-4V on the secondary at its max.

I do not know what their current rating is, however they were pulled from an 8kW, 240V UPS, and have 10AWG conductors on both the primary and secondary, so I'm just blindly assuming they each have a rating around 3 or 4kVA. I unfortunately didn't take a picture of the configuration they were in inside of the UPS. The only detail I can give is that they were joined together by one high side conductor. I'm thinking this might mean they were manufactured to be 120V transformers, and together form a 240V transformer. Although I do not know if they are step-up or down, though probably down.

They are likely Emerson transformers, going by the labels on other components in the UPS. I couldn't find any results for datasheets or manufacture pages, but they have the following information printed on them: (1st transformer - Top side: PL-2 , 02-769372-00-2; Left side: MRP366510; Right side: 021795-6; 2nd transformer - Top side: PL-2 , 02-769372-00-2; Left side: MRP252062; Right side: 021595-57; as well as some various pass marks like excitation, hi-potential, EIC, and IER). I don't know by what method the UPS failed (one of the large inductors elsewhere in the system had melted insulation), but I'm working under the assumption that these transformers work fine. If I measure their resistance, both the high and low are very low, and show as ~0 Ohms. However using a simple LCR meter from China, they have a 0.5mH inductance across the high side, and 2.2mH inductance across the low side. (I only know which one is high and low because there are tags on the conductors denoting H and X). If I measure the inductance between either low side conductor and the CT conductor, I get 0.5mH.

Each unit weighs about 2kg, and is 8.5x10x8cm, so they're definitely hefty but not super large or heavy. Pictures

Any help would be greatly appreciated. Is there a chance the transformers are dead and are actually shorted? Maybe it overheated and some windings fused. Would I still see an inductance in the mH? Is it the inrush current? That is why I tried the hair dryer soft start. I don't have any NTCs rated high enough for this, and I don't want to pay $11 for one from my electronics store if it probably won't work. Could the transformers be rated for a lower voltage?

Cheers in advance!