I opened my APC 3000, it has two 1500 transformers in it. I expect it's much like the 1400.
Primary side has 4 wires: Black, blue, white, yellow. Secondary 2: white, black.
The primary side is all you need. APC uses it as an autotransformer. Measure the voltage on them, (or trace them if you can) Try to match them up to:
__150v
/
_120v
/
_90v
/
\
/
\
/_neutral
When the voltage goes low the AVR connects the output to 150v tap. Boosting the voltage back to 120. If the voltage is high, AVR connects the output to the 90v tap reducing the voltage to 120.
Since your voltage is always low. You can eliminate all of the circuitry. Unplug the connector and wire it up. You can parallel several of these transformers to meet your power demands. Leave the secondary UNCONNECTED. My transformers get warm, Measured 115'F, doing nothing. Not sure if under load they get hotter? May consider a fan.
I take it you have power to burn. The loss of 1kw in the wiring (30%) does not seem to bother you. On eBay a 3kw step-up to 220v transformer is <$100 with ship, By doubling the voltage, the power loss in the cable will be half... don't know if an extra 500 watts is useful. Depending on the step-up transformer, some can do 240v, If your 1750' cable has three wires, the lower losses by using 220v, that may be all you need. You have two 120 volt circuits, or 220 for what ever, with a neutral. Then you can sell off all your UPS.
Have fun.