Welcome to ECN.
I have a few questions regarding the UPS:
it needed a 480 volt 3 wire input
Is this 3 Wire Input 480 VAC 3 Phase 3 Wire, or 480 VAC 1 Phase 2 Wire + Equipment Grounding Conductor?
3 Phase 3 Wire Input would have 3 individual terminals on the Primary Side of the Transformer, most likely marked "H1", "H2" and "H3".
There would also be a Lug on the Enclosure, where the "EGC" (Equipment Grounding Conductor) would be terminated at.
1 Phase 2 Wire Input would have only 2 terminals on the Primary Side, and may be marked as "H1" and "H2".
The ECG would terminate to a Lug on the Enclosure, or possibly to a Lug on a Terminal Strip inside of a "Cabinet".
The EGC's Lug / Terminal would be Colored Green, or identified with a "Ground" symbol.
I WANT TO KNOW IF THERE IS A WAY TO CONFIGURE THE TRANSFORMER TO WORK WITH A SINGLE PHASE 240 VOLTS 3 WIRE INPUT AND STILL BE ABLE TO GET A 120/240 VOLT OUTPUT FROM THIS SYSTEM?
First off, _ONLY IF_ the Primary Windings are "Split Coil", and the Primary Side terminations have factory provisions, which allow the Primary Windings to be connected in either Series (480V), or Parallel (240V), the UPS may be used on a 240 VAC System.
If there is no "Input Voltage Changing Provisions" - such as reconfigurable jumpers, etc., then the UPS can only be used with a 480 VAC Input.
Secondly, you mention "A SINGLE PHASE 240 VOLTS 3 WIRE INPUT":
If by this you mean the input Circuitry has 2 Ungrounded Conductors + 1 Grounded "Neutral" Conductor, this may be an incorrect way to feed the UPS - especially if the Primary Windings are Isolated from the Secondary Windings.
If this Circuit is a 240 VAC Single Phase Circuit, the Primary side would only accept 2 Ungrounded Conductors.
If you mean the input is from a 240 VAC 3 Phase 3 Wire Circuit - such as from a 240 VAC 3 Phase 3 Wire Delta System, or a 240/120 VAC 3 Phase 4 Wire Delta System, or even a 208Y/120 VAC 3 Phase 4 Wire System, you have a 3 Phase Power System.
This would be a Circuit with 3 ungrounded Conductors, or a System with 3 "Active Circuit" Conductors having the same Voltage measured across them - as measured between "A-B", "B-C" and "A-C".
Another question regards the Secondary Side's Grounding Electrode System.
If this UPS _IS_ an Isolated Transformer type, the "Output" should be bonded to a Grounding Electrode System - actually the one used with the Utility Supplied Power System on-site.
Way too many questions / scenarios regarding this UPS setup - best if you contact the manufacturer for details.