| We recently acquired a machine that requires a 575 volt supply for three | large 3 phase AC motors. Combined the motors draw about 340 FLA. We were | told the machine was 480 volt, so when the thing came in we were rather | surprised to find it wasn't. Now I need to find a transformer solution | ASAP, unfortunately I've been quoted long lead times. Can anybody recommend | suppliers who might have such a transformer "on the shelf"? Seems like I | would need at least a 250Kva 480v-575v transformer, or a boost arrangement | to achieve the same thing. This machine needs to be operational as quickly | as possible and I don't have 4-5 weeks to wait for delivery.
Motors are usually quoted as being for voltages like 115, 230, 460, and 575. But the nominal voltages are 120, 240, 480, and 600. Had you gotten the correct voltage, it would have been labeled as for 460 and you would run it on 480. If you were in Canada, you get the 575 version and run it on 600 which is commonly available in Canada.
So ultimately what you need is 600 volts.
Does the machine require WYE (needs the neutral) or will it work on DELTA?
There are several options.
A 480 -> 240x120 single phase transformer probably could be wired up as a boost transformer. The secondary would be wired for 120 by paralleling the two secondary windings. Then that winding would be put in series with the primary.
Draw an equilateral triangle on a piece of paper. Now draw extensions on each of the 3 lines in the clockwise direction with a length of 25% more. The ends of those extensions will be the boosted delta.
I don't know the ratings you'd need. I've never done the capacity calculations for buck-boost transformers.
If your power is coming in the form of 480Y/277, you could also boost the 277 to 346 to get 600Y/346. Transformers are not made for these voltage combinations, but you could use the 480 -> 120 for this in a derated form to make 277 -> 69, and turn that into a 277 -> 346 boost. This would simply extend the WYE hot legs.
You could build a delta-delta isolation transformer bank using *SIX* single phase 600 -> 240x120 transformers running backwards. Wire the transformers for 600 -> 240 (secondary in series). Now I will refer to it as a 240 -> 600 volt transformer. Take TWO of them and wire the 240 volt primaries in series and the 600 volt secondaries in parallel. Now two of them make a 480 -> 600 volt transformer set. Three such sets lets you make a closed delta. I'm guessing this can be done with 50 kVA transformers (about 00 at full list price, which should be half that if you shop around, and maybe even less if you find someone who likes the idea of selling six of them at once).
Since you need them fast, call Canadian suppliers as these would generally only be a stock item in 600 volt land (600 volts is rare in US).
Are you going to get the vender of the machine that flubbed the order to spring for the cost of these transformers?
Be sure a competent electrician wires these, and properly tests the voltages before closing the delta.