I'm looking for a 17" rackmount transformer, around 15kVA. primary is 480VAC 3 phase, need either 240 single phase or just a step down to 208 3 phase wye.
Anyone give me some pointers to mfg that make these?
I do not think that it will be possible. Such a thing will be quite heavy - at least around 200 lbs (around 100 kg) for a 15 kVA unit. I know no rack hardware that can carry a weight like that. And very few people that would be able to handle the unit without a crane or similar aid. The dimensions are also getting tricky with smallest dimension in the foot range (around 250 mm).
Your best bet is to fit it onto a mounting plate at the base of the rack. It will surely contribute to a low center of gravity!
skogsgurra is correct. The form-factor of a 19" rack is horrible for transformers. The only option would probably be mounting the transformer in the bottom of the rack with augmented bracing.
We have used Tripplite box that had a large 10kVA 220 to 120 transformer, but haven't seen anything that takes in 480 in that configuration.
Sometimes what the customer wants.....he just can't have. Going to just suggest he puts in a PDU like everyone else and transforms from the 480 to 208.