[Amps] Transformer ?

[Paul Kraemer]

Question for the commercial power utilities guys:
Is there an advantage to delta / delta or delta / wye isolation transformer 
for 480 vac 3ph to 240 vac 3ph?
The load is scr controlled resistance heat apparatus and voltage is fixed at 
240 vac 3 ph
When the load was dc drives it seemed that drive always wanted a wye source 
from the transformer?
Shopping internet for a rather large isolation transformer and am concerned 
about making the best choice
Any 150kva units out there in your surplus?
Thanks for any help and opinions
Paul K0UYA