Torque remains the same since the flux strength is the same. Flux strength is determined by the V/Hz ratio and 400/50 is the same as 480/60. So if torque remains the same but speed drops by 20%, that's the only reason the power rating drops by 20%. For most machines, it's torque that we need, speed is secondary. It might still be important, yes, but if it were me, I'd try it. I've done this sort of thing dozens of times and generally speed is relatively easy to deal with.Cooling would be an issue
current remains ~ the same v goes down 16%, power down about 20%
but torque should remain ~ the same???
assume 100 hp at 1760 rpm T = 300 lb ft
if we drop power to 80 hp and speed to 1470 so T = 285 lb ft, 5% less
makes sense since T ~ i ~ field strength
an issue may be controls
400/4 = 100 vac, marginal
AFAIK, when your speed changes in a fan/pump, the afffinity laws are:More like 40%.