Anyone have any ideas what fan speed controller I need? I've used the cheap rheostat versions and they just can't supply the amperage. I bought a 5 amp variac and it blows the 5 amp fuse on startup. I tried a 6 amp fuse and half the time it will blow that. When it doesn't blow it and I dim the voltage do around 78 volts everything runs OK for a few minutes then the fan shuts down due to the thermal overload protection and takes about an hour to cool down before I can plug it back in and have it work again.... not sure what I should try next?