As you approach the genhead's rating you have to consider thermal breakdown of the enamel insulation covering the windings which is affected by time and temperature. Not to mention the unknown quality of the enamel.
I'm reminded of Clint Eastwood in Dirty Harry:
Harry Callahan: I know what you're thinking. "Did he fire six shots or only five?" Well, to tell you the truth, in all this excitement I kind of lost track myself. But being as this is a .44 Magnum, the most powerful handgun in the world, and would blow your head clean off, you've got to ask yourself one question: Do I feel lucky? Well, do ya, punk?
Other folks have run these up to and past their nameplate limit and reported they don't even get warm. Certainly the ST-series blows an awful lot of air, but who knows what's happening deep down in the windings.
I wouldn't take an ST5 above 80% of its rating in continuous service. But that's just me.
Quinn
