Check the datasheet.
Most TO-3's are in the 50 to 150W range.
The specification states that the case is kept at room temperature (25øC), which realistically means either very short duration use (essentially pulsed) or water cooling. A large heatsink with a few hundred watts might hold 25 above 25øC (or 40 in Australia
), or 50-65øC absolute.
If there isn't a graph of it, there's a derating spec which usually goes from say, 150W at 25 down to 0W at 175øC, so say 75W at 100øC. With good thermal contact you can assume the case is the same temp as the heatsink (plus a few degrees, you should be able to find some specs for conductivity of insulators and stuff).
Tim
Most TO-3's are in the 50 to 150W range.
The specification states that the case is kept at room temperature (25øC), which realistically means either very short duration use (essentially pulsed) or water cooling. A large heatsink with a few hundred watts might hold 25 above 25øC (or 40 in Australia
), or 50-65øC absolute.If there isn't a graph of it, there's a derating spec which usually goes from say, 150W at 25 down to 0W at 175øC, so say 75W at 100øC. With good thermal contact you can assume the case is the same temp as the heatsink (plus a few degrees, you should be able to find some specs for conductivity of insulators and stuff).
Tim
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