1577

A power converter is started from cold and switched off after five minutes. The semiconductor devices in the power converter produce a total loss of 30W and are all mounted onto the same heatsink. The thermal resistance between the heatsink and ambient is 1.7°C/W and its thermal capacitance is 100J/°C. The ambient temperature is 40°C. Calculate the heatsink temperature at switch-off. (sketch thermal circuit) ANS: (48.7°C)