TransistorIRF630
Max junktion temperature=175 C, radi sigurnsti uzimamo 150 C
Ambient air temperature=80°C
Rth j-c = (175°C - 80 °C) /60W = 1.583°C/W.
Rth j-c = (150°C - 80 °C) /60W = 1.666°C/W.
Max. case temperature when dissipating 60W = 175 − (60 x 1.583) = 80°C (approx).
Max. case temperature when dissipating 60W = 150 − (60 x 1.666) = 55°C. (approx).
Thermal resistance Rth c-hs between case and heat-sink = 2°C/W.
Max. heat-sink temperature when dissipating 60 W = 80 - (60W x 2) = 80-120 = -40°C.
Max. heat-sink temperature wnen dissipating 60 W = 55 - (60W x 2) = 55-120 = -65°C.
To reach ambient air temperature = 80°C Thermal resistance of heat-sink must be better than:
(-40°C - 80 °C)/60W =-120°C /60°C = -2°C/W
(-65°C - 80 °C)/60W =-145°C /60°C = -2.41°C/W
Shto bi znacilo da bi tranzistpor imao disipaciju 60 W potrebno je vrsiti hladjenje putem pumpe odnosno frizidera, shto ne znaci da se ne moze koristiti na manju disipaciju normalno uz adekvatan hladnjak.
macedo