Electronic heat sink HF92B series

In the above formula TJ stands for the junction temperature of the power parts of semiconductor(°C), TA stands for the ambient temperature (#C), P stands for general power consumption (W) and RJA stands for thermal résistance (°C/W) from junction to ambient. The thermal résistance of simplified SSR relays is made up of two parts as follow: RJA=RJC+RCA. In the formula, RJC stands for thermal résistance from junction to case and RCA stands for the thermal résistance from case to ambient For example, when we calculate the heat dissipation of KS15/D-24Z25, RJC of this relay is about 1.2°C/W, RCA is about 8.5°C/W. The max. allowable junction temperature is 12°C and the power consumption is P=U x I. When the current is 10A or below 10A, the TRIAC voltage drop is about 1.1V. The formula of product without heat sink is show as follow, 125- TA=1.1 XIX (1.2+8.5 According to the above formula, the max. current is 9.3A at 25°C ambient temperature and 6A at 60°Cambient temperature when the product dose not add a heat sink. If we add HF92B-120 heat sink to this relay and the reference thermal résistance is about 1.1°C/W. Neglecting the thermal resistance from SSR métal base to heat sink, and the voltage drop is about 1.25V on full load current. The formula will be 125-TA=1.5 X I X (1.2+1.1). Max. ambient temperature will be 40°Cwhen the operating current is 25A and the max. current will be 18A when the ambient temperature is 60°C. Due to the différent heat sink types, the corresponding thermal résistance changes. So there are différent current values under corresponding ambient temperature. - F