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Q2a)i) Thyristor Heat sink • T, Τς Heat flow (5 Marks) Q2a)ii) Rys (Thermal resistance, junction to heat sink) T, (Junction temperature) o Is Heat sink temperature RSA Мер (Thermal capacitance) (Thermal resistance, heatsink to ambient) TA (Ambient temperature) T.= Heat sink temperature (°C) R = Thermal resistance (due to conduction) between the thyristor junction and heat sink (°C W.1) T= Ambient temperature of the cooling medium (°C) Rs - Thermal resistance between the heat sink and the ambient surroundings M=Heat sink mass (kg) Cp = Specific heat capacity of the heat sink [ (kg °C) (5 Marks) Q2b)) Thyristor mean current=1/3 = 660/3 = 220A Average power dissipation in thyristor,