Solid-State Switching Devices for Resistive Loads Solid-State Relays 3RF22 solid-state relays, three-phase, 45 mm Dependence of the device current I e on the ambient temperature T a and the heat sink resistance R thha (three-phase controlled) 160 Module power loss in W 140 NSB0_01673 e in A M 120 Rthha 100 0,26 K/W 0,33 K/W 80 0,62 K/W 0,44 K/W 60 0,9 K/W 1,3 K/W 1,7 K/W 2,2 K/W 40 3 K/W 4 K/W 20 7 K/W 5 K/W 0 10 K/W 4 12 20 28 30 36 Ambient temperature in °C Device current in A a e 0 10 20 30 40 50 60 Type current 30 A (3RF22 30-.AC..) 250 Module power loss in W NSB0_01674 e in A M 200 Rthha 150 0,06 K/W 0,09 K/W 0,25 K/W 0,15 K/W 100 0,4 K/W 0,6 K/W 0,8 K/W 1,1 K/W 50 1,5 K/W 2 K/W 3 K/W 0 6 K/W 4 K/W 5 15 25 35 45 55 Ambient temperature in °C Device current in A a e 0 10 20 30 40 50 60 Type current 55 A (3RF22 55-.AC..) Arrangement example Given conditions:
I e = 55 A and T a = 40 C. The task is to find the thermal resistance R thha and the heat sink overtemperature dT ha . This results in: dT ha = R thha Ч PM = 0.09 K/W Ч 227 W = 20.4 K. From the diagram on the left → P M = 227 W, from the diagram on the right → R thha = 0.09 K/W. At dT ha = 20.4 K the heat sink must therefore have an R thha = 0.09 K/W. 23 Siemens · 2009