1. Automation and Drives SIRIUS SC Solid State Switching Devices SIRIUS SC Solid State Switching Devices How Do I Select the Right Heat Sink for my Solid State Relay?

2. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 2 SIRIUS SC Starting conditions Solid state relay selection Power loss and permissible R thHS 1 2 3 4 Theoretical Approach  Load current  Max. ambient temperature  Heat sink assembly conditions Selection of the solid state relay on the basis of the load current. Determination of the power loss P loss and the permissible thermal resistance R thHS on the basis of the diagram contained in the solid state relay‘s data sheet. Determination of the total power loss P loss total and the permissible R thHS total for cases where several relays are applied on a single heat sink.

3. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 3 SIRIUS SC Actual R thHS smaller than perm. R thHS Heat sink selection Determination of the actual R thHS 4 5 YES 4 NO Completed 6 Theoretical Approach Heat sink selection from a heat sink manufacturer‘s data sheet on the basis of the total power loss and the permissible R thHS total. Determination of the actual R thHS on the basis of the diagram contained in the heat sink‘s data sheet with a given power loss. Verification whether the heat sink‘s actual R thHS is smaller than the permissible thermal resistance. If this value is not smaller, continue with the selection to verify a different heat sink. If no suitable heat sink is available, continue with step to try a larger solid state relay. 2 The heat sink for this application has been correctly dimensioned.

4. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 4 SIRIUS SC 1 2 3 4 5 6 123456 6 x 5 K/W 1 x 0.83 K/W Theoretical Approach Capacity of heat sinks The R thHS value reflects the heat sink‘s capacity, i.e. the heat sink‘s Kelvin temperature increase per power loss in Watt. Example:One heat sink with 4 K/W increases its temperature by 80 K at 20 Watt. One heat sink with 1 K/W increases its temperature by 20 K at 20 Watt. High R thHS value= inferior heat sink Small R thHS value = superior heat sink Application of several solid state relays on one heat sink If, for example, six relays are to be mounted on one heat sink, a heat sink which provides the capacity of six small heat sinks is required. E.g.:Per relay: P loss = 14 W, R thHS = 5 K/W   = 14 W x 5 K/W = 70 K. With 6 relays:  = 70 K, P loss total = 84 W  R thHS = 70 K / 84 W = 0.83 K/W. Or more simple: R thHS divided by the number of relays = 5 K/W / 6 = 0.83 K/W.

5. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 5 SIRIUS SC 1 st Example Starting conditions Solid state relay selection 1 2 3  6 heating cartridges 230 V / 8 A each  24 V DC control voltage  Max. ambient temperature of 45°C  Space for heat sinks: Height: max. 120 mm = long heat sinks Depth: max. 80 mm = tall heat sinks Width: any On the basis of the given conditions, six 3RF2120-1AA02 items are selected.

6. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 6 SIRIUS SC 1 st Example Power loss and permissible R thHS 3 approx. 8,5 K/W 4 3RF2020-. On the basis of the diagram, a power loss of 8 W per solid state relay is determined at 8 A. With this power loss and a maximum ambient temperature of 45°C, a maximum thermal resistance R thHS of 8.5 K/W per relay can be determined. P loss total :6 x 8 = 48 W R thHS total : 8.5 / 6 = 1.41 K/W

7. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 7 SIRIUS SC Heat sink selection Determination of the actual R thHS 4 5 6 1 st Example Heat sink selected from www.alutronic.de: PR131/100/SE (100x100x50) at P loss = 40 W  R thHS of 1.49 K/Wwww.alutronic.de Based on the diagram contained on the heat sink‘s data sheet, a  of 70 K can be determined at P loss = 48 W. This results in: R thHS = 70 K / 48 W = 1.46 K/W

8. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 8 SIRIUS SC Actual R thHS smaller than perm. R thHS 4 NO 6 Heat sink selection 4 5 1 st Example The actual R thHS of 1.46 K/W is higher than the permissible R thHS of 1.41 K/W.  Heat sink not suitable!! Selection of new heat sink Heat sink selected from www.alutronic.de: PR211/100/SE (100x111.5x67.5 sw anodized) at P loss = 40 W  R thHS of 1.07 K/Wwww.alutronic.de

9. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 9 SIRIUS SC Determination of the actual R thHS Actual R thHS smaller than perm. R thHS 5 YES Completed 6 1 st Example Based on the diagram contained on the heat sink‘s data sheet, a  of 50 K can be determined at P loss = 48 W. This results in: R thHS = 50 K / 48 W = 1.04 K/W The actual R thHS of 1.04 K/W is smaller than the permissible R thHS of 1.41 K/W.  The heat sink is suitable !! As the actual R thHS is considerable smaller than the permissible value, the heat sink manufacturer can be consulted to determine whether he recommends a bare heat sink or whether a special length of 80 mm is also sufficient.

10. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 10 SIRIUS SC 2 nd Example Starting conditions Solid state relay selection 1 2 3  30 heating cartridges 230 V / 4.5 A each  3 heating cartridges each are switched via one solid state relay  Control voltage 24 V DC  Max. ambient temperature 40°C  Space for heat sinks: Height max. 120 mm = long heat sinks Depth max. 100 mm = tall heat sinks Width min. 230 mm On the basis of the given conditions, ten 3RF2120-1AA02 items are selected.

11. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 11 SIRIUS SC 2 nd Example Power loss and permissible R thHS 3 approx. 4,0 K/W 4 3RF2020-. On the basis of the diagram, a power loss of 16.5 W per solid state relay is determined at 13.5 A. With this power loss and a maximum ambient temperature of 40°C, a maximum thermal resistance R thHS of 4.0 K/W per relay can be determined. P loss total :10 x 16.5 = 165 W R thHS total : 4.0 / 10 = 0.40 K/W

12. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 12 SIRIUS SC Heat sink selection Determination of the actual R thHS 4 5 6 2 nd Example Heat sink selected from www.alutronic.de: PR237/100/SE (100x250x83) at P loss 160 W  R thHS of 0.46 K/Wwww.alutronic.de Based on the diagram contained on the heat sink‘s data sheet, a  of 78 K can be determined at P loss = 165 W. This results in: R thHS = 78 K / 165 W = 0.47 K/W

13. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 13 SIRIUS SC Actual R thHS smaller than perm. R thHS 4 NO 6 2 nd Example Solid state relay selection 2 3 The actual R thHS of 0.47 K/W is higher than the permissible R thHS of 0.40 K/W.  The heat sink is not suitable !! Selection of new heat sink? As a heat sink with an increased capacity cannot be applied due to spatial reasons, solid state relays with increased capacity should be selected as they can cope with poorer R thHS values. On the basis of the given conditions, ten 3RF2130-1AA02 items are selected.

14. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 14 SIRIUS SC 2 nd Example Power loss and permissible R thHS 3 approx. 5,0 K/W 4 3RF2030-. On the basis of the diagram, a power loss of 14 W per solid state relay is determined at 13.5 A. With this power loss and a maximum ambient temperature of 40°C, a maximum thermal resistance R thHS of 5.0 K/W per relay can be determined. P loss total :10 x 14 = 140 W R thHS total : 5.0 / 10 = 0.50 K/W

15. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 15 SIRIUS SC Heat sink selection Determination of the actual R thHS 4 5 6 2 nd Example The same heat sink is once more selected from www.alutronic.de: PR237/100/SE (100x250x83) at P loss 160 W  R thHS of 0.46 K/Wwww.alutronic.de Based on the diagram contained on the heat sink‘s data sheet, a  of 68 K can be determined at P loss = 140 W. This results in: R thHS = 68 K / 140 W = 0.485 K/W

16. Automation and Drives SIRIUS SC Solid State Switching Devices A&D CD CC PM4 14.05.04 16 SIRIUS SC Actual R thHS smaller than perm. R thHS 6 2 nd Example YES Completed The actual R thHS of 0.485 K/W is smaller than the permissible R thHS of 0.50 K/W.  The heat sink is suitable!! Caution: It must be assured that the power loss emitted to the ambient air by the heat sink in the form of heat is transported out of the control cabinet. Otherwise, the temperature within the control cabinet would exceed the maximum value and the solid state switching devices would be destroyed.