automation and drives sirius sc solid state switching devices sirius sc solid state switching...

Automation and Drives

SIRIUS SCSolid StateSwitching DevicesSIRIUS SC

Solid State Switching Devices

How Do I Select the Right Heat Sink for my Solid State Relay?


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 RthHS

1

2

3

4

Theoretical ApproachTheoretical 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 Ploss and the permissible thermal resistance RthHS on the basis of the diagram contained in the solid state relay‘s data sheet.

Determination of the total power loss Ploss total and the permissible RthHS total for cases where several relays are applied on a single heat sink.



SIRIUS SC

Actual RthHS

smaller than perm. RthHS

Heat sink selection

Determination of the actual RthHS

4

5

YES

4

NO

Completed

6


Heat sink selection from a heat sink manufacturer‘s data sheet on the basis of the total power loss and the permissible RthHS total.

Determination of the actual RthHS 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 RthHS 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.



SIRIUS SC

1

2

3

4

5

6

1 2 3 4 5 6

6 x 5 K/W 1 x 0.83 K/W


Capacity of heat sinks

The RthHS 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 RthHS value = inferior heat sink Small RthHS 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: Ploss = 14 W, RthHS = 5 K/W = 14 W x 5 K/W = 70 K.With 6 relays: = 70 K, Ploss total = 84 W RthHS = 70 K / 84 W = 0.83 K/W. Or more simple: RthHS divided by the number of relays = 5 K/W / 6 = 0.83 K/W.



SIRIUS SC

11stst Example Example

Starting conditions


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 sinksDepth: max. 80 mm = tall heat sinks

Width: any

On the basis of the given conditions, six 3RF2120-1AA02 items are selected.



SIRIUS SC



3

2 6 10 14 18 22Ie in A

1,0 K/W

1,3 K/W

1,7 K/W

2,4 K/W

3 K/W

4 K/W5 K/W6 K/W8 K/W10 K/W

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60Ta in °C

PM

in W

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 RthHS of 8.5 K/W per relay can be determined.

Ploss total: 6 x 8 = 48 W

RthHS total: 8.5 / 6 = 1.41 K/W



SIRIUS SC

Heat sink selection


4

5

6


Heat sink selected from www.alutronic.de: PR131/100/SE (100x100x50)at Ploss = 40 W RthHS of 1.49 K/W

Based on the diagram contained on the heat sink‘s data sheet, a of 70 K can be determined at Ploss = 48 W. This results in:RthHS = 70 K / 48 W = 1.46 K/W



SIRIUS SC

Actual RthHS


4

NO6

Heat sink selection

4

5


The actual RthHS of 1.46 K/W is higher than the permissible RthHS 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 Ploss = 40 W RthHS of 1.07 K/W



SIRIUS SC


Actual RthHS


5

YES

Completed

6


Based on the diagram contained on the heat sink‘s data sheet, a of 50 K can be determined at Ploss = 48 W. This results in: RthHS = 50 K / 48 W = 1.04 K/W

The actual RthHS of 1.04 K/W is smaller than the permissible RthHS of 1.41 K/W.

The heat sink is suitable !!As the actual RthHS 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.



SIRIUS SC

22ndnd Example Example

Starting conditions


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 sinksDepth max. 100 mm = tall heat sinks

Width min. 230 mm

On the basis of the given conditions, ten 3RF2120-1AA02 items are selected.



SIRIUS SC



3

2 6 10 14 18 22Ie in A

1,0 K/W

1,3 K/W

1,7 K/W

2,4 K/W

3 K/W

4 K/W5 K/W6 K/W8 K/W10 K/W

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60Ta in °C

PM

in W

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.


Ploss total : 10 x 16.5 = 165 W

RthHS total : 4.0 / 10 = 0.40 K/W



SIRIUS SC

Heat sink selection


4

5

6


Heat sink selected from www.alutronic.de: PR237/100/SE (100x250x83)at Ploss 160 W RthHS of 0.46 K/W

Based on the diagram contained on the heat sink‘s data sheet, a of 78 K can be determined at Ploss = 165 W. This results in: RthHS = 78 K / 165 W = 0.47 K/W



SIRIUS SC

Actual RthHS


4

NO6



2

3

The actual RthHS of 0.47 K/W is higher than the permissible RthHS 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 RthHS values.

On the basis of the given conditions, ten 3RF2130-1AA02 items are selected.



SIRIUS SC

6 10 14 18 22 26 30 34Ie in A

0,3 K/W

0,5 K/W

0,79 K/W

1,25 K/W

2 K/W

3 K/W4 K/W5 K/W7 K/W10 K/W

0

10

20

30

40

50

60

0 10 20 30 40 50 60Ta in °C

PM

in W



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.


Ploss total : 10 x 14 = 140 W

RthHS total : 5.0 / 10 = 0.50 K/W



SIRIUS SC

Heat sink selection


4

5

6


The same heat sink is once more selected from www.alutronic.de: PR237/100/SE (100x250x83)at Ploss 160 W RthHS of 0.46 K/W

Based on the diagram contained on the heat sink‘s data sheet, a of 68 K can be determined at Ploss = 140 W. This results in:RthHS = 68 K / 140 W = 0.485 K/W



SIRIUS SC

Actual RthHS


6


YES

Completed

The actual RthHS of 0.485 K/W is smaller than the permissible RthHS of 0.50 K/W.

The heat sink is suitable!!

Caution:Caution:It must be assured that the power loss emitted to the ambient 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 air by the heat sink in the form of heat is transported out of the control cabinet. Otherwise, the temperature within the control control cabinet. Otherwise, the temperature within the control cabinet would exceed the maximum value and the solid state cabinet would exceed the maximum value and the solid state switching devices would be destroyed.switching devices would be destroyed.

automation and drives sirius sc solid state switching devices sirius sc solid state switching...

Documents

example heat sink

suitable heat sink

w r thhs total

permissible r thhs total

right heat sink

bare heat sink

single heat sink

different heat sink