What are the details for the heat dissipation for the Preventa XPSAC and XPSECME safety modules?
Criterion for relay contacts to be worn out electrically is contact resistance is >= 100 mOhm.
Given two contacts with 100 mOhm each in line and the thermal sum current of 10,5 A distributed over 3 channels in case of XPSAC gives a maximum heat dissipation of 7,35 W in the output channels of the XPSAC.
Given two contacts with 100 mOhm each in line and the thermal sum current of 12 A distributed over 6 channels in case of XPSECME gives a maximum heat dissipation 4,8 W in the output channels of the XPSECME.
Initial contact resistance is below 15 mOhms, which results in much lower dissipation of 1,1 W resp. 0,7 W (values for the circuit breakers were given for new contacts).
Thus the actual dissipation depends on load and wear conditions of the contacts.
Another important factor for heating of the relays is arcing and, in case of arcing, switching frequency.
Given calculation is valid for use that can be assumed static and no arcing.
The dissipation in the outputs add to the power consumption of the module given in the data sheet.