I was trying to compare the dissipation of an electromechanical relay with a MOSFET switch. I thought I knew how to do this but I don't believe my results.
Here is a data sheet for a relay: https://www.azettler.com/pdfs/az2850.pdf
This relay is rated for 30 or 40 amps. My load is 20 amps.
The data sheet says the contact resistance is "< 50 milliohms initially."
So 20 amps times 50 milliohms is 1 volt and 20 amps times 1 volt is 20 watts. And that's just one pole. I actually wanted to switch both poles. I can't really believe that a relay would be dissipating 40 watts!!! I can't really believe a 1 volt drop across a pair of relay contacts.
So, I thought, maybe they mean micro-ohms. But I looked up a P&B datasheet
https://www.te.com/commerce/Documen...&DocNm=1308242_T92&DocType=DS&DocLang=English
and they're saying 100 milliohms.
What am I missing here?
Here is a data sheet for a relay: https://www.azettler.com/pdfs/az2850.pdf
This relay is rated for 30 or 40 amps. My load is 20 amps.
The data sheet says the contact resistance is "< 50 milliohms initially."
So 20 amps times 50 milliohms is 1 volt and 20 amps times 1 volt is 20 watts. And that's just one pole. I actually wanted to switch both poles. I can't really believe that a relay would be dissipating 40 watts!!! I can't really believe a 1 volt drop across a pair of relay contacts.
So, I thought, maybe they mean micro-ohms. But I looked up a P&B datasheet
https://www.te.com/commerce/Documen...&DocNm=1308242_T92&DocType=DS&DocLang=English
and they're saying 100 milliohms.
What am I missing here?