I have a key switch which can handle 50v at 1A. I need to use it to switch 50v at 25 A. I understand that I can use a MOSFET to switch the higher amperage, but I understand they also burn voltage (voltage drop from source to drain).

Is there a more efficient method of switching the higher amperage? To my knowledge, there aren't any key switches which can switch this much power. I wasn't able to find a relay which can handle this much current either.

Thanks!

 

Use a contactor or selenoid?

 

Check out this one--it is rated at 100A, but costs $100

http://search.digikey.com/us/en/products/LEV100A4ANG/A101163-ND/2046688

 

From the details provided a contactor or solid state relay (SSR) will fit your needs.

 

I would just go to a junk yard and get a 12vdc selenoid off a ford starter.

 

I would just go to a junk yard and get a 12vdc selenoid off a ford starter.

Not if you were required to meet any standards or didn't want to hold any liability. Most automotive stuff like that is only rated to 32V max or less. That is not sufficient for 50V applications. Will it work.. Most likely.. Is it correct.. No

 

Also, a solenoid from a starter isn't rated for continous duty, and the OP hasn't given us that information yet.

 

If you are hot swapping a load I would stay away from relays or any other mechanical device as this will ruin the contacts. Select some high power FETS and place them in parallel if needed to get the required current.

 

depends on your application. A 'key' switch in industry means a 'safe' circuit, relay required, as solidstate switches are not considered 'safe'. Relays can and do switch heavy loads.