high power latching relay

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Well, if it is just a relay or contactor try to look for some with4 pole contacts rated @35 amps and use 3 of them in parallel and the 4th as a latch; better yet - use 2 relays to half the current and arcing etc. Money will get you into solid states but 4now use the "simple" approach
 

Use the mosfet as low side .... that is, load is above mosfet ... and mosfet source lead is at ground potential .....

Be sure to give the mosfets enough gate voltage, Vgs, so that they are fully turned on... If a mosfet is only partially turned on, it will have much greater 'ON' resistance, and much greater Vds across the part. Consequently, there will be much greater heat dissipation, and it will burn out.

... Still not completely informed as to all the aspects of your application, ... sounds good though.... Please report your results here ....
 
i must switch 100V DC (pulsated DC from a rectifier/transformer so it can go high as 170V peak) up to 100A) about 15 times per minutes (on/off cycle) , so that why i don't go with a relay anymore, they won't last more than 1 month!!

if i make two banks of 10 mosfet and put them back to back would it work correctly it would be better because of no polartity checking for the client (similar to a reverse battery protection)
of course i will use dc dc converter and opto coupler to be isolated from the 100vdc

would it be better to use mosfet drivers to turn on the mosfet?
 
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Do you just have only one polarity coming from your rectifier? Or do you actually have a set of positive DC pulses, and then a set of negative DC pulses, also?

The power Mosfets which you referenced are voltage controlled .... and should not require any significant current.... Just don't exceed the Vgs limit in the specification .... 30 Vdc
 
It might be that part of the main problem is to detect the instant of reverse polarity.... and to switch off the reverse current flow before it does any damage.
Could this be the reason why the relays that were used previously did not last too long?
 
Knowing now the frequency of switching, the only reliable solution for your application is in the solid state circuit. MOSFETs will do the job, you are on the right track..
 
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