200A on-off switch

[ReefGuru]

Ichan did a good job providing more detail about what I was saying.

So you "prefer using a direct current breaking method" - clearly it's not your money because we are talking about less than $5 in what we proposed versus the sticker shock you will get by using a solenoid. Clearly, just as it took a few posts to tell us that it was 150 amps,you are not telling us everything. Vehicles require a mechanical disconnect, but that was not framed in the problem either. Big secret.

"I will design the switch circuit" - you're not designing anything, just bolting in an expensive,unreliable, solution that will lose a fair bit of power in the switch contacts at those currents.

Yes...do the math: contact resistance times 22,500.

Anyway, spend the money and proceed with bolting in the 100 year old tech "circuit design". And don't get too surprised when you are dissipating a couple dozen watts from the switch contacts.

You should also thank people that were helpful and who took their time to respond to help you out, not just vote up your favorites by pushing the button.

I still love you, if you are worried about what I wrote here 

 

In my travels through industrial locomotion (underground coal mining, conveyor systems, etc) there is no such thing as solid state current control... just about everything uses high current contactors. Need more current.. add more poles. Expensive? Yes, but far from unreliable in my experience. In my (worthless) opinion, i would assume an off the shelf contactor will be much less trouble and far more reliable than a homebrew high current solid state switch.

[max]

You can try following circuit, use transistors with lowest Rds 1 or 2 mohm.

[solutions]

In my travels through industrial locomotion (underground coal mining, conveyor systems, etc) there is no such thing as solid state current control...

Sorry grampa, you may be using those on your century old coal wagons, but....

Motor controls these days use PWM switching with MOSFETS or IGBTs. the 'switches" are already there in the system.

Ground the gates on N devices and no current flows. Take the speed "rheostat" to zero speed by grounding it and no current flows.

Contactors are made to break a DC arc at very high current without welding the contacts. NOT NECESSARY.

If you are doing something to hack the circuit so no current flows, that is "current control". And you can do that with a frickin DIP switch, the currents are so low (if you pick the right place in the system to do it). No arcs, no contacts to weld or get hot

[Gallymimu]

IGBT would be an easy solution. 

This one is a personal favorite at 700A: http://www.microsemi.com/existing-parts/parts/61264?catid=1248

That said a straight MOSFET with very low RdsON might be better for power dissipation.

[zac]

If you just need to switch the power on and off, a latching relay is a possibility.  Unlike a conventional relay, they require no power to maintain state, only to switch.  I have purchased some surplus high current (50A and 100A) units from ebay inexpensively.  Some 100A and 200A versions are also used in utility smartmeters (with remote disconnection capability) so those may be available at a reasonable cost.