Night Train Posted January 12, 2011 Share Posted January 12, 2011 I am looking for ideas to make a really big DPDT change over switch, something that will be able to carry around 200A at 96V but it doesn't need to switch it, just carry it in each position. Something like this from a welder springs to mind. (random search image) Any thoughts as to either getting one or making one? What would be a good material to build it from? Cheers. Mods, Please delete if too OT but just thinking folks here would have some good ideas. Thank you Quote Link to comment Share on other sites More sharing options...
Phil Hancock Posted January 12, 2011 Share Posted January 12, 2011 The blade switches used on the old showmans engines will carry a lot of amps, IIRC Goliath was tested at something like 500 amps continious at 110v DC. Quote Link to comment Share on other sites More sharing options...
simonr Posted January 13, 2011 Share Posted January 13, 2011 Although a knife switch would look cool - in a sort of Frankenstein way, a relay / contactor would be simpler & likely cheaper! Si Quote Link to comment Share on other sites More sharing options...
Maverik Posted January 13, 2011 Share Posted January 13, 2011 It begs the question, whats it for? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 13, 2011 Share Posted January 13, 2011 You could always rob the controls out of a milk float...? I remember seeing the Scrapheap Challenge electric vehicle thingumy and it basically was a bunch of large open contacters... solid copper of course The other contactless way to do it is with MOSFETS or TRIACs, but probably more spendy that would like. BTW, did anyone notice on Mr Bowyers site that there's a winch with a solid state solenoid on it? (MOSFET) Not noticed it before... Quote Link to comment Share on other sites More sharing options...
simonr Posted January 13, 2011 Share Posted January 13, 2011 Alfred, Since you are a Carpenter, why don't you make a knife-switch base out of wood then if you can find some copper bar, make contacts which need to look like two 'L''s back to back, separated by the knife blade as you push it home. If you make the base and handle out of hard-wood, it's as good an insulator as Plastic for this purpose - and would look nicer too. Knife switches are good for high currents and voltages because the contact pressure is high and the as you switch it off, there is sufficient distance between the contacts to suppress arcing. They are still used in big power distribution systems, though generally pneumatically operated. Si Quote Link to comment Share on other sites More sharing options...
Night Train Posted January 13, 2011 Author Share Posted January 13, 2011 I am thinking of a zero budget reversing switch for a motor. No money to spend on contactors and don't like the 'CLUNK CLUNK' noise either. I have thought about wood, it was my first consideration but I wasn't sure how effective it would be in use compared to traditional insulators. I can look into that. I have lots of industrial switch gear to rob copper knife switch components from I think. I am thinking that if it can handle 200A 3ph then it should be fine at 200A dc if it is not actuated under load. Maybe a knife switch with the base in a 90deg V would be good, it would limit the swing of the handle. Quote Link to comment Share on other sites More sharing options...
nick w Posted January 15, 2011 Share Posted January 15, 2011 just for the record 200amps at 96v is very dangerous so dont construct anything to heath robinson also wood is not considered as an insulator as its obviously combustabale and conductive when damp paxalin is a product often is electrical switch gear as an insulator also your 200amps at 415v or 3 phase is very different to 200amps at 96v dc good luck Quote Link to comment Share on other sites More sharing options...
Night Train Posted January 15, 2011 Author Share Posted January 15, 2011 just for the record 200amps at 96v is very dangerous so dont construct anything to heath robinson also wood is not considered as an insulator as its obviously combustabale and conductive when damp paxalin is a product often is electrical switch gear as an insulator also your 200amps at 415v or 3 phase is very different to 200amps at 96v dc good luck The electrical dangers I am aware of so what I make will be 'safe' in that respect. I was more concerned about the moisture content in wood hence I was thinking of tufnol or similar. I need to work out what cross-sectional area I would need to handle the current. As I am not switching under load there won't be the arcing or contact erosion to worry about with it being DC. I have opened up some old isolator switch boxes and the blade switch elements don't look big enough based on my 'seat of the pants' feel for engineering components. It even comes down to 'knowing' that welder switches can handle the current and voltage but generally not for 30 minutes at a time. Maybe I will be investing in some Kilovacs or Albrights and faking the switch. Quote Link to comment Share on other sites More sharing options...
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