[ausev] sizing wire and relays

[jefoy at mindspring.com]

You can try golf cart manufacturers - they should have something as they are typically 36 volt systems. A contactor or relay rated for DC needs a magnetic blowout device, that is a permanent magnet used to divert the plasma that forms as the contacts open. If this is a main circuit interuption device you need to plan for a fail mode that leaves the motor controller on at full power meaning you need to be able to interupt at maximum current safely.

It might seem overkill but the contactors from Kilovac are designed just for that type of application:
http://relays.tycoelectronics.com/datasheets/ap90.pdf

For wire sizing, in large part it is more of a performance issue, for a 110 V house wire, a 2 volt drop is hardly noticeable. In a 36V EV application, 2 volts is 5.5% of the total. In a purely resistive load that is 11% loss in power.



-----Original Message-----
>From: MLAB <info at easystreetrecumbents.com>
>Sent: Mar 13, 2006 6:17 AM
>To: AusEV <ausev at austinev.org>
>Subject: [ausev] sizing wire and relays
>
>Thanks for the directing me to the wire gauge chart.  I reckon I will 
>just buy a lot of 10g wire from Breeds and use that.  The analogy to the 
>pipes is helpful as well.  I always add extra layers of insulation to 
>all my wires for crash safety and the like.
>
>Regarding the relays, it appears from the posts that the main concern is 
>how safe it is to switch the relay at full power, while I can likely 
>make something smaller do for switching with the throttle off.  But in 
>the interest of safety, can anyone direct me to a good source for relays 
>capable of switching higher amp DC loads?
>
>I see a variety of "automotive relays" in the Mouser catalog, but these 
>never specify DC or AC.  It would be nice if there were such a catalog 
>that had DC electric motor users in mind.
>
>-- 
>Mike Librik, LCI #929
>Easy Street Recumbents
>(512) 453-0438
>45th and Red River Streets, thereabouts
>Central Austin
>info at easystreetrecumbents.com
>www.easystreetrecumbents.com
>www.urbancycling.com
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