[ausev] a question about fuses

[jefoy at mindspring.com]

The problem with fuses, as with relays, is the use of DC as opposed to AC voltages. In an AC system , the voltage reverses polarity at whatever the frequency of the system is, limiting the potential duration of an arc since the voltage will go to zero several times a second. In a DC system, as a fuse opens (or relay contact) a plasma is formed at the breaking contact surfaces and the ionized air between the contacts acts as a low impedance path to continue to conduct current. The plasma can exist as long as a potential exists between the contacts unless there is an external means of quenching the arc. In a high voltage relay this is done by using a permanent magnet to bend the ion stream away from the contacts  when the circuit opens or by keeping the contacts in a vacuum so the plasma cannot form. In high voltage fuses, the body of the fuse cavity is filled with sand or something similar, the material acting to quench the arc when the fuse opens.  I have seen fuses typically rated to 600 VAC, I don't recall their DC rating..

See this article for reference to fuses up to 60A:
 http://www.littelfuse.com/data/en/Technical_Articles/EVAX.pdf
See also:
http://www.solarseller.com/dc_fuses_and_holders__ul_listed_and_non_ul_listed_.htm



-----Original Message-----
>From: MLAB <info at easystreetrecumbents.com>
>Sent: Mar 6, 2006 8:56 AM
>To: AusEV <ausev at austinev.org>
>Subject: [ausev] a question about fuses
>
>I want to put some fuses in my battery packs.  These are all 36V and 48V 
>packs.  However, when I look through the Mouser catalog, I see that the 
>high amp fuses only go up to 32V, while the fuses that can handle 
>anything more than that max out at about 15A.
>
>Is there a better source for fuses for EV applications?  (Probably, but 
>I am just used to ordering everything from Mouser).  Could one take two 
>lower voltage fuses and run them in parallel to put a higher voltage 
>through them?
>
>Thanks for any input...
>
>
>-- 
>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
>_______________________________________________
>AusEV mailing list
>AusEV at austinev.org
>http://www.austinev.org/mailman/listinfo/ausev