On Sun, Nov 3, 2013 at 2:41 PM, Lee Hart <[email protected]> wrote: > These look like acceptable relays for the application. I doubt that your 48v > contactor coils will draw over 0.6 amps.
Rated 0.35 momentary on contact, 0.1 constant current. > Note that the R in series with the relay coil for the time delay function is > still necessary. This R, together with the Capacitor across the relay coil > is what provides the RC time constant to delay the relay pull-in. Ah. I get it now. (I'm sure it's obvious that I have no formal background in circuit design and have picked up only dribs and drabs. I appreciate your patience!) [from another thread] > If you're worried about contact life, you can put a "snubber" across the > contact. > At this power level, it's a 0.1 ohm resistor and 1000uF capacitor in series > across the contact. The "resistor" in such a circuit is really just the > capacitor's > own ESR plus a pair of 6"-12" #24 wire leads on the capacitor. I can count on 10 weeks or so when I don't need to mow to do the initial conversion. Then each following year, I'll have another 10 weeks or so available if I have changes I want to make. I'm expecting fewer than 250 cycles per year, running the tractor 30-40 times total. Others are using this motor in a 48V configuration with only a contactor so I'm willing to gamble that it will last a year. The slow-start circuit has another very specific advantage of being a natural way to connect the existing safety lockout for engaged mower blades. I obviously don't want a cold start with the blades engaged. So I really like the idea of using that interlock. I think that for the initial conversion, I'll just start with a single snubbed contactor (this contactor may have a built-in snubber circuit, but if not it is clearly easy to follow your instructions...) since it's working for others. With that, I can hook in at least the seat safety interlock. Then I can plan to upgrade in the next off season to a more durable system based on your design which allows me to integrate more of the safety interlocks and has all the advantages we've discussed. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
