1 - 2 of 2 Posts

#### EVDL List

· Registered
Joined
·
72,624 Posts
Discussion Starter · ·
Hi all,

I have a question about a 28v contactor I have on my go-kart, it currently
runs on 24v, but I hope to upgrade the kart
to 36v, the contactor should be ok on this also right ? considering that
voltage will sag a bit ...
Or should I find a voltage reduction circuit ?

dave
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20101025/0bfc89db/attachment.html
_______________________________________________
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev

#### EVDL List

· Registered
Joined
·
72,624 Posts
Discussion Starter · ·
Dave Hymers wrote:
> I have a question about a 28v contactor I have on my go-kart, it
> currently runs on 24v, but I hope to upgrade the kart to 36v, the
> contactor should be ok on this also right? considering that voltage
> will sag a bit... Or should I find a voltage reduction circuit?

A contactor coil will generally work from 75% to 125% of rated voltage.
Check the manufacturer's data sheet for the precise values for your
particular contactor.

36v on a 28v coil is 128%, so I would do something to reduce the
voltage. A good method is to put a parallel R-C network in series with
the coil (called a "slugger" circuit).

When first powered, the capacitor is discharged so the coil gets the
full supply voltage. This makes it pull in fast, which is good for
reducing contact wear.

Then the capacitor charges, and the falls to whatever the resistor
allows. Choose the resistor to provide a lower "holding" current,
typically 50% of the coil's rated on-state current. Choose the capacitor
to give you about a 50 msec time constant. This makes the coil run about
4 times cooler (saves power, good for coil life), and also lets it drop
out faster (good for contact life).
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

_______________________________________________
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev

1 - 2 of 2 Posts