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electronic advice for dopes
http://byap.backyardmagazines.com/forum/viewtopic.php?f=10&t=3337		 Page 1 of 3
Author:  Jaymie [ Apr 26th, '08, 09:34 ]
Post subject:  electronic advice for dopes
okay, my brother is making us a backup power thingy, it will use a 200 amp hour deep cycle battery, an inverter and other stuff :?

He is having trouble sourcing a particular relay to use in it. He tends to build things that will NEVER fail, he would get on well with KP ;)

Can any one help by either sourcing one of these relays or by telling me which website to find it on.

Please don't tell me to try e-bay, I won't go there.

Alright, this is the description I got.

Quote:
A Mains Changeover Relay, with 2 x 240V coils. A mechanical interlock, one on other cannot be on. 2 open, 1 closed.


Does that make sense?

If anyone can help, please let me know.
Author:  Hex [ Apr 26th, '08, 10:51 ]
Post subject:  Re: electronic advice for dopes
Hi Jaymie,
Makes perfect sense :wink:
Sounds like you need something like this one, www.relayserviceco.com/relay3.htm
Can`t help with a supplier i`m afraid but at least you`ll know what your looking for.
Author:  Jaymie [ Apr 26th, '08, 11:11 ]
Post subject:  Re: electronic advice for dopes
thanks Hex :D
Author:  steve [ Apr 26th, '08, 16:28 ]
Post subject:  Re: electronic advice for dopes
jaymie, i have seen such relays during my time, but never ordered one. i'd say they are pricey!

If i may................whats the problem with using a normal DPDT relay?

below is a BLOCK diagram

inverter is always powered (but drawing minimal current in standby) and battery being kept charged via charger)

NO contacts of relay bridge mains to load as relay coil energized from mains

power fails

relay coil drops out and bridges NC contacts which link inverter to load. charger is not overloaded as it is off (no mains)

inverter operates at max load from batteries until power returns

$5 relay from many outlets.

Attachments:
block (Medium).JPG
block (Medium).JPG [ 33.99 KiB | Viewed 5289 times ]
Author:  steve [ Apr 26th, '08, 16:32 ]
Post subject:  Re: electronic advice for dopes
load (pumps) are without power for about 10milliseconds to 20milliseconds

If the idea is to ONLY run load when power fails then just dont connect mains to NO of relay! easy peasy. you can even put a switch on the former so you can switch between "run always" or "run on power out" :)
Author:  Jaymie [ Apr 26th, '08, 16:33 ]
Post subject:  Re: electronic advice for dopes
I don't know ;) I said I was a dope when it came to these things!

I'll send him the post and ask his opinion.
thanks
Author:  steve [ Apr 26th, '08, 16:34 ]
Post subject:  Re: electronic advice for dopes
not trying to second guess him, just offering help :)
Author:  KudaPucat [ Apr 26th, '08, 17:07 ]
Post subject:  Re: electronic advice for dopes
If you want it to last forever Jaymie (considering you mentioned me), I'd be using a contactor, they're indestructible. Ideally suited for motors and other high current devices. They come with the same features as a relay.
Ask him for me why he wants dual coil? I can understand the dual throw dual pole, but not the dual coil... unless he's super concerned about it never failing, afaik they're only used for safety circuits ;-)

Usually when I want one, I ask my sparky and he ends up just giving me one :-) isn't he nice. But he says they're only worth $15 or so, so not worth charging me. I guess I could try to source and send you one if you're desperate ;-)

This is approximately what you want: http://www.alibaba.com/product-gs/202973523/LC1_D_old_electrical_contactor.html
Author:  Uncle Yarra [ Apr 27th, '08, 11:16 ]
Post subject:  Re: electronic advice for dopes
Does it have to be brand spankers?
(I might have one but don't want to pull apart the supply if he wants a new one)
Author:  Jaymie [ Apr 27th, '08, 16:51 ]
Post subject:  Re: electronic advice for dopes
oooh, don't know, I'll check
Author:  Tony From West Oz [ Apr 27th, '08, 23:44 ]
Post subject:  Re: electronic advice for dopes
Jamie,
The only place I have seen those mechanically interlocked relays (contactors actually) is in standby diesel generators.

They are used to prevent the mains and the generator connecting together, even for a millisecond during the changeover from mains to generator or vice versa.
for an inverter based backup supply they would seem to be overkill.

A time delay (your fish and pumps would not be bothered by a 10 second changeover delay) could be used to delay the operation of 2 contactors, so that the mains was off for 10 seconds before changeover to inverter and when the mains returned, the loads would be disconnected from the inverter for 10 seconds before re-connection to the mains.


Just my 2c.

Tony
Author:  Jaymie [ May 2nd, '08, 05:00 ]
Post subject:  Re: electronic advice for dopes
Tony,
my brother has finally had a look at all the suggestions and *ta da* he thinks yours is the best bet ;)

Where would we get a changeover contactor please?
Author:  steve [ May 2nd, '08, 18:21 ]
Post subject:  Re: electronic advice for dopes
:sad10: mines not the bestest idea..............:sad10:
Author:  Uncle Yarra [ May 2nd, '08, 18:32 ]
Post subject:  Re: electronic advice for dopes
Isn't Steve's idea that same plus a timer for the relay?
Author:  steve [ May 2nd, '08, 18:39 ]
Post subject:  Re: electronic advice for dopes
: sort of, but you bring up a good point.

the time delays will need to be 12V powered!!!

seriously though, whats the problem with just the release delay of the contactor or relay?

KISS
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