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Continuous duty contactor wiring question

 
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nuckollsr(at)cox.net
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PostPosted: Sat Mar 04, 2006 8:33 am    Post subject: Continuous duty contactor wiring question Reply with quote

At 01:32 PM 3/4/2006 +0100, you wrote:

Quote:

<mick-matronics(at)rv8.ch>

Hi,

I've got a S701-1 contactor I purchased from B&C
http://www.bandc.biz/S701-1.html which I want to
use in a slightly different application.

I want to use it as suggested by Eric with his
OVP module. http://www.periheliondesign.com/LOVM.htm

The wiring for his OVP module requires that I
use the 12v line as the contactor control, not
the ground wire used in the battery contactor
application.

Does Eric recommend this contactor for use with
his product? Last I heard, the high-voltage
EV series contactors were his associated product
of choice.

Quote:
I've read the battery contactor information in
chapter 8 several times, but I still really
don't quite understand the role of the spike
suppression diode, nor whether or not I will
need one.

See http://aeroelectric.com/articles/spikecatcher.pdf

Quote:
Should I use the spike suppression diode?
Should it be installed between the two
coil terminals?

What does Eric's installation drawings/instructions
say? He might have built the spike suppression diode
into the electronics. Perhaps his design does not
benefit from the diode or may even be detrimental
to it's intended function.

Remember folks, questions like this are ALWAYS
best addressed to the designer/manufacturer
of the product. It's risky and sometimes unethical
to inject ourselves into the relationship between
customer and supplier until it's determined
that the supplier simply doesn't know the answer
to your question or in some cases, is simply wrong.

Study the drawings, discuss your uncertainties
with the supplier. If you're not satisfied or
still skeptical, then go to the List for whatever
clarification and assistance may be available.

Quote:
If so, does it matter
which terminal is (+) and which is (-)?

Absolutely. The banded end of the diode
faces the (+) terminal of the contactor.
Reversing the diode may cause serious
fault currents to flow and damage something.

Bob . . .

< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >


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nuckollsr(at)cox.net
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PostPosted: Wed Mar 08, 2006 10:21 am    Post subject: Continuous duty contactor wiring question Reply with quote

At 06:25 PM 3/8/2006 +0100, you wrote:

Quote:

<mick-matronics(at)rv8.ch>

> Remember folks, questions like this are ALWAYS
> best addressed to the designer/manufacturer
> of the product. ...

You are right. I was thinking of the product as
the contactor, and Eric's product as a switch.
In any case, Eric has a nifty product to protect
the coils from doing whatever bad thing it is
that they do.

In this case, systems integration issues go
beyond the magnetic field collapse in the
coils. Folks here on the list have raised
legitimate issues with respect to the contactor's
ability to reliably open a runaway alternator's
output. This has almost nothing to do with
the coil circuit and everything to do with
contact spreading velocity and ultimate gap
(or double gap) distance in the open contactor.

If Eric or anyone else has called out this
class of contactor as suited to the task when
combined with his product, then other folks
here on the list are ill prepared to dispute
it without an exchange of simple ideas that
support (or fail to support) the manufacturer's
design decision.

Therefore questions going to suitability
to task must to start with folks who
offer the product. If the simple-ideas
don't assemble correctly, others with knowledge
and experience can illuminate the errors
of logic.

Until I'm apprised differently, I can only
say that based on objections raised earlier
(for which we've seen no test data to the
contrary) I am skeptical of this contactor's
ability to handle the task (Note 1). I'd be delighted
to have that skepticism put to rest but
I'm not presently in a position do it myself.

Bob . . .
Note 1. The "task" is to make/break the b-lead
of an alternator under a variety of conditions
the most important of which is OV management.
If the contactor is expected to be damaged in
an OV management event, so be it as long as the
event is handled to the benefit of the rest of
the airplane's systems. There are less stressful
make-break issues too. I would expect anyone who
recommends a device for this service to be capable
of articulating the capabilities and LIMITS of the
system.


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ajrow(at)westnet.com.au
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PostPosted: Wed Mar 08, 2006 3:10 pm    Post subject: Continuous duty contactor wiring question Reply with quote

Robert L. Nuckolls, III wrote:

Quote:
In this case, systems integration issues go
beyond the magnetic field collapse in the
coils. Folks here on the list have raised
legitimate issues with respect to the contactor's
ability to reliably open a runaway alternator's
output. This has almost nothing to do with
the coil circuit and everything to do with
contact spreading velocity and ultimate gap
(or double gap) distance in the open contactor.

Out of curiosity, would a large capacitor across the contactor similar
to points ignition help? Or is there too much energy involved for a
reasonably sized capacitor to absorb?

--
Andrew Rowley
ajrow(at)westnet.com.au


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