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From: "Tarver Engineering"
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <_F1l9.30$VI5.email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
Subject: Re: (Avionics) How can this circuit produce an "inductive surge"?
Date: Sat, 28 Sep 2002 19:02:40 -0700
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
"Peter Gottlieb" wrote in message
> "Tarver Engineering" wrote in message
> > > Oh, I thought you were designing the power supply and/or protection.
> > > adequate protection still a poor assumption to make? I'm not really
> > > where you're coming from here.
> > The airplane is already designed and built.
> > For the power supplies I design the input to, the transients are
> Ah, I *thought* we were going in circles.
The fact that I design in a way such as to eliminate transients in no way
should lead to an assumption that all others do the same.
> > > I would think an isolated power supply would give the best protection.
> > > way it only cares about the input bus voltage and not noise between
> > +
> > > or - lead and ground. Proper design would survive the environment
> > > for (you mentioned some spec), whether this included 600 Volt spikes,
> > > reverse polarity, or whatever.
> > Sure, but you can't know that for an existing airplane.
> > In fact, the manufacturer seems to disagree with you.
> Well, maybe my kind of engineering is different, but where I come from,
> something is supposed to be able to handle a given quality of raw power
> input it had better be able to demonstrably do so or it was back to the
> drawing board.
That is the basic function of RTCA DO-160, but that is no guarantee that the
entire airplane meets the spec.
> When I was at APC working on UPS systems the spec said the inverters had
> handle *any* load. I learned quickly to understand what that meant when
> VP of engineering brought in his table saw to test our new 1200 VA unit.
It would seem your specs are gibberish.
> There may very well be commercial acceptance test specs and that is all
> and good, but the real test is whether the avionics device is robust in
> real world, especially when the real world is a nasty place. Regardless
> what the plane manufacturers say, if a device is properly designed then it
> will withstand the airplane environment. There may be other reasons for
> them to make their procedures as they are that are perfectly valid, but on
> this specific point, in the throretical sense, what I say is accurate as
> is a matter of definition. In a practical sense, knowing the nasty spikes
> can exist on starting, one would be a fool to leave avionics on during
Leaving the avionics bus off during starting would be the best way and
shutting the avionics bus off at shutdown would be a good way to increase
the probability that the avionics bus is off during a start.
> But I digress. I got lost in the fog that this thread is becomming.
It is the crosspost.
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