From: "Peter Gottlieb"
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <_F1l9.30$VI5.firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com>
Subject: Re: (Avionics) How can this circuit produce an "inductive surge"?
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Date: Sun, 29 Sep 2002 01:52:40 GMT
NNTP-Posting-Date: Sat, 28 Sep 2002 21:52:40 EDT
"Tarver Engineering" wrote in message
> > Oh, I thought you were designing the power supply and/or protection. Is
> > 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.
> > 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, when
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
When I was at APC working on UPS systems the spec said the inverters had to
handle *any* load. I learned quickly to understand what that meant when the
VP of engineering brought in his table saw to test our new 1200 VA unit.
There may very well be commercial acceptance test specs and that is all fine
and good, but the real test is whether the avionics device is robust in the
real world, especially when the real world is a nasty place. Regardless of
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 it
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 this
But I digress. I got lost in the fog that this thread is becomming.