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From: Richard VanHouten
Subject: Re: (Avionics) How can this circuit produce an "inductive surge"?
Date: Thu, 03 Oct 2002 08:33:08 -0400
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Peter Gottlieb wrote:
> "Richard VanHouten" wrote in message
> > >
> > > Well, that makes some sense. But running a frequency converting MG set
> > > a UPS is not an optimal solution - why not just make the UPS run at the
> > > target frequency? The magnetics at 400 Hz are much lighter and
> > > than those required for 60 Hz, and the higher frequency makes other
> > > practical (eg, resonant).
> > The original product was the MG set (an import from Anton Piller Gmbh in
> > Germany), the front end inverter was our own design. IBM was
> > recommending the Piller MG sets for powering their then-current design
> > mainframes, so designing a stand-alone 400 Hz UPS would probably have
> > hurt business. The front-end inverter was a stand-by UPS; the MG set
> > ran directly off of mains during normal operation. Also, the inverter
> > had no magnetics to speak of; the MG set provided the power
> > conditioning.
> I forget that sometimes the business aspects take precedence over the
> engineering aspects. That always struck me as being somehow wrong even
> though with my business background I understand it.
> Yes, I've seen some larger systems with minimal magnetics, which can be done
> relatively easily when the bus voltages are high enough. I suppose if you
> are relying on the MG magnetics to be closely coupled to the inverter it
> would be an "interesting" problem dealing with the direct and reflected
> dynamics of the thing.
We were absolutely relying on the MG magnetics to be closely coupled to
the inverter; the inverter mounted on top of the MG control cabinet, and
we were relying on the MG to commutate off the SCRs in the inverter.
A seperate stand-alone 20A or 40A battery charger (which did have
significant magnetics) was used to charge the batteries.
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