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From: john larkin <JL@gct.com>
Newsgroups: sci.electronics.design
Subject: Re: switchmode gyrator
Date: Wed, 13 Nov 2024 07:41:44 -0800
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On Wed, 13 Nov 2024 09:32:56 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

>john larkin <jl@glen--canyon.com> wrote:
>
>> On Tue, 12 Nov 2024 19:44:39 +0100, Jeroen Belleman
>> <jeroen@nospam.please> wrote:
>> 
>> >On 11/12/24 16:49, john larkin wrote:
>> >> On Tue, 12 Nov 2024 07:49:13 -0500, legg <legg@nospam.magma.ca> wrote:
>> >> 
>> >>> On Sat, 09 Nov 2024 06:08:40 -0800, john larkin <JL@gct.com> wrote:
>> >>>
>> >>>>
>> >>>>
>> >>>> Inductors are awful. Their energy storage is worse than electrolytic
>> >>>> caps by about a factor of 1000.
>> >>>>
>> >>>>
>> >>>>https://electronics.stackexchange.com/questions/326177/energy-density-
>> >>>>comparison-between-inductors-and-capacitors
>> >>>>
>> >>>> One could in theory make a switchmode gyrator that would make a
>> >>>> capacitor look like a programmable-value inductor.
>> >>>>
>> >>>> I have an application for that, but it would take too much engineering
>> >>>> and runtime complexity to make it worth doing. I guess I'll just have
>> >>>> to buy a bunch of giant, heavy custom toroids.
>> >>>
>> >>> I'm sure that there are other reasons why an inductor
>> >>> will be used besides the lack of time/energy/resources
>> >>> to 'design them out'.
>> >>>
>> >>> Energy storage is just one means to an end.
>> >>>
>> >>> RL
>> >> 
>> >> Sure. We want to design some dummy loads that will simulate relays,
>> >> solenoids, stepper motors, torque motors, with programmable R and L.
>> >> Seemed to me that using caps to make fake inductors would be a good
>> >> way to do that.
>> >> 
>> >> It's at least an interesting idea to play with. Maybe we can
>> >> switchmode simulate R+L all at once. We would have to store energy and
>> >> dissipate power to do that.
>> >
>> >Relays and motors do not behave like simple inductors. For example,
>> >while a relay armature is moving, the back EMF is high enough to
>> >make the current _drop_ briefly. Modelling that requires more than
>> >a simple gyrator.
>> >
>> >Jeroen Belleman
>> 
>> My customer is building giant rackmount boxes full of heavy inductors
>> as part of his dummy loads. We want to replace them.
>
>If space, weight and stray magnetic fields aren't a problem, big
>inductors can sometimes turn out to be remarkably cheap and efficient
>compared with more complex solutions.

We have learned that our customers care a great deal about rack space
and cables. And they used to have techs that built things like load
boxes, and when those old guys retired they didn't replace them.

We may make some smaller R+L dummy loads by switching real resistors
and tapped inductors. That is brain straining, especially specifying
the tapped inductors.

I was musing on designing a switchmode programmable synthetic R+L box
with essentially infinite programmable resolution, and using caps for
the energy storage instead of real inductors.

I suppose there can be a generalized impedance simulator.