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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: switchmode gyrator
Date: Wed, 13 Nov 2024 08:15:37 -0500
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On Tue, 12 Nov 2024 14:05:36 -0800, 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.
>
>Given a generalized switching impedance simulator, I guess one could
>model a DC motor.
>
>I am considering a powered impedance simulator, not the theoretical
>gyrator. Just sort of a gyrator.

Investing in heavy duty castors for the racks would get more 
bang for the buck.

RL