We have been presented with an engineering problem that we are not sure how to solve: we need to be able to measure high-frequency ripple current (up to several MHz) on a DC power rail that can be anywhere from zero to 500 volts, and get that in a form that can be fed into a logging device. The DC component of the current can be up to 100 amperes. Any engineers here who can give some advice?
@Felthry Any specific logging device or are you rolling the entire solution?
@zetasyanthis probably going to use an oscilloscope and possibly also a some sort of dSPACE unit or equivalent
but it's been pointed out to us that we're kind of getting ahead of ourselves here and we need to do the basics before worrying about metrology
@Felthry Also re: this, can current transformers not give you high enough bandwidth?
@zetasyanthis our target is 30MHz, and it's going to be on top of a DC bias of 100A--that's going to saturate most cores
@Felthry Ah, I hadn't thought about the saturation issue. Hmm.
@zetasyanthis We considered a Rogowski coil, which is essentially just an air-core current transformer, but, well. Air-core.
@Felthry Hmm. What kind of resolution do you need?
@zetasyanthis Our lab (unfortunately) uses Tektronix scopes mostly (we don't like tektronix as much as agilent (no, keysight is a bad name, I'm calling it agilent)), so let me see if they make one of those...
@Felthry I don't see why tek vs. agilent is an issue there? It just outputs a BNC. And there's a whole series, looks like. https://www.keysight.com/en/pc-1659326/oscilloscope-current-probes?cc=US&lc=eng
@zetasyanthis current probes almost always use some proprietary connector on top of the BNC though? I know the current probes we have already can let you know when the jaw is open for example
@Felthry "Compatible with any Keysight oscilloscope with a 1 MΩ input BNC" (Which means any. The picture shows a normal BNC cable.)
@Felthry If you click on the link, you'll see. :P 600A, 30Mhz.
@zetasyanthis Ah, didn't realize I had to enable javascript to see the iamge, that's weird
@Felthry Oh, that kinda is. Either way, I think that does what you want? There's a 300A model too. Not sure on the resolution. You'll have to check.
@zetasyanthis Possibly! The price is a bit ehhhh though--we'll focus on designing the buck converter first and then get around to metrology. Will leave a spot for current measurements.
Fair. Keysight's stuff is pricey, but it's good at least.
I'm also a little curious what this is for. I've designed buck regulators before (and was actually working on a few just the other day), but 100A is quite a bit.
@zetasyanthis you managed to lose the @!
Research on three-level buck converters, specifically circulating currents when using multiple in parallel, as well as how to mitigate problems with neutral point drift.
This is based around DC power transmission systems, as used on some ships. The idea is that this small(!) device will have a 10kW max power output
@Felthry I feel you 100%. I used to work for the IC (at one of their contractors) and left that forever after they used one of my devices to launch air strikes at people. :(
@Felthry (Technically they gave it to a third party government who then did what they wanted with it, but that's still not what I signed up for, or was okay with.)
@zetasyanthis fortunately I think working on power systems and only power systems is mostly guilt-free as long as it's not classified research. It's a generic enough thing that it's applicable to pretty much _anything_, I guess?
@Felthry Yeah, that's fair. I stayed on for a while doing some work for NASA for similar reasons.
@Felthry And mine research and development definitely was classified, hence not saying exactly who it was for. :/
@Felthry Actually, I suppose I should say "a different organization in the IC," since ONI definitely qualifies.
@zetasyanthis The research is being done on a grant from the office of naval research so of course it'd be about shipboard stuff (not a huge fan of working on a thing for the navy, but none of this is classified research and all of it will apply equally to freight ships so....)