interesting inductor

On a sunny day (Sun, 18 Aug 2019 09:31:18 -0700) it happened snipped-for-privacy@highlandsniptechnology.com wrote in :

I have no numbers on Joules, but been zapped plenty of times by 16 kV and 25 kV TV sets.

What makes a lot of noise is my 400 kV (bogus more like 40 kV) ebay Tesla coil:

That really depends on what you are doing

For motor drives, you need as much CM inductance as possible, since the DC link cap will take the DM noise. Granted, yes, a very little DM inductance can also be beneficial, for cost optimization

For other equipment, that has no real parasitic path to the surroundings, you need all the DM inductance you can get

Cheers

Klaus

That Schaffner cm inductor only has about 17 uH of leakage inductance. K > 0.999.

If it indeed saturates at a few mA of diff DC, an imperfect load, like an imperfectly timed triac for example, will make enough DC to saturate it.

Violet ray. Good at killing surface bugs & for vacuum work.

NT

You were seeing the energy from the huge capacitors they put on the output of the supply.

Just tried it with my supply, a single winding of a much larger CMC makes no additional spark compared to just shorting the leads (Lstray < 0.5uH). It also sparks on contact, not release. (The spark is rather more noticeable as I used a rather large adjustable switching supply, totaling something like 6mF on the output.)

Tim

The spark was when I disconnected the inductor. It was clearly an inductive kick from energy stored in the L. Disconnecting a dead short from that 2 volt supply would not make a spark. Its output caps would start from zero volts and begin to recharge towards 2 volts.

One term in use when an inductor is disconnected is "break flash."

Wild guess, 1 mJ would make a visible spark, but 1 uJ wouldn't.

It would be cool if you could use one set of windings for the taps on the DAC, and the other to push a DC current thru biasing them so they're on the cusp of saturation, and use some kind of feedback to detect the DAC linearity and feed back the right currents to each to dynamically adjust their inductances, so you get a nice inductive DAC out of maybe just a couple values instead of having to parallel/series together the appropriate ones for the exact value for each tap

This is a large-signal (very large signal!) application. Some PM alternator regulators work by shorting the generator, which PM alternators tolerate because they have a lot of inductance.

We may get away with using a single, maybe 1 mH, inductor and doing DSP inductor simulation behind that. There's remarkably little data around on actual alternator impedances, or details on how the regulators actually work.

It's annoying that there are a goodly number of papers and thesies around about alternators, full of equations and matrices and all that fancy math, with no actual numbers. That's typical of most scientific papers, lots of theory but no useful numbers.

I think I'll buy a few alternators and spin them up, just to get in the ballpark.

I found a use for a gyrator! I am working on a thing for a client that has a tuned circuit in a feedback network with an inductor to ground. to meet the requirement it has to be tuned very precisely and I could continue grunging math but I think I'm just going to make it a two op amp "inductance simulator", make one of the relevant resistors a pot and say "turn this knob until it works the way you like."

I found a paper a while back that was a mathematical model of how much current an average small car (of the time) with an I4 or something draws at cranking, it doesn't look like this problem was even approached in an academic way via maths/computational numerical methods until the late

Put battery and alternator in car. If it starts reliably, great. If not get somewhat bigger battery and alternator. Repeat until satisfied.

Well within a couple uH should be fine.

You can also use a variable gain < 1, to bootstrap the low end of a real inductor and trim its effective value. That works with resistors and caps, too.

That was actually patented until 2015 lol

It wouldn't surprise me if people were doing that in the 1930's.

Bootstrapping impedance or getting patents for obvious things approved? Both, I guess.

I recall I saw a patent from olden times (when the vacuum tubes in schematics looked like Egyptian hieroglyphics and the resistor symbols were drawn with all right-angles) where they ran the heater current thru a second winding on the power supply filter choke somehow to bootstrap its effective value, that was probably worth a patent in 1932.

Another approach is to generate a 90 degree phase shifted version of the current in the inductor and use a Wien bridge type feedback circuit to add that to the current coming out of the inductor (or subtract from it).

This creates an additional positive or negative synthetic inductance, and lets you tune the frequency as finely as you can tweak the gain.

I've got a bunch of simulations doing that around 17kHz (100,000 radians per second, which keeps the arithmetic simple).

I dumped it when my collaborator in the UK pointed out that hysteresis in even a heavily gapped ferrite core inductor was going to introduce harmonics 95dB below the fundamental.

Bootstrapping can also turn a resistor into an inductor or a capacitor or a resistor bigger or smaller than its usual value.

"Dynamic" speakers had electromagnets, instead of permanant magnets, and the field current was reused for filament power, or the field coil was also a power supply choke.

I have a bunch of radio engineering books, starting in 1922.

Good grief, that's almost 100 years.

There's zillions of adjustment methods documented in the famous RDH4, this probably included.

Tim

On a sunny day (Sun, 18 Aug 2019 12:52:03 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in :

Yes, that would work, ozone,, I use an EPROM erase tube for that:

I noticed somebody on TV using it to purify water, this sort of product:

VRs are good for most skin issues. Water can be sterilised just by putting it in a plastic bottle in the sun.

NT