Having fun at 350 amps

Sounds like fun, but a bit far afield for me. Good on you for posting it though!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

Consider, 250kW EV chargers run with currents over 500A, and that's continuous. Do we know how they work, familiar with the circuitry? Develop a little hands-on exposure, with free PCBs and low-cost parts. Yes, we're talking short current pulses, but you can get actual bench and 'scope experience with high di/dt. Email me your shipping address for free PCBs.

--
 Thanks, 
    - Win

Thanks, Win, but as I say it's a bit far afield, so it would probably just sit there on my bench. Plus I'm most unlikely to buy an electric car any time soon, or build a charger if I did.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

Thanks, Phil, Yes, I understand you're out, but I'm making a pitch to others. There's a pot on the board so you can adjust the current, from 5 or 10A upwards. Current pulses are very useful to test resistors, diodes, zeners, capacitors, inductors, MOSFETs, etc. Voltage pulses, such as you easily get from a switched MOSFET, don't work well, because V = L di/dt shields the part from high currents, until your wiring inductance charges up. Small L is a big deal at high di/dt.

The design uses specialized parts to reach 200A and above, but you can probably make it work to 25, 50 or 100A with ordinary on-hand parts.

--
 Thanks, 
    - Win

Here's a little laser driver

that was intended to drive a bar laser to pump a YAG. It can put 200 amps into a 25 volt stack at low rep-rates

We haven't sold many, because it's not horribly difficult to close a relatively slow current loop around a mosfet. It becomes a race-to-the-bottom price war, or the customer looks at the first article and says, hey, we can do that ourselves. We have more luck selling picosecond stuff at lower currents.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Sorry for the top-post. DropBox updates: Photos of little RIS-796 PCB and new measurements. Scope traces of nice pulses at 400, 500 and 560A. (These are with a 15mR load and 35-volt supply. Way more than the big LEDs can handle, but fun.) Also updated file sets for RIS-796 and RIS-796A.

Free PCBs start mail> Phil Hobbs wrote...

--
 Thanks, 
    - Win

Confirming, free shipping worldwide.

--
 Thanks, 
    - Win

Winfield Hill wrote in news: snipped-for-privacy@drn.newsguy.com:

That is not the stuff they used to contaminate telephone poles with is it? ;-)

Win, Sending that many amps via a pair of molybdenum electrodes is nice way to weld small copper wires to a pcb, no solder. (limit V to about 1.0). A good choice when you need a "clean" assembly. Cheers, Rich S.

Polychlorinated Biphenyls?

Win was talking about printed circuit boards, which are rather more enviroment-friendly.

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Bill Sloman, Sydney

Bill Sloman wrote in news: snipped-for-privacy@googlegroups.com:

It was a joke you retarded twerp.

Damn you are stupid.

BTW, Rob and I have extended our tests to much higher currents. Do you think a welding scheme like that would benefit particularly from precise current and pulse-length control? What's the story about limiting the maximum voltage?

--
 Thanks, 
    - Win

Programmable current would be nice for surface spot welding.

Y'mean this?

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Design 
Website: https://www.seventransistorlabs.com/

sues/

Looks interesting. Certainly better than the improvised high curent pulse g enerator i used back in the early '80s. I had just installed a new NiCad ba ttery pack in a Tektronix TDR. I told our techs that it had to be fully cha rged before the first use. One took it anyway, and left it in his work truc k over the weekend, with it turned on. All of the cells were shorted in tha t ~ $300 battery pack. I couldn't order a second one right away, and we onl y had the one TDR. I made the jerk hold the opened battery pack as I used a pair of jumper cables from his truck battery to blow out the whiskers as I reminded him that it could explode, each time I touched a cell. It was sti ll working, over three years later. :)

Not one that deserved to treated as a joke. Acronyms are frequently ambiguous, and making a joke out of the ambiguity takes more effort than you put in.

The retarded twerp here is you, wasting bandwidth with a poor excuse for a joke.

You do like to think so, but - as so you frequently do - you have misread the situation and drawn the wrong conclusion.

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Bill Sloman, Sydney

His six MOSFETs can handle about 4x more energy absorption in 1ms, than my big one with its heat sink, but for Frank Boeh's long pulses, say 55ms, they're a bit closer to equal, but his esr levels are much lower, and therefore the maximum currents with a given supply voltage are much higher. He's developed a very capable measurement and control system, with accessories, ideal for spot welding.

On the linked site,

--
 Thanks, 
    - Win

I've done 500A with a 20mR source resistor, and Rob has done 600A with a 10mR resistor. But we can use 5mR or lower, and apparently the MOSFET can handle over 1000A.** I've been wondering how they get datasheet Transfer Characteristics plots to 200A, etc, my SMU only goes to 10A. And hey, we'd like to get MOSFET operating data up to 1kA.

Aha, I realized we can easily do that. The next rev of RIS-796A (analog-control pulser) has 5mR resistor standard (1.0V at 200A), and changing a few parts lets it work to 1kA. The missing ingredient was an AD8274 difference amplifier, taking Vgs and translating this to ground, for precision measurement. Step current in 50 or 100A steps, and make measured Id vs Vgs graphs. Calculate the drain voltage and pulse duration to raise Tj to 175C, and get a high-temp plot. I'll be posting details shortly in a new thread.

** Our HUF75652 MOSFET can handle 33kW for 20us. We can make pulses as short as 2us.

--
 Thanks, 
    - Win

How about a lower RdsOn FET ? A 7 lead part, maybe the Infineon IPT015N10N5 100V 1.5 m Ohm I think it is also a bit larger die. Digikey has a bunch of them.

For high current shunts, 500A @ 50 mV is typically used or 1000A @ 100 mA shunts.

for Canadian Shunt 100 micro-Ohms

DELTEC is mainly who we use. Should be able to get these for less than $20 or so.