Resistance is futile. From: Chuck McCown via Af Sent: Wednesday, December 31, 2014 8:05 PM To: af Subject: Re: [AFMUG] Dc electric load ? Chuck ?
2 kW is some heat, no matter how you do it. Not sure if there are any common power transistors that can dissipate that much in a single device. If you parallel them then you have to ballast resistor them. Be nice to do full on and full off into a resistive load with input filtering. Then you could use smaller devices and heat sinks. PWM with input current feedback. From: Forrest Christian (List Account) via Af Sent: Wednesday, December 31, 2014 3:59 PM To: af Subject: Re: [AFMUG] Dc electric load ? Chuck ? The electronic way is a constant current source shunted to ground or through a resistor bank. One hefty npn power transistor and a few smallish components. Or a jfet with source tied to gate, with a current adjustment resistor in the source lead. Or any of a hundred circuits. For more wattage you can parallel several, each adjusted to take their fraction of the total amps. I seem to be slowly turning into a power electronics engineer over here. On Dec 31, 2014 3:42 PM, "chuck--- via Af" <af@afmug.com> wrote: I am thinking a DC-DC converter that will take a wide input and constant voltage output into a nice temperature compensated resistive load. What voltage range do you want? Doh!, that would be a constant power load. You want constant current load. Have to continue thinking... From: ch...@wbmfg.com Sent: Wednesday, December 31, 2014 3:39 PM To: af@afmug.com Subject: Re: [AFMUG] Dc electric load ? Chuck ? I know how to do it really cheap and easy under 2 amps. Have to think on this a bit. I have used hot water heating elements and coils of wire (in a bucket of water) for high wattage resistors but obviously not constant current. From: TJ Trout via Af Sent: Wednesday, December 31, 2014 12:11 PM To: af@afmug.com Subject: [AFMUG] Dc electric load ? Chuck ? Anyone know of a inexpensive do it yourself way to make a dc constant current electric load for testing power supplies, lithium batteries , etc ? Looking for something maybe 2kw+ and the cheapest premade thing I can find is $3500. Maybe I'll just use a carbon pile load but that will be much less accurate.
