No wattages are listed. I wonder what they can dissipate. I wonder what the resistance element is. Iron? Stainless? I doubt nichrome but could be. Too bad they didn’t include batteries. Maybe they are AC only.
From: Ken Hohhof via Af Sent: Wednesday, December 31, 2014 9:28 PM To: [email protected] Subject: Re: [AFMUG] Dc electric load ? Chuck ? I always found it interesting that most diesel electric locomotives use dynamic braking and dissipate the electricity in resistor banks near the roof with fans to cool them. So you could buy some of these: http://www.mosebachresistors.com/resistors_rl.html 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" <[email protected]> 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: [email protected] Sent: Wednesday, December 31, 2014 3:39 PM To: [email protected] 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: [email protected] 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.
