300W Resistive load?
in [Design]
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From: Vladimir Vassilevsky on 18 Jul 2010 11:43 Joerg wrote: > Hammy wrote: > >>What is something cheap and simple that can be used to dissapate 300W >>on a 200Vdc bus. I'm trying to think of something I could maybe pick >>up at a local homedepot or similiar. >> >>I need a 300W load to test out my PFC. > Take a 25W wirewound resistor and put it into a bucket of water. > > Light bulbs? Two in series and then as many of those in parallel as needed. IIRC John Fields posted some measurements on the transient behavior of the incandescent lightbulbs. There is huge inrush current (~x10 of nominal) for few dozens of milliseconds. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
From: Nico Coesel on 18 Jul 2010 11:40 "Tim Williams" <tmoranwms(a)charter.net> wrote: >"Nico Coesel" <nico(a)puntnl.niks> wrote in message = >news:4c42bd4b.224380781(a)news.planet.nl... >>>What is something cheap and simple that can be used to dissapate 300W >>>on a 200Vdc bus. I'm trying to think of something I could maybe pick > ^^^^^^ >>>up at a local homedepot or similiar. >>> >>>I need a 300W load to test out my PFC. >>=20 >> I've constructed an adjustable dummy load by using 4 TO3 transistors >> from an old switching power supply. A heatsink and a couple of fans >> take care of the heat. The whole thing isn't much larger than a shoe >> box. > >Doesn't work in this case though, you'll be in the second breakdown = >region. Unless it was slightly less old and used TO-3 MOSFETs, which = >Idunno, might be worth something on eBay. :^) If you use transistors that can handle 200V (or way more) like I did there is no problem. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico(a)nctdevpuntnl (punt=.) --------------------------------------------------------------
From: Tim Williams on 18 Jul 2010 14:31 "Nico Coesel" <nico(a)puntnl.niks> wrote in message news:4c431fff.249648812(a)news.planet.nl... > If you use transistors that can handle 200V (or way more) like I did > there is no problem. I'm just wondering if they were MOSFET or bipolar. TO-3 MOSFETs are somewhat old and rare. MJ15025 for instance won't handle more than 0.17A at 200V, according to the SOA, which is only 34W, out of a rated 250W. The average HOT may do. Then again, maybe not; 2SC5404 shows only 0.11A at 200V. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: Jan Panteltje on 18 Jul 2010 15:20 On a sunny day (Sun, 18 Jul 2010 13:31:49 -0500) it happened "Tim Williams" <tmoranwms(a)charter.net> wrote in <pMH0o.19915$lS1.3321(a)newsfe12.iad>: >I'm just wondering if they were MOSFET or bipolar. TO-3 MOSFETs are = >somewhat old and rare. MJ15025 for instance won't handle more than = >0.17A at 200V, according to the SOA, which is only 34W, out of a rated = >250W. > >The average HOT may do. Then again, maybe not; 2SC5404 shows only 0.11A = >at 200V. > >Tim TO3 MOSFET BUZ44A 4.8A 600 V (siemens) Was quite common. I used hundreds.
From: Tim Wescott on 18 Jul 2010 15:43
On 07/17/2010 06:36 AM, Hammy wrote: > What is something cheap and simple that can be used to dissapate 300W > on a 200Vdc bus. I'm trying to think of something I could maybe pick > up at a local homedepot or similiar. > > I need a 300W load to test out my PFC. 1: Several space heaters of like wattage, all in series (assuming that their power consumption is in the 1kW range). 2: Several incandescent light bulbs. If you live in a 120VAC country, make series pairs and connect pairs in parallel until you're drawing your desired current. If you live in a 240VAC country, just use single bulbs, adding them in parallel until you're happy. They'll draw somewhat less current, because of the lower voltage, but it won't be a simple 200/240 relationship because they'll run cooler and therefore with lower resistance. So, e.g., three sets of two parallel 50W, 120V light bulbs should burn off something around 280 or 290W. Ditto three 100W, 240V bulbs. Fine tune with 7W night light bulbs, and maybe 25W refrigerator bulbs. 12V car bulbs would work, too, but you'd need a string of 16 in series to get up to 200V; figuring out which bulbs to get -- if there are any small enough to be suitable -- is left as an exercise to the reader. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |