300W Resistive load?
in [Design]
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From: krw on 17 Jul 2010 18:57 On Sat, 17 Jul 2010 18:26:42 -0400, Hammy <spam(a)spam.com> wrote: >On Sat, 17 Jul 2010 17:21:39 -0500, "krw(a)att.bizzzzzzzzzzzz" ><krw(a)att.bizzzzzzzzzzzz> wrote: > >[SNIP] >>Try buying a real toilet. Well, if you don't live near a Canuckistani >>HomeDespot. > >Yea we have Mohawks running bootleg booze and smokes across the lake >and yanks smuggling toilets back the other way.;-) Balance of bootleg, er, trade. ;-)
From: Grant on 17 Jul 2010 19:30 On Sat, 17 Jul 2010 09:25:42 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Hammy wrote: >> On Sat, 17 Jul 2010 07:37:28 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> Hammy wrote: >>>> On Sat, 17 Jul 2010 07:00:35 -0700, Joerg <invalid(a)invalid.invalid> >>>> 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. >>>>> Light bulbs? Two in series and then as many of those in parallel as needed. >>>> Sounds good one 60W bulb is about 200 ohms. ... >>> >>> At 200V each bulb gets only 100V so the resistance will be a little >>> lower. You could measure that if it must be precise. >> >> I don't need high precision if I can test at even 80% rated load and >> maybe do some pulse test and off course use a CT to check the input >> current I'll be happy. > > >Well, just wanted to mention that because when at undervoltage the bulbs >will present a higher load. Also, when you start any kind of converter >from zero they will almost look like a short initially. Same if you >connect a cold bulb (cold filament) to a running converter. It's not >like a power resistor. > > >>>> ... I'll look around for some small cheap bulb mounts. >>> >>> You can also solder to them. If careful they can later still be used for >>> their intended purpose. But make sure you place them onto a heat >>> resistant surface during the test :-) >> >> Your taking all the fun out of this :-) >> > >The fun might come back when connecting the cold bulbs not two by two, >but all at once. Tchk ... *POOF*. Decent converter should handle that? Not like 8:1 lamp hot:cold is a short circuit, almost a short ;) I keep an old fuser element in the cupboard for hi voltage loads, and have light bulbs setup for 24V with 12V halogens in series, then proper high wattage resistors picked up over time. Lamps are easiest to hook up, perhaps three or more in series at first? Over here they've banned incandescent lamps already, only those new and expensive hi-voltage halogens available :( What about an electric heater on low? Got a couple or more to wire in series? Raid an electric stove, put elements in series? > > >>> Good news is you may not even have to drive all the way to Home Depot. >>> Supermarkets also have a variety of them. Of course, then your wife >>> might hand you a lengthy "while you are there anyhow" list and you don't >>> get to look at all the new power tools, barbecues and stuff. Man's toy >>> store ... >> We call that a honey do list here.;-) >> > >Nah, a honey-do list isn't grocery shooping, it's when the missus wants >you to get that tree stump out over yonder, and it's 105F :-) Grant.
From: Jim Thompson on 17 Jul 2010 20:06 On Sun, 18 Jul 2010 09:30:22 +1000, Grant <omg(a)grrr.id.au> wrote: >On Sat, 17 Jul 2010 09:25:42 -0700, Joerg <invalid(a)invalid.invalid> wrote: > >>Hammy wrote: >>> On Sat, 17 Jul 2010 07:37:28 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> Hammy wrote: >>>>> On Sat, 17 Jul 2010 07:00:35 -0700, Joerg <invalid(a)invalid.invalid> >>>>> 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. >>>>>> Light bulbs? Two in series and then as many of those in parallel as needed. >>>>> Sounds good one 60W bulb is about 200 ohms. ... >>>> >>>> At 200V each bulb gets only 100V so the resistance will be a little >>>> lower. You could measure that if it must be precise. >>> >>> I don't need high precision if I can test at even 80% rated load and >>> maybe do some pulse test and off course use a CT to check the input >>> current I'll be happy. >> >> >>Well, just wanted to mention that because when at undervoltage the bulbs >>will present a higher load. Also, when you start any kind of converter >>from zero they will almost look like a short initially. Same if you >>connect a cold bulb (cold filament) to a running converter. It's not >>like a power resistor. >> >> >>>>> ... I'll look around for some small cheap bulb mounts. >>>> >>>> You can also solder to them. If careful they can later still be used for >>>> their intended purpose. But make sure you place them onto a heat >>>> resistant surface during the test :-) >>> >>> Your taking all the fun out of this :-) >>> >> >>The fun might come back when connecting the cold bulbs not two by two, >>but all at once. Tchk ... *POOF*. > >Decent converter should handle that? Not like 8:1 lamp hot:cold is >a short circuit, almost a short ;) > > >I keep an old fuser element in the cupboard for hi voltage loads, and >have light bulbs setup for 24V with 12V halogens in series, then proper >high wattage resistors picked up over time. > >Lamps are easiest to hook up, perhaps three or more in series at first? > >Over here they've banned incandescent lamps already, only those new and >expensive hi-voltage halogens available :( > >What about an electric heater on low? Got a couple or more to wire >in series? Raid an electric stove, put elements in series? >> >> >>>> Good news is you may not even have to drive all the way to Home Depot. >>>> Supermarkets also have a variety of them. Of course, then your wife >>>> might hand you a lengthy "while you are there anyhow" list and you don't >>>> get to look at all the new power tools, barbecues and stuff. Man's toy >>>> store ... >>> We call that a honey do list here.;-) >>> >> >>Nah, a honey-do list isn't grocery shooping, it's when the missus wants >>you to get that tree stump out over yonder, and it's 105F :-) > >Grant. I've been known to take two sheets of copper clad, drill a grid of holes and solder a hundred or so 2W resistors between the planes, put a muffin fan on it and away you go... :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Friday is Wine and Cheeseburger Day
From: Grant on 17 Jul 2010 20:25 On Sat, 17 Jul 2010 17:06:10 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >On Sun, 18 Jul 2010 09:30:22 +1000, Grant <omg(a)grrr.id.au> wrote: > >>On Sat, 17 Jul 2010 09:25:42 -0700, Joerg <invalid(a)invalid.invalid> wrote: >> >>>Hammy wrote: >>>> On Sat, 17 Jul 2010 07:37:28 -0700, Joerg <invalid(a)invalid.invalid> >>>> wrote: >>>> >>>>> Hammy wrote: >>>>>> On Sat, 17 Jul 2010 07:00:35 -0700, Joerg <invalid(a)invalid.invalid> >>>>>> 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. >>>>>>> Light bulbs? Two in series and then as many of those in parallel as needed. >>>>>> Sounds good one 60W bulb is about 200 ohms. ... >>>>> >>>>> At 200V each bulb gets only 100V so the resistance will be a little >>>>> lower. You could measure that if it must be precise. >>>> >>>> I don't need high precision if I can test at even 80% rated load and >>>> maybe do some pulse test and off course use a CT to check the input >>>> current I'll be happy. >>> >>> >>>Well, just wanted to mention that because when at undervoltage the bulbs >>>will present a higher load. Also, when you start any kind of converter >>>from zero they will almost look like a short initially. Same if you >>>connect a cold bulb (cold filament) to a running converter. It's not >>>like a power resistor. >>> >>> >>>>>> ... I'll look around for some small cheap bulb mounts. >>>>> >>>>> You can also solder to them. If careful they can later still be used for >>>>> their intended purpose. But make sure you place them onto a heat >>>>> resistant surface during the test :-) >>>> >>>> Your taking all the fun out of this :-) >>>> >>> >>>The fun might come back when connecting the cold bulbs not two by two, >>>but all at once. Tchk ... *POOF*. >> >>Decent converter should handle that? Not like 8:1 lamp hot:cold is >>a short circuit, almost a short ;) >> >> >>I keep an old fuser element in the cupboard for hi voltage loads, and >>have light bulbs setup for 24V with 12V halogens in series, then proper >>high wattage resistors picked up over time. >> >>Lamps are easiest to hook up, perhaps three or more in series at first? >> >>Over here they've banned incandescent lamps already, only those new and >>expensive hi-voltage halogens available :( >> >>What about an electric heater on low? Got a couple or more to wire >>in series? Raid an electric stove, put elements in series? >>> >>> >>>>> Good news is you may not even have to drive all the way to Home Depot. >>>>> Supermarkets also have a variety of them. Of course, then your wife >>>>> might hand you a lengthy "while you are there anyhow" list and you don't >>>>> get to look at all the new power tools, barbecues and stuff. Man's toy >>>>> store ... >>>> We call that a honey do list here.;-) >>>> >>> >>>Nah, a honey-do list isn't grocery shooping, it's when the missus wants >>>you to get that tree stump out over yonder, and it's 105F :-) >> >>Grant. > >I've been known to take two sheets of copper clad, drill a grid of >holes and solder a hundred or so 2W resistors between the planes, put >a muffin fan on it and away you go... :-) Yup, fairly easy to make and use. I'm doing something like that with 17W resistors for a hybrid power DAC I'm building. Except I'm using a strip of copper clad each end of 8 x 17W resistors, and they'll be bolted to a framework made with M5 allthread and spacers with a 120mm fan at one end for cooling. Also done low value 0.1% resistors: 121 x 12R1, 0.1% for 100 mOhm and 120 x 120R 0.1% for 1 Ohm calibration resistors at reasonable currents. Grant.
From: Hammy on 17 Jul 2010 20:39
On Sun, 18 Jul 2010 09:30:22 +1000, Grant <omg(a)grrr.id.au> wrote: [snip] >>The fun might come back when connecting the cold bulbs not two by two, >>but all at once. Tchk ... *POOF*. > >Decent converter should handle that? Not like 8:1 lamp hot:cold is >a short circuit, almost a short ;) It should be able to handle starting into a short. The inductor would saturate but the controller wont come on until on the caps charge up and it passes its UVLO anyway's. I measured the resistance from the fuse to the bridge rectifier its 4 ohms that includes a 5A, 2.5oHm NTC. So at the max current at worst case line peak would only be about 40A. That's well within the ratings of anything in the inrush currents path. You should test a supply into a short anyway's, this just saves me some time two birds with one stone.;-) >I keep an old fuser element in the cupboard for hi voltage loads, and >have light bulbs setup for 24V with 12V halogens in series, then proper >high wattage resistors picked up over time. > >Lamps are easiest to hook up, perhaps three or more in series at first? Yep that's what I'm going to do. Its the easiest and takes up the least room. I can just put the lamps down on the floor out of the way. >Over here they've banned incandescent lamps already, only those new and >expensive hi-voltage halogens available :( I suspect that will eventually start happening here as well. >What about an electric heater on low? Got a couple or more to wire >in series? Raid an electric stove, put elements in series? >> >> >>>> Good news is you may not even have to drive all the way to Home Depot. >>>> Supermarkets also have a variety of them. Of course, then your wife >>>> might hand you a lengthy "while you are there anyhow" list and you don't >>>> get to look at all the new power tools, barbecues and stuff. Man's toy >>>> store ... >>> We call that a honey do list here.;-) >>> >> >>Nah, a honey-do list isn't grocery shooping, it's when the missus wants >>you to get that tree stump out over yonder, and it's 105F :-) > >Grant. |