How to make a high watt load? - Page 1
Forum section: electronics / beginners

author: Hex173t
author_rank: Contributor
timestamp: December 01, 2013, 11:45:23 am
content: Hi allI was reading another thread (https://www.eevblog.com/forum/beginners/determine-transformer-amps/) that said to load down a transformer to determine its amp capacity. Using my limited knowledge and imagination, I would use many of the various resistors I have that range from a few 10w low resistance ones to a bunch of 1/2w ones. Maybe even use some motors. Is this how it's done by you experienced people? I'm sure there's a more elegant way than I can think of with limited parts.Thx

author: Jon86
author_rank: Frequent Contributor
timestamp: December 01, 2013, 11:51:53 am
content: I think you'd be better using the other method of weighing it and calculating it that way. Or maybe if you know what device it's from, you can use that to help you.Just remember that you're getting AC, using a motor isn't going to give you a very accurate results.Power resistors are pretty cheap anyway, just go out and buy a load of 5Ws and give it a shot.

author: monpjc
author_rank: Contributor
timestamp: December 01, 2013, 07:40:14 pm
content: If your talking Watts, not Kilo Watts then trip to local auto shop for some 12v brake lamps or hardware store to find some 100Watt light blubs. Nice linear load for AC circuits. I used to test a 250Watt power supply I helped develop with bank of light blubs)

author: tesla500
author_rank: Regular Contributor
timestamp: December 01, 2013, 09:27:58 pm
content: If you're really cheap, a bucket of water an bailing wire makes a nice multi-kilowatt load. Literally.Did you know bailing wire is about 1Ohm per meter, and can handle a loading of at least 10W/cm when submerged in water?https://twitter.com/tesla5hundred/status/405567197717594112

author: Dave Turner
author_rank: Frequent Contributor
timestamp: December 02, 2013, 11:43:14 pm
content: I remember doing experiments in the late 60's early 70's using oil as the cooling medium. Standard mercury thermometer, 11kV supply, Hammer house of Horror knife switches, on a 150mm thick isolation pad to check the heating effects etc.

author: Rigby
author_rank: Super Contributor
timestamp: December 03, 2013, 12:45:00 am
content: Quote from: tesla500 on December 01, 2013, 09:27:58 pmThat is impressive, somehow.

author: oldway
author_rank: Super Contributor
timestamp: December 06, 2013, 03:36:42 pm
content: I use cheap MIG weld inox wire 0.8mm 308L.It has a cold resistance of more of less 1.8 ohm/m and can be used up to 7 A in free air.The wire is twisted and silver brazed at both ends for low temperature connections.

author: owiecc
author_rank: Frequent Contributor
timestamp: December 06, 2013, 08:29:45 pm
content: In our drives lab we used barrels of water with a bit of dishwashing liquid to make it conductive. It looked like soup after some time.

author: Rigby
author_rank: Super Contributor
timestamp: December 06, 2013, 08:59:23 pm
content: Quote from: owiecc on December 06, 2013, 08:29:45 pmYeah, the electricity will separate the water into hydrogen and oxygen, and the soap will do what soap does and create its own bubbles.It seems to me like distilled water with some salt added could be a reliable load if you let the hydrogen and oxygen escape.

author: Hex173t
author_rank: Contributor
timestamp: December 06, 2013, 11:31:07 pm
content: I really appreciate the ideas you fella's have suggested. When I posted the question, I really was thinking of a bunch of 1/2 watt resistors in my bread board. I am fully guilty of not thinking of what I have in my garage. I have plenty of stainless, brass and copper safety wire and bailing wire but it just didn't enter my thought.Thanks again.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: December 07, 2013, 01:40:47 am
content: Quote from: Rigby on December 06, 2013, 08:59:23 pmExcept for with salt you will create chlorine gas. In small amounts this would be negligible but in some situations could pose a health hazard.Sent from my EVO using Tapatalk

author: owiecc
author_rank: Frequent Contributor
timestamp: December 07, 2013, 10:02:44 am
content: Quote from: Rigby on December 06, 2013, 08:59:23 pmThat was an AC load for loading induction motors.

author: Laurynas
author_rank: Contributor
timestamp: December 09, 2013, 05:39:48 pm
content: I'm using 500W halogen tube.just have to keep in mind that resistance is much lower while it's cold.

author: edpalmer42
author_rank: Super Contributor
timestamp: December 09, 2013, 06:34:04 pm
content: If you have a variac you can use it with an ordinary electric heater to get a variable AC load that's suitable for relatively large loads. Connect the heater to the output of the variac and set the voltage to zero. Connect the input of the variac to the transformer under test and gradually increase the voltage. This will increase the load as seen by the unit under test. If the output voltage of the transformer is low, you might not get enough current flow. In that case, you could use a transformer to better match the output voltage of the transformer to the input voltage rating of the variac. Be sure to stay within the voltage and current limits of all the pieces.Ed

author: electronics man
author_rank: Frequent Contributor
timestamp: December 11, 2013, 09:21:59 pm
content: why dont you buy a 100W power resistor you will have to calculate the value by usin the equation p = V^2/R or find curent using I = P/V then R=V/I

author: electronics man
author_rank: Frequent Contributor
timestamp: December 12, 2013, 07:54:04 pm
content: any way what sort of power are do u think you might need

author: N2IXK
author_rank: Frequent Contributor
timestamp: December 12, 2013, 08:14:13 pm
content: Quote from: PedroDaGr8 on December 07, 2013, 01:40:47 amIn addition to the chlorine gas, you will also create sodium hydroxide (AKA lye or caustic soda), which goes into solution and starts to corrode your electrodes....