Need help drawing a big load!

Thread Starter

Pidgeydoyle

Joined Dec 4, 2012
17
Hey everyone,
I need to develop a test rig of some sort that would draw a 3-phase load at 230V 32A per phase, (22kw overall) and dissipate it somehow...

Currently im thinking of putting multiple high power resistors on each phase in parallel and allowing the energy dissipate as heat (with plenty of assistance) but its working out pretty expensive!

another option would be to take domestic heating elements and have a similar set up.

anybody got any thoughts of recommendations in relation to this?
 

paulktreg

Joined Jun 2, 2008
804
I think I'd be looking at heater elements. Another option is electric kettle elements providing you can safely get the necessary water supply because I think they'd have to have flowing water to keep them cool if running for prolonged periods. (You can get 2.5kW elements for as little as £10.00 in the UK).
 

wayneh

Joined Sep 9, 2010
17,155
I'm always a fan of lightbulbs for dummy loads. They're cheap(ish), easy to find and replace, give a visual indication, and are purpose built to dissipate the heat they make. Maybe something like this.

You could use all the light to set up a wicked hydroponic farm! :p
 

#12

Joined Nov 30, 2010
18,223
5KW, 230V, nichrome heaters cost $50 a pair, wholesale. They will survive with about 600 cfm of air being jammed through them with a squirrel cage fan. In America, we call them, "furnaces". (It's my day job.)

So, here's a drawing of what I can do when stuck with 5KW units while trying to avoid fixing a car before sunset in Florida. (A heat index of 86 F at night is so much better than a heat index of 96 in the daytime.) The load isn't balanced, but I need to kill a couple of hours. I expect you know the formula for heating water is 1 B.T.U per pound-degree F and a watt-hour produces 3.413 B.T.U.s. The formula for burning air is: B.T.U = 1.08 CFM dt (in F again).

Just an idea, and some math to keep you from melting steel.
 

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Thread Starter

Pidgeydoyle

Joined Dec 4, 2012
17
Thanks for all the suggestions guys!

To be honest id rather stay away from anything water cooled for safety and portability reasons. I really like the idea of the bulbs - cheap, easy to identify faults and it would make me look like a mad scientist when powering it up! not to mention the herbs that could be cultivated!
 

Ron H

Joined Apr 14, 2005
7,014
Thanks for all the suggestions guys!

To be honest id rather stay away from anything water cooled for safety and portability reasons. I really like the idea of the bulbs - cheap, easy to identify faults and it would make me look like a mad scientist when powering it up! not to mention the herbs that could be cultivated!
What is your definition of cheap, as regards this project?
 

crutschow

Joined Mar 14, 2008
28,201
Thanks for all the suggestions guys!

To be honest id rather stay away from anything water cooled for safety and portability reasons. I really like the idea of the bulbs - cheap, easy to identify faults and it would make me look like a mad scientist when powering it up! not to mention the herbs that could be cultivated!
You do realize that a 22kW lamp generates a heck of a bright light. :rolleyes:
 

tignmeg

Joined Oct 17, 2012
4
You could use a 22kw 3 phase motor for that job. And if you wanted to control the power dissipated add a variable speed drive.
Of course this would be significantly more expensive than the other options mentioned so far but possibly more elegant.
 

Thread Starter

Pidgeydoyle

Joined Dec 4, 2012
17
What is your definition of cheap, as regards this project?
As cheaply as possible tbh but definitely In the <€500 range...

You do realize that a 22kW lamp generates a heck of a bright light. :rolleyes:
not too worried about that - the workshop is pretty dark!

You could use a 22kw 3 phase motor for that job. And if you wanted to control the power dissipated add a variable speed drive.
Of course this would be significantly more expensive than the other options mentioned so far but possibly more elegant.
Yes i had considered this a little bit, the only downside would be cost and noise. also i'd have to create a very strong mount to stop it hopping all over the place!!
 

richard.cs

Joined Mar 3, 2012
162
You really should look at water cooled, it's a lot of power to try and dissipate any other way. Three ordinary electric showers, one per phase will do the job cheaply and safely. Or if you don't have sufficient water flow then you're looking at something more like an industrial immersion heater (or many domestic ones) in an 44 gallon drum full of water.
 

#12

Joined Nov 30, 2010
18,223
You really should look at water cooled, it's a lot of power to try and dissipate any other way. Three ordinary electric showers, one per phase will do the job cheaply and safely. Or if you don't have sufficient water flow then you're looking at something more like an industrial immersion heater (or many domestic ones) in an 44 gallon drum full of water.
It depends on what's convenient. A squirrel cage fan out of an old air conditioner is available to me, but 3 showers worth of plumbing? That needs stuff I don't have in my junk pile.

Now, about those 44 gallon barrels. In the U.S. we have 55 gallon barrels. Is this why a pint of stout seems so small?:rolleyes:

and a thanks to Pidgey for the LOL!
 

richard.cs

Joined Mar 3, 2012
162
Yes they're the same barrels, the gallons are a different size (and yes I know how crazy it is :D ).

To keep the temperature rise reasonable with 22 kW (how hot can your elements safely get?) with air cooled will need a lot of air, probably more than you'll get from that blower. Once you know what the acceptable temperature is you can work backwards to the flow rate.

A barrel full of heaters on the other hand can just be left to boil, the latent heat of evaporation is huge for water. And it's simpler than plumbing in showers.
 
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