Loading up a 36kW transformer

rent a load bank from a generator rental/testing company.

Den mandag den 7. oktober 2013 17.22.29 UTC+2 skrev Yzordderrex:

un. I looked at having some inductors wound, but that was about $4k. I've looked at custom load bank, also about $4k. I can run three electric wate r heaters ($250.00 each)and discharge about 90 gals an hour of hot water. The eagle glo-coils are not manufactured anymore - what a shame. I've look ed at immersion heaters and also stuffing a 50 gallon drum with elements fr om a stove.

7kW and make up the rest with some big wirewounds I have kicking around. bu t looking for any alternate methods before I go to boss with the water heat er idea.

a few of something like this?

-Lasse

I like the idea of buying three water heaters and doing a little plumbing. Spend about $1200 and at the end of the job sell them for $250 and it only cost you $450. You might want to get 4 water heaters, reduce the amount of wire wounds heating the room. I would put a valve on the input of each so you can equalize the water flow, just to make sure one doesn't get starved. Mikek

This probably won't work because of asymmetrical cooling, and would only work if they have adjustable taps.

But:

You could hook up two, back to back, with taps set for different ratios. (or if you have an existing product, particularly bigger, use that). Verify that everything is phased correctly so that with the taps set at the _same_ ratio the outputs are the same (unless you like very large and spectacular career-changing events). The change the taps, and connect like outputs to like through small* resistors.

Most of the 36kW (or whatever) flowing through the transformer will just get put back on the line, with only enough dissipated in the resistors to keep control of things, plus losses in the two transformers.

• "Small" is a relative term when you're talking 36kW -- you'll need to do the math, but I suspect you'll be looking at no more than one or two kW each. If you can arrange your taps so that the difference between the outputs is 12V or 24V, then banks of automobile headlights would work, and would provide an easy way to switch load in and out. They'd also significantly reduce the drama if you do get the phasing wrong.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com

With the secondary O/C, measure the temperature rise due to iron losses with full primary volts and no secondary load

Then short the secondary and apply reduced primary volts from another transformer to measure the temperature rise due to copper losses at full current.

Then calculate the effect of both together.

--
~ Adrian Tuddenham ~ 
(Remove the ".invalid"s and add ".co.uk" to reply) 
www.poppyrecords.co.uk

So far I like the electric water heaters the best. I can load to about 27kW and make up the rest with some big wirewounds I have kicking around. but looking for any alternate methods before I go to boss with the water heater idea.

Any ideas?

Bob

********************* Clothes dryer elements are 240V and air cooled which may be less work than plumbing the water heaters. They're certainly less expensive. Art

So far I like the electric water heaters the best. I can load to about 27kW and make up the rest with some big wirewounds I have kicking around. but looking for any alternate methods before I go to boss with the water heater idea.

Any ideas?

Bob

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How about using one 55 gal drum (open) with several 4.5 kW water heater elements installed near the bottom. Just let it boil off the water and add more if necessary. You could wrap insulation around it for safety and pipe the steam outside.

tm

So far I like the electric water heaters the best. I can load to about 27kW and make up the rest with some big wirewounds I have kicking around. but looking for any alternate methods before I go to boss with the water heater idea.

Any ideas?

Bob

++++++++++++++++++++++++++++++++++++++

Another way would be to use a duct heater and fan assembly. I thing any HVAC supplier can supply what you need. I think they come in 15 kW steps.

Too bad about the Eagle heaters, have used them in the past.

Toaster oven elements? Electric stove elements?

I hate water and loads, but have seen water loads used. The water heater may work as long as the thermal energy is extracted from the tank. Which brings up the thought of on-demand heaters. (might be what your thinking)

Cheers

If you luck out you may be able to find some 240V/10A stadium lamps on an auction site. From a closed-down stadium they are often sold in bulk for cheap.

Then you could really light up the place.

--
Regards, Joerg 

http://www.analogconsultants.com/

Nichrome heating coil wire (.25in ID preformed) is also available at about $6 a foot. Should be > double original length for heat transfer. Coming up with a safe form that doesn't bankrupt you for ceramic insulators will take some thought.

RL

Hire a lighting tower or similar load from a hire / rental company??

"Adrian Tuddenham"

** Cleary the smart way to do it - the temp rise in both cases should be nearly the same.

The way to measure it is to note the fractional rise in primary resistance and use the tempco of copper.

IOW: Internal temp rise = 256 times the fractional increase in primary R.

However, temp rise and power loss are not linearly related - the combined effect will raise the temp less than the sum of the two rises.

... Phil

The water heaters are not a bad idea. You could do the same thing in a much smaller space by skipping the big storage tanks and installing water heater elements in pipe sections with tees on the ends, arranged to self vent with a 90 GPH flow switch and contactor for low flow protection. 3 smaller elements on a 3-phase variac could be used for trim, and the whole thing could be stuffed under a bench or on a shelf when done in case you need it again.

Depending on where you are located you can rent a load bank for about $700/week. That was for a Houston,TX location. If you are going to be running test over the next year or so then think about buying a used one, then sell it when you are done.

Google will give you lots of hits with "load bank rental"

--
Chisolm 
Republic of Texas

Even better! It provides some safety margin. I like it.

John S

So far I like the electric water heaters the best. I can load to about 27kW and make up the rest with some big wirewounds I have kicking around. but looking for any alternate methods before I go to boss with the water heater idea.

Any ideas?

Bob

Well & truly in the 'don't try this at home' category, generators in remote areas were, and maybe are, tested by filling a 44 gallon drum with water, and immersing 3 metal plates connected to the phases mounted on a wooden support. Power up, then add salt to the water to get the required load.

My electric kitchen stove says it is 11.8 kW at full load. As a bonus, you wouldn't have to do any plumbing. Hit up the used appliance store?

Every HVAC shop will have some used electric furnaces kicking around. If you swear that you aren't going to install it in a house again, they might sell one to you for cheap. You do probably need to hook up the blower motor so the elements don't melt. It will also probably have time delay relays on some of the elements so the whole thing won't come on at once; this may or may not be what you want.

If you have way more time than money, hit up the local junkyard and get every sealed-beam headlight you can. The high beams are usually about

65 W, so a string of 20 gets you a whopping 1.3 kW. (Tip: Don't try to wire it so both the high beam and low beam are on; this will burn out the lamp very quickly. I found this out when building a load bank this way for a much smaller DC supply.) On the other hand, this gives you control in 1.3 kW increments. :)

Matt Roberds

water can absorb a lot more energy if you discharge it as steam.

--
?? 100% natural 

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