AC three phase load bank

[olicg]

I need to design a three phase AC resistive load bank for diesel generator load testing. I dont have time or budget to go for buying a load bank. A temporary made bank would serve the purpose. I was wondering what loads to use, what type of cooling to provide, etc.

Can someone refer me any literature available on the net? I want to make a 200 KW with 10 KW steps at 415 V voltage.

I know it is a little question put to big experts but any help will reduce my burden.
Thanks,
G. Olic

 

[ccjersey]

I've never done it, but have heard about using a tank with water and electrolyte (salt) to immerse three electrodes connected to the three phase conductors. Load is adjusted by electrolyte strength and ultimately by the depth of immersion of the three electrodes into the electrolyte.

The electrolyte may boil (and gain strength by dissolving more salt), so a heat resistant tank is necessary. Guess if would depend on the size of the tank vs the KW absorbed into the electrolyte. Perhaps someone will know what sizes you would need.

Other than that, salvage heating elements from direct electric heating or auxillary heat on heat pumps could be banked together if you could find compatable voltage equipment. Most I have seen are in 5 kW units.

 

[alehman]

Have you considered renting one?

http://www.loadbanks.com/

 

[CJCPE]

200 KW is a lot of heat to dissipate. If you could use a motor load, you could couple two motors together and use a regenerative drive (either AC or DC) to put power back on the power line.

If you must have a resistive load, water cooling might be necessary. You might be able to use some water heaters.

Space heating equipment as suggested by ccjersey could be used, but you would need a lot of big fans to move the heat away.

If you want each step to be 10 KW total, 3.3 KW per phase, there is a good chance that you can find individual loads that can be connected in series to get the required resistance values.

 

[davidbeach]

A rental load bank, located out doors, seems to be the best solution. Any generator vendor or testing agency ought to be able to supply a load bank that small.

 

[cuky2000]

What about paralleling with the utility or local load?

 

[waross]

I had to load up a 275 KW diesel set for a week to satisfy a vendors requirment.
I used six plastic 50 gallon barrels, two per phase. I found 12 leaf springs from a truck suspension system. I located the whole thing up on a roof for safety, and easy access to the power cables. I dropped two spring lea\ves connected to different phases in each barrel. Filled the barrels with water and threw in some salt. It worked. We ran it for about a week.
The water boiled. I was on site 4 to six times a day adding water. When I arrived each morning, the barrels would be about 1/3 full. It was a load, but it was not particularly controlable.
Years ago we were looking at some bid documents form the supply and installation of a generator. One requirement was a load test after the installation was complete.
The generator vendor said
"No problem", and described the following scheme.
Rent a trash container for a week. The size that is picked up by a truck rather than being just dumped into a truck. About 20 cubic yards or more. Seal the doors with silicon and fill it with water. The greater volume of water reduces the evaporation problem. Control is done by raising or lowering the electrodes.

Paralleling with the utility is great from the generators point of view.
Look in some old books for the connections for the synchroizing lamps.
It may be hard to get permission from the utility, and there are safety issues with backfeeds if there is a mains failure while you are online.
If you are able to connect to the mains be aware of the following.
1> The load will be determined by the govenor setting on the diesel. Control the load by increasing the speed setting slightly on the governor. If you have an electronic governor, use the "Droop" mode.
2> The voltage setting will control the power factor. It is possible to run full load current through the generator at almost 0 power factor with the voltage set too high. The engine will be doing alsmost no work.
3> If you inadvertantly turn the governor setting the wrong way, the generator will start to run as a motor and drive the engine.
I would have no hesitation to using the power lines for loading IF I COULD GET PERMISSION FROM THE POWER UTILITY.
In North America I doubt that I could get permission.
South of the border, I know one utility who would give me permission, and one other utility who might give permission.