Anyone using a DC Load?

Setting up for a distorted voltage test, need to have a variable resistor to dial in the THD. the resistor is on the rectified side of a bridge so seeing only DC. but the power dissipated is on the order of 6.5kW... accounting for derating I need around 10kW or more for this load.. I have seen a few electronic loads.

Also, rectifying 230Vac l-n so Voltage into load is around 400Vdc so 500V range is necessary.

Good Experiences? bad experiences?

The very common and inexpensive Ohmite 225 W resistors (see Digikey) work well especially with some forced air for this sort of load.

At 6.5 kW and allowing for a 50 degree C rise in the air it will need 260 cfm of air on 30 resistors. For a simple test load I do not derate the resistors

Digikey also stocks the 2500 watt TE Connectivity resistors. You will need only three and at $80 you have an inexpensive load. These work well and look impressive.

For this range of power, I have found that using a commercial (HVAC) duct heater works well. They are available in many sizes, so you will have a wide choice to select the best one for your app. Although configured for 3P, they can easily be rewired for DC (1P) application. Use standard fans for helping heat dissipation, and as always, be sure to configure for electrical and thermal safety.

Digikey has the Huntington FSE1000-1.0 resistors in stock. These are 1 ohm, 1000 watts and $42 each.

those are all great ideas - I have used resistor load banks as well as light bulbs (watch out for the inrush currents) also you can screw in heating elements in place of the light bulbs in the ceramic sockets you can buy from home depot or lowes. if you need an active electronic load for AC that you can adjust PF and phase angle loads for various reactive conditions Chroma and california instruments makes them I cannot remember how much power they offer -but be prepared to spend some money for these. We used them for UPS - Inverter and motor drive testing in one of my prior assignments.

at one ohm and needing to achieve a load of 50ohms plus some flexibility I would need... well 50 of those.. so 2,000 dollars there.. plus switches contactors etc... labor to build, a cabinet to put in, thermal fuses safety and fans. after all that is said and done, I would be nearing the 30,000 dollar price tag of the electric load I was eyeballing (We would rent and thus not spend 30k)

This intrigues me, as the device is actually a 3ph device, however the test required is a voltage distortion onto each input phase, but having a 3ph load around also helps our cause in buying/renting something suitable. plus its getting to be winter in the midwest hah

The full setup looks something like this..

California Instruments MX30 power supply to our device to a lightbulb and resistive load (we are using the lightbulb and ceramic sockets as loads for low inductance starting) now I need to parallel in this new load for a qualification test. the actual EUT is 3phs 8700kVA device so having dual use for the load would be nice. we know it can drive a bridge to a DC load if necessary too.

OK - that makes sense now. I saw the title of DC load then saw all the reference to AC specs - THD etc.. i have also used Amrel DC loads I do not believe they make AC loads that may work for you if you can do the bridge in front of it.
best of luck

Along these lines, Hotwatt in Danvers MA makes finned strip heaters in the KW range. They are designed for 120 or 240V at various power ratings. Convenient to apply, all they need is lots of forced air. Reasonable prices too.

I have used them only as heaters running off AC so can't speak for their resistance stability, inductance, etc.

http://www.hotwatt.com/finned.htm

Just a reflektion. How would a common water boiler work? cheap and you might get refreshments at the same time. You might be needing a couple but the price is right....
And reuseable.

WATLOW makes air cooled and water cooled loads.