adding load

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eplmisme

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bellevue wa
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signal electrical inspector
i am a signal electrician for a municipality. we are testing a new UPS system on our in house "bench" signal cabinet. in house we do not have enough load to represent our largest loads in the field. the cabinets draw around 2.5 amp at 120vac. i want to add 1.5 amps to our bench test. i was thinking the easiest way would be to add a 180ohm resistor in series to create an extra 1.5 amps. my question is would this be something that could damage the electronic components in the cabinet: controller, MMU, power supplies, ...?

plugging a load into the power strip inside the cabinet would be creating a parallel load and would not give the desired effect.

i know on DC circuits you can make a continuous current load with a mosfet and some other components. these are from what i can see only for lower voltage DC circuits.

any help would be great.

have a great day.
evan
 
Don't forget about the power being dissipated by that resistor. I^2R says 405 watts is being dissipated by that resistor, so you need a hefty one. Also do you need 180 ohms or 80 ohms? Maybe I don't understand your circuit, but how does adding a resistor in series increase the load on the circuit? Would expect it to decrease whereas a parallel load would increase the current being drawn.

It sounds like what you need is a load bank for 120V. A bunch of parallel incandescent lamps is effectively the same thing if you can still buy any of those.
 
One reason mentioned the lamps was due to he wanted to be closer to a field install which will have this current draw. This will impact the performance of the ups.

I think that would be a more accurate test.

Maybe we should ask what the field load conditions are. Then design the test circuit.
 
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