Products > Test Equipment
ARRAY electronic loads
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dolomike:
It would be more for analyzing performance of some of the power components and PCB in a design and not for testing closed loop control although there isn't much to the loop that would be affected anyway.

We do have switched resistance banks but would like to test with a constant current load ideally.

Mike
rx8pilot:

--- Quote from: nctnico on September 14, 2015, 04:20:26 pm ---I'm not quite sure a standard DC load will do what you want because the control loop will always lag behind and could mess with the control loop of the system you are testing. For this kind of tests I designed & build a switched resistor DC load myself. I can set it to a specific resistance and because its purely resistive it will keep that setting no matter what appears at the input.

--- End quote ---

That is what I did for my setup. Resistors and capacitors are dumb and predictable. I have an ARRAY DC load, but I am looking at a Chroma mainframe so that I can automate with LABView.





LabSpokane:

--- Quote from: dolomike on September 14, 2015, 03:38:54 pm ---Well, we normally run DC motors in automotive and heavy duty applications so this isn't a lightweight system. I think we would normally run CC or CR mode for most tests but some could be upwards of 800W. I believe this can be achieved by paralleling the devices in CC or CR mode. Some re-brands state they can be paralleled but I didn't recall seeing anything in the Array manual about it.

Voltage: 12V/24V nominal but some tests can be at 28V.
Current: ~10-15A but some tests may require almost 30A
Wattage: Most tests are done at 12V so we could do most of it with ~400W but if the parallel combos work, then we can get up to the ~850W for the extreme tests.
PWM Frequency: 5kHz-20kHz
Filtering: What type of filtering are you asking about?

I guess a lot depends on the current slew rate but the manual states 1mA/us~4A/us on CCH mode which is quite a range so not sure what the driving factor will be.

The transient generator can handle up to 50kHz so I would expect it could handle a PWM source upwards of that frequency as well.

Thanks for the feedback.

Mike

--- End quote ---

Could you or someone else explain how a constant resistance / current can simulate a motor load?  Not that a electronic load could do much better of a job, but unless you get some sort of a custom wind, typically a power resistor is wound to be non-inductive.
dolomike:
We've looked at the Chroma stuff as well but I don't want to spend over $10k for a 1200W system and probably not use half the features. We aren't looking for pinpoint accuracy since we are using 10's of amps and not worried about mA resolution/accuracy.

To help simulate a motor, you do have to add in a comparable inductance. Although you won't ever get the same behaviour as a motor at least you can get it close enough to validate some aspects of the design. The nice thing about the DC load is the transient generator which could help with ripple testing to a certain extent.

Another way we have done it is to drive a motor coupled to another and connect that to a load bank.

I'd like to have some finer grained control over the load that a switched resistor bank can't easily do especially when operating at varying voltages.

Mike
nctnico:

--- Quote from: rx8pilot on September 14, 2015, 08:52:05 pm ---
--- Quote from: nctnico on September 14, 2015, 04:20:26 pm ---I'm not quite sure a standard DC load will do what you want because the control loop will always lag behind and could mess with the control loop of the system you are testing. For this kind of tests I designed & build a switched resistor DC load myself. I can set it to a specific resistance and because its purely resistive it will keep that setting no matter what appears at the input.

--- End quote ---

That is what I did for my setup. Resistors and capacitors are dumb and predictable. I have an ARRAY DC load, but I am looking at a Chroma mainframe so that I can automate with LABView.



--- End quote ---
That is rather crude. I came up with this (neatly controlled with a microcontroller):
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