PDM load limit and expected behaviour

[phatbob]

Hi

we have a unit on a rally car that could be 'close' to maxing out the rated output, if it were to be a rainstorm, in the night, with heat required to cool the car, demist required to defog the screen, and all the fans going. its a stretch, but in any case, what is the expected behaviour when the total amps exceeds the 'rated' amps (90 something on a PDM 30).

can we ever define a 'priority' order where some outputs take priority over others (or a shutdown priority such that for example rad fan will always work but perhaps corner pod lights might get sacrificed). I know the better answer is to run 2 PDMs but its kind of a boundary case, just wanted to cover it.

Thanks

[JamieA]

Ok, the answer here isnt too specific.

We have tested the unit to those limits (100a on a PDM30) and that is where we set the recommendations.

We havent tested a unit to destruction to find out what happens when you go above that.

One known thing is that you need to keep the internal temp below 110c, so make sure that you log and perhaps alarm that channel on your dash to know when you are getting to the temp limits of the device.

It is highly recommended that the PDM is installed in a way to keep it as cool as possible, as the cooler the PDM is, the more current it will be able to deal with, but there will still be a limit regardless of how cool the unit overall is kept.

I would suggest that you look at your total loadings and work out how you would like to distribute your 100amps. Then set your individual channel limits so that the combination of them all keeps the unit below the threshold. If you want certain things to turn off first, then you can set their threshold lower than others.

You might find that the current loadings when everything arent quite as high as you think, I have found that with my race car. It is worth wiring the car up, and turning on each item, to see what current it really draws. Ususlly they are lower than you think. then you can set limits on each item, with the knowledge of what it usually does..

regards,

Jamie