What is filtered DC current

[Toytaco2]

The installation instructions for my Fantastic Vent state "Permanent magnet motors perform as designed on filtered DC current. Unfiltered DC current may create irritating noise from fan blade motors".

Electrics are my weakest area of knowledge and I've been reading numerous threads concerning battery chargers, wiring schematics, etc. No where do I remember "filtered DC current" being discussed. Can someone explain what this is about and what I need to do to install the fan to avoid that "irritating noise" (I plan to have several 110 plugs, battery and charger, and all 12 volt lighting plus the Fantastic Vent - simple as possible)?

[Dale M.]

Generally (for this application) it would be a large capacitor across the power supply leads.... But this is only relevant if you are on a converter that has a "high ripple output" at dc voltage level.... IF you are on battery power or have battery in system while running a converter, it should be "clean" enough to not cause a problem. A battery full time in dc circuit is a really really good "ripple" filter....

Dale

[jss06]

When you convert AC to DC you get a small fluctuation in voltage. The filter (capacitor or battery) fills in the dips to even out the voltage.

In a worst case senario you my hear the fan speeding up and slowing down constantly. But as stated above a permanent battery makes a good filter.

[Dale M.]

Most "ripple" is at 60 hz (60cycles a second ) or 3600 cycles a minute... Its NOT going to effect motor speed in any way you can tell... Other than manufacturers "claim" of weird noises, which is questionable... Unless you are looking at supply line with test gear, meaning a oscilloscope, you will never know if "condition" (ripple) even exists.

Dale

[jss06]

Most "ripple" is at 60 hz (60cycles a second ) or 3600 cycles a minute... Its NOT going to effect motor speed in any way you can tell... Other than manufacturers "claim" of weird noises, which is questionable... Unless you are looking at supply line with test gear, meaning a oscilloscope, you will never know if "condition" (ripple) even exists.

Dale

But if your converter is bad enough and you have a fluxuation of say between 12 and 14 votls that will cause odd things to happen and you may see the speed fluctuation i mentioned above.

* removed as it was argumentative and not conductive to the converstaion *

[Toytaco2]

I will definitely have a battery in the system full time. I will either be running from the battery only, or, if shore power is available, I will have a smart charger (Deltran or CTEK) connected while simultaneously using the few 12 volt accessories (several lights and the Fantastic Vent fan). It sounds like we are saying that since I am using a battery in the system I probably do not need to worry about the "noise factor" in the fan motor. Thanks for the help.