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How to Run a Cooler Regulator/Recifier?

in 912 / 914 Technical Questions 10 years ago
I want to minimize heat build-up in the regulator/rectifier on my 912ULS (RV-12). I have relocated the R/R to a cooler place on the airframe per Van's Aircraft's guidance.

Does it help to keep the R/R cooler if I minimize electrical loads during periods of low rpm operation? For example, should I not turn on strobes/lights/AP/etc until just before take-off?? Does operation at cruise (@ 5,250 rpm) with all of the electrical loads "On" cause the R/R to operate hotter? What is the R/R's heat signature a function of?

  • Re: How to Run a Cooler Regulator/Recifier?

    by » 10 years ago

    I was told that the regulator has to work hardest at low loads; the generator is always making as much as it can and the job of the regulator is to dump the excess.
      
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  • Re: How to Run a Cooler Regulator/Recifier?

    by » 10 years ago

    Good questions David. I too would like to know.....

    A cut and paste from this site states. http://pointsforpilots.blogspot.com.au/2012/12/testing-rotax-912914-generator-and.html
    15 - 20 VAC during idle
    30 - 40 VAC during high rpm

    At low RPM (taxiing) my regulator struggles to handle the load (output)with lights etc on.
    I wonder if the low input voltage, high output required plus lack of cooling air gets it quite hot?

    As you have stated, I now limit my electrical loads on the ground.
      
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  • Re: How to Run a Cooler Regulator/Recifier?

    by » 10 years ago

    I have been told by someone much more experienced than I in aviation electrics/electronics that the Rotax regulator is really a very poor device but it does the job. He told me that the generator/alternator produces a voltage (potential power) that increases with engine speed (see Rhett's post) and the regulator simply dumps any current that isn't used by the aircraft into a resistance that heats up. That is why there are cooling fins.

    If you're running the engine at high revs but have no (or very little) accessories (lamps radios etc) on, the regulator is generating a lot of current (amps) and the regulator is creating a lot of heat because of all that unused electrical power.
    If you're running at low revs (taxying) with the aircraft lit up like a Christmas tree and radios and transponders running then there is a good chance that the generator/alternator isn't supplying enough current and you start to drain the battery.

    On a small helicopter here in Europe with a 912S we started to burn out regulators and our first reaction was to switch off all the accessories. That didn't help and we realised that the engine was running constantly at 5500 rpm and often at 5800 on a hot day or with a heavy pilot and was therefore producing a lot more electrical power than we were using. The solution was to switch on all the lights and accessories so that we were using the power supplied by the generator rather than producing heat in the regulator. We later moved the regulator to a cooler spot but running the accessories certainly helped in the short term.
    Mike
      
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  • Re: How to Run a Cooler Regulator/Recifier?

    by » 10 years ago

    Sure is confusing! I would certainly like to hear something "official" from the ROTAX factory as to how we can best operate our electrical loads to reduce internal heat and therefore, hopefully, failures in our regulator/rectifiers (R/R). Should we run high electrical loads at high RPMs to reduce R/R heat? And low electrical loads at low RPMs to reduce battery drain and reduce R/R heat? We can cool our R/Rs all we want, but it sounds like internal heat remains high depending upon load. Where is some definitive ROTAX factory advice?
      
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  • Re: How to Run a Cooler Regulator/Recifier?

    by » 10 years ago

    before you try and figure out if your reg/rec is over heating I would apply a simple temp strip to it. I have them on my ignition modules and reg,rec. I have never seen over 145F on on the modules and 135F on the reg/rec. These strips are cheap enough and will tell you what your temps are on what ever part you attach it to. If you want to see what the temps are in taxi then go taxi for 20 min. If you want to see them in flight then go fly and these temp strips will tell you the info you need.
    These will tell you right away if you are having a temp issue on any given part.

    tempstrip.jpg (You do not have access to download this file.)

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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