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Rotax SI-PAC-019 Optional Heat Sink indicates that the voltage regulator B is prone to overheating but they don't say why.

The Airplane Factory (Sling) and Vans (RV12is) say that it is because of light electrical loads.

Although there is a ton of info out there about overheating regulators on the 912 ULS, there is hardly anything about the 912iS regulators.

Do any of you have any knowledge or experience with this issue?  Thanks

8513_1_SI-PAC-019_Optional Heat Sink Set for VR B Nov 2019.pdf (You do not have access to download this file.)
8513_1_sling.png (You do not have access to download this file.)
8513_1_VR info .jpg (You do not have access to download this file.)
  • Re: Overheating voltage regulator B

    by » one month ago


    The iS engines have a 600W stator (3 phase generator) mounted to the end of the crankshaft.  The stator itself is split into 2 parts, 200 W for the primary functions like 1 injector set and 1 spark plug set, the fuel pumps, and a few other things.  There is not much electrical load, it looks after the main parts that keep the engine running.  The big part of the stator, some 400 W, also handles 1 injector set and 1 set of spark plugs with that it has a massive amount of energy to charge all the battery, run all your electrical needs with a lot to spare.  (approximately 30 amps worth) Here is where it gets interesting.  The A regulator, the one that the 200 W is connected to, is well balanced and the regulator has no issue to handle this power.  The B side however runs into some huge issues as it carries the big loads and when you do not consume them it has to do something with that energy.  We need to note that these are what are called shunt regulators, which means all the energy that is not used must flow into the ground.  If we have too much energy flowing, if it has little to no cooling air on the wires and the ground plate that the regulator mounts on...well things can get toasty, they fry, the burn, they can fail.  Sling and Vans have it right, if you have a very light load on the system you have to address the heat of current flow to the ground, this is where the optional heat sink can really help you.  

    You can check out how these work in some other publications.  Check the net, this is a common issue in motorcycles with the same type of electrical systems.  In some aircraft the fuse boxes are tucked away with almost zero air flow, the results are not happy ones in that you may have failures due to the lack of cooling of the regulators. The A, don’t worry about it.  The B one, yup, that one can fail if you do not address the energy flow.

     

    Cheers

     

     


    Thank you said by: Jon Tensfeldt

  • Re: Overheating voltage regulator B

    by » one month ago


    just a note that I should have made clear.  The fuse box is what shuffels the power.  It is the computor that runs the injectors and sparks, it splits this up so one side only handles 1 set of each for reducndnecy.  The power from the stator split is due to the fact that the A side computor and related bits it controls draw a lot less thant the B side (the 400 watt side) All the battery charging, and draws you put on the aircraft, will be from  that path.  

    Cheers

     

     


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