[NSRCA-discussion] Electric Power Consumption

[George Miller]

Thanks, Steve- I picked the Actro 32-3 because I'm going to use one in my Ion and I therefore knew that it would run on the 5s4p packs.  I picked the prop at the upper end of the Hobby Lobby range...didn't do the RPM/volt calculation...but if that is true, even with only only one pack(5S), I'd be pushing 10K rev's ..... My Plettenberg turns about 9K with 42 Volts.  As to the cell count--- at 1.5 volt per cell, 26 nicad cells is about 39 volts...and since I knew the actro was run in heli's with the 10S setup, I thought that was pretty close.....

I'm not trying to be contentious, I'm just trying to learn how to do these calculations properly in the future.  Its all well and good to say use a proven system, but someone has to "prove" each one as they come available.   I guess I need much more info before I become a pioneer<G>.

G
  ----- Original Message ----- 
  From: Steven Maxwell 
  To: NSRCA Mailing List 
  Sent: Tuesday, January 10, 2006 11:22 PM
  Subject: RE: [NSRCA-discussion] Electric Power Consumption


   I'm trying to learn some of this also, so take anything I might say with a grain of salt, I will be using a standard setup this spring that many have already used.
   From Hobby-Lobby site for Actro 32-3
  For 14-26 cells in propeller models and 28-32 cells in helicopters. Propeller range is 13" to 18" in diameter. This 3 turn motor has an RPM/Volt of 555, resistance of 34 mOhm. Maximum efficiency of about 89% in the 50-95 amp draw range. Power output in the 550-2000 watt range.
   Sounds like you used 5S4P in series 42 volts X  RPM/Volt of 555=23,310 rpm.
    I tried to run a setup on motor calc but there data is so outa date nothing there to use maybe somehas elecalc to do figures for you.
   The other thing I have found on Hobby Lobby site is most of the time they talk about cells is to NiMh or NiCd if Lipo's they generally say so.
     Hope this will generate some info and the best of luck.
   Steve Maxwell

    ----- Original Message ----- 
    From: George Miller 
    To: discussion at nsrca.org
    Sent: 1/11/2006 1:32:01 AM 
    Subject: [NSRCA-discussion] Electric Power Consumption


    I have a problem with an electric conversion which while not precisely pattern related, I'm sure will be applicable to electric pattern problems...so I'll ask it here.

    I am trying to convert a Showtime from YS 110 4 cycle power to electric power.  After looking around the web, I got an Actro 32-3 - which is a popular motor for the Ion electric helicopter.  I know that this motor runs well with available ESC's on 5S4P lithium packs, so I set it up with a 17X12 APC e prop and a 77amp ESC from Hobby Lobby  ( esc and prop recommended on their website).    To make a long story short, the ESC litterally burned up 30 seconds into the first flight....but BOY WHAT POWER for that 30 seconds<G>!!!

    OK, so I'm thinking that burning up probably indicates a problem.....and I start to investigate...I hook up a watts-up to my Focus II with a Plettenberg 30-10 and a 21X12 APC and it pulls about 65 amps at full throttle on the bench....Then I set up the Showtime and it tops 75 amps at half throttle!! HMMM, so there is the problem....Now I try to make changes to decrease the amperage -- larger prop and smaller prop---no major change, then I tried just using a 5 cell pack cutting voltage in half...still about the same....so the question is:  How do you adjust the current drawn by an electric motor?  Can this set up be salvaged...Where did I go wrong and how can I avoid this in the future? 

    TIA for your help and the benefit of your experience!

    George


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