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    Keppe motor V3.0


    j greef

    Posts : 36
    Join date : 2008-12-31
    Location : Europe

    Keppe motor V3.0

    Post  j greef on Mon Mar 21, 2011 4:21 pm


    Please find enclosed my first test results with a simplified Keppe V3.0 motor.

    The simplifications are as follows:
    * Use of reed switches instead of opto coupler circuits.
    * One pulse per cycle instead of 2.

    My motor has already run with two pulses per cycle but I have some tuning problems in that case.

    Results (see also pictures below):

    Input voltage for motor circuit: 10,8 V
    * The motor drove a 4 blade diameter 20 cm ventilator at 914 rpm (65,6 msec/cycle).
    * Amplitude of AC voltage: +/- 10.6 V
    * Calculated average value of +/- 7 V (rms value of 4,79 as on the picture seems incorrect)
    * Current (motor circuit): between 40 and 60 mA (see picture + extra check with analog Amp meter).

    Calculated results:
    Absorbed power by motor main circuit: P = U x I = 7 V x 60 mA = 0.42 W (conservative guess)

    * Measuring method: amps are visualised on the oscilloscope by measuring the voltage drop over a 0,15 Ohm power resistor. A probe correction was set so that the displayed mV readings correspond to mA values.
    * As I have serious doubts about the accuracy of my Amp meter and the rms readings the oscilloscope provides, the calculated power values should be considered as “order of magnitude” only.

    Motor efficiency = ?
    * During another run, the motor was able to lift a 31 gr load over 75 cm in some 1,9 seconds. The average power then is 0.031 x 9.81 x 0.75 / 1,9 = 0.12 W.
    * The absorbed power was estimated at 0.62 W for the main circuit so the efficiency then was 0.16 / 0.62 = 19.3 %
    * A quick measurement of the secondary circuit showed that it consumes some 35 mA @ 10,5 V = 0.37 W. If you add that to the 0.62 W of the main circuit you get a total of 0.99 W. In that case, the overall efficiency drops to 0.12 / 0.99 = 12.1 %.

    Attachments: oscilloscope pictures (sorry for the quality, I have no screen capture tools on that oscilloscope):

    Current (CH2) and voltage (CH1)

    Current only (CH2)

      Current date/time is Tue Jul 25, 2017 12:38 am