From: BobEngelhardt@comcast.net   
      
   On 1/6/2021 2:53 PM, Phil Allison wrote:   
   >   Bob Engelhardt wrote:   
   [snip]   
   >> I long ago lost any ability to do the Fourier calculation, but somewhere   
   >> on the web (source lost), I found that the DC component (a0) is 88% of   
   >> the RMS AC input to the bridge. [snip]   
      
   > ** DC motor speed *approximately* follows the average value of the input   
   voltage, not the RMS.   
   >   
   > For 20VAC, this is 0.637 times the peak or 18.0V minus diode losses, so   
   about 16.5V   
   >   
   > I suspect your test is flawed.   
      
   We're actually saying the same thing: my 88% of RMS is .88 x .707 x peak   
   which is 0.622 of peak (OK, it would be 90% of RMS to be 0.637).   
      
   And "average value" is just what the DC component of the Fourier series is.   
      
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