Re: [TCML] Two phenomena...

[EVP <evp@xxxxxxxxxxx>]

Phil Tuck wrote:

> Joe,
> As  others have said you are slipping out of sync. I modified a motor 
> once and checked its sync' by using an oscilloscope (the disc itself 
> tripped an IR beam and then compared it with the mains cycle on a duel 
> channel o'scope)
> It showed itself to be in sync' until I ran it with the added the 
> weight of the electrodes and their holders. Then it would very slowly 
> slip out of sync', with it only 'aligning' with the mains cycle once 
> every couple of seconds. You could actually watch the trace on the 
> scope slowly creeping across the screen, instead of staying stationary.
>
> In my own case (which is unlikely to apply to you unless you are using 
> a motor you have modified yourself) I needed to remove a bit more from 
> the 2HP motor's rotor.  Most likely though it is as John or Garry 
> suggests: Voltage drop; motor size; phase controller. My favourites 
> being the first two: especially motor size.
>
> Have fun.
> Phil

   Almost certainly the problem was the windage loss rather than the 
added weight itself.  Turns out that disks rotating at high speeds pump 
a lot of air from the middle to outside and that causes significant 
retarding torque.  As I recall the windage increases as the cube of the 
speed and the fifth power of the disk diameter.

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