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RE: [TCML] How To Turn A Vacuum Cleaner Motor Into A Synchronous Motor

DWP,
I think there is some misunderstanding here. I don't think the sensor and magnet were triggering the strobe as you do (I think that is what you're thinking?)
The presumption is that the magnet was attached to the motor shaft such that it passed and induced a voltage into a fixed coil once per rev.
If so, the output will always coincide with the electrode passing that point in space. 
If the scope is setup to show both channels overlaid, and the output from the sensor coil is fed into one channel, with the mains fed in on the other channel, and the output from the sensor subsequently always coincides with the same point on the mains sine wave, then the motor is synchronous.  

I use an infra-red sensor being tripped by the electrodes and it work fine.

Regards
Phil

www.hvtesla.com

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of dave pierson
Sent: 07 December 2010 12:34
To: Tesla Coil Mailing List
Subject: Re: [TCML] How To Turn A Vacuum Cleaner Motor Into A Synchronous Motor

> The poster mentions that he had "the mains on the other" [ channel] So 
> I assume a mains reference sine wave on the other channel.
      Good point.  However:

>> In usual engineering use of the term synchronous motor, the speed is 
>> set by the line frequency.  Strobe Testing with a magnet spun by the 
>> same motor as a sync source demonstrates that one end of the motor 
>> (where the magnet is) is 'synchronous' with the other end.

>> If a scope is to hand: most have a 'line sync' position, which syncs 
>> the scope to the _line_ freq.  With line sync selected, a reading 
>> from the flying magnet to a sense coil would be interesting.
 
>> A motor which (happens?) to be running at 3000 (ish) will appear 
>> synchronous to 50 (or 60, or 30 or 100).  A proper synchronous motor 
>> will hold synch Under Varying Load.
     The key is just above.  a 'truly synchronous' motor will
     hold speed, and phase, under varying load and input
     voltage, (within reason...).  

     best
      dwp
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