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

Hi Gary,
what I can say is, that the diodes become very hot. I have soldered two diodes each 6A in parallel so the current through the diodes I think is more than 12A. Heavy currents are induced when rotating and of course, when the 2 shorted segments are passing the brushes, it's like a short circuit in the diodes with only the stator coils in place. Maybe this is the reason they get so hot.
In my opinion it would even be possible to add some resistors, in series with the diodes?! I think the "poles" in the armature are to strong with only the diodes. I have some commercial sync motors here (arround 80W each) and they have a normal armature like every induction motor and only 2 weak permanent magnets on each side of the short-circuit armature. This is enough to "force" the armature in sync. So I think it might help to put resistors in series with the diodes and keep the poles much weaker. 

Stefan
----- Original Message ----- From: "Gary Lau" <glau1024@xxxxxxxxx> 
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Friday, December 17, 2010 4:22 AM
Subject: Re: [TCML] How To Turn A Vacuum Cleaner Motor Into A Synchronous Motor 



Hi Stefan,

Interesting - thank you for doing and posting this.

Here's my uneducated guess - let me see if any of this makes sense?

It was stated that it was necessary to Variac the mains voltage down
considerably to achieve proper operation.  Could it be that when the motor
was operating in nice synchronous mode, that the applied voltage is roughly 
what would result in 3000 RPM operation of an un-modified motor?  And that
the motor REALLY doesn't like having those diodes in the circuit at anything other than a synchronous 3000 RPM with the diodes aligning with the brushes 
at the mains zero crossing.  So if the RPM is more than 3000, the diodes
start some high-current bucking, resulting in the RPM edging back down to
3000 to achieve no current through the diodes?  I wonder if replacing the
diodes with wires would operate any differently???  It appears that the
applied voltage is very critical, and if it's off very much from a
sweet-spot, it will torture the motor with crazy-mode.

Regards, Gary Lau
MA, USA
On Thu, Dec 16, 2010 at 3:38 PM, Teslalabor <teslalabor@xxxxxxxxxxx> wrote: 


Hello,

today I modified a 400W universal motor from a washing machine. I used 2
diodes each 1kV/6A. I did a scope test which shows that the motor runs
perfectly sync:

http://www.youtube.com/watch?v=yOlfzxzucy8

But there are 2 problems: The motor is not self-starting AND the motor
sometimes runs in "crazy mode", as I call this strange behaviour.
"normal-mode" and "crazy-mode" - both can be seen in the video.

Best Regards
Stefan


----- Original Message ----- From: "Clive Penfold" <
clivepenfold@xxxxxxxxxxxxxx>

To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, December 07, 2010 6:46 PM
Subject: Re: [TCML] How To Turn A Vacuum Cleaner Motor Into A Synchronous
Motor


Phil,

Yes, that is correct. Brief explanation along with some photos here:

http://4hv.org/e107_plugins/forum/forum_viewtopic.php?102515.last

Regards,

Clive




________________________________
From: Phil Tuck <phil@xxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Tuesday, 7 December, 2010 15:10:17
Subject: 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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