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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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