And the three-phase motor in this case is being driven by a ' vfd '
These are wonderful devices which take in single phase AC, rectify it and
spit out three phase AC at variable frequencies (not just the plain old
60/50 Hz).
The advantage with these is that when you are running machinery, you get
almost full torque over the entire speed range. Using a variac to control a
motor gives some variable speed capacity but the torque curve is horrid.
Most vfd (variable frequency drives) have a control voltage input so you
__might__ be able to do a loop - put an encoder on the motor shaft and use
an Arduino to generate the control voltage to keep the motor in sync with
the powerline frequency. You could implement variable phase with a counter.
That might be a really cool project...
Dave
> -----Original Message-----
> From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Phil
> Sent: Thursday, September 18, 2014 02:57
> To: 'Tesla Coil Mailing List'
> Subject: Re: [TCML] Resin or fiberglass perfboard for terry filter?
>
> >>" The motor is a 3 phase 208v 1/2 horse driven by a vfd.
> Does it make
> sense to grind flats on it's armature?"
>
> DON'T try grinding a three phase motor, AFAIK that only works
> on single
> phase units
>
>
> Regards
> Phil Tuck
>
> www.hvtesla.com
>
>
>
>
> -----Original Message-----
> From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Dave Boyle
> Sent: 18 September 2014 02:38
> To: tesla@xxxxxxxxxx
> Subject: Re: [TCML] Resin or fiberglass perfboard for terry filter?
>
> The motor is a 3 phase 208v 1/2 horse driven by a vfd. Does it make
> sense to grind flats on it's armature?
>
>
> On 09/17/2014 08:50 PM, David Speck wrote:
> > Dave,
> >
> > "Pretty close" is not good enough. When your gap drifts far enough
> > away from optimum synchronization, the NST will fail permanently.
> >
> > Look at the old posts that describe how to file flats on a motor
> > armature to convert it to a fully synchronous motor. Then, you can
> > use a Freau phase adjuster to precisely set the phase angle of the
> > motor without having to mechanically rotate the motor body.
> >
> > (Another) Dave
> >
> > On 9/17/2014 7:12 PM, Dave Boyle wrote:
> >> Oh now you tell me! Hey what about if I operate my spark
> gap motor in
> >> the synchronous zone? At 1 or 2 beats per cycle with the
> nst switched
> >> off while the motor changes speeds? I have an led strobe synced to
> >> the ac line light that I use to see when the disc is at the right
> >> position. I can't get a phase lock but I can keep it pretty close.
> >> Maybe I should build a custom inverter that will run the motor at
> >> only those speeds that are safe.
> >
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