Re: Phase controller question.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: FutureT-at-aol-dot-com 

In a message dated 6/28/04 2:20:15 AM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:

>Hello John, All.
>
> >I don't understand why the motor would change from a 220V motor
> >to a 90 volt motor after modification.
>Me, too. But I had it running one time when received it from an ebay seller
>and it sounded completely normal and quiet at 220V.
>'though this already proves it was a 220V unit I double checked the
>nameplate and wiring instructions and there is not even a way to wire it for
>110V,
>the only plausible alternative in europe, thers is only wiring to be made
>for clockwise / counterclockwise operation.


Christoph,

Well now I'm curious about what's really happening.  Normally the sound
doesn't change too much as the voltage is varied for a motor.  So
this motor has 220V written on the rating plate I suppose?


> > I understand that the motor may lock into sync at 90 volts, but generally
>the full supply voltage
> >is supplied to the motor anyway.
>This was, what I experienced with the other motors ( only 2 ) I modified for
>other RSG's before. They sounded normal at 220V but got a little warmer than
>prior to grinding flats.


Well that's good that you've modified other motors, so you're familiar
with the process and the results.  Did the armature and coils seem
more or less like a normal induction motor?  I guess you ground 2 flats?


> > Did you rewind the motor
> >windings or something?
>
>No. Only new paint and new bearings. rewinding a motor woulb be a bit too
>advanced for me ;-)
>
> > If you supply only the minimum voltage
> >that can lock the motor into sync, then it may lose sync under load
> >when the rotor is attached.  Or perhaps you have the rotor attached
> >already?
>
>I have the complete rotor disk attached. When I have it running at 90V under
>fluorescent light I can see how it syncs. When I take a cotton cloth and
>press it against the spinning disk, I can see how the angle of the attached
>pattern slowly moves  ca 30 degree away and then the motor looses sync (
>This can be heard and seen clearly ). It really takes pretty much force (
>additioinal loading ) to get the motor out of sync. Strange....


You're judging the sync lock range by slowing the disk with a cotton
cloth?  So you haven't tried it with the phase controller yet?  Do you
mean it's strange the motor is so powerful even at 90 volts?  Maybe
the motor is more powerful than needed for the rotor size?  This is
OK of course but may explain why it easily stays synced.  But it
doesn't explain why it won't run smoothly at 220V assuming it is a
220V motor.


> > Generally if the motor is run at such a low voltage, it
> >may have trouble remaining sync'ed over the full variac phase
> >controller range.
>
>I still had no chance to veryfy this, but at least it does not sound as if
>it was loosing sync. But I will ckeck this when I have my fluorescent lamp
>back.
>
> > Maybe the system is only giving a
> >limited phase adjustment range because you're feeding the motor
> >such a low voltage?
>
>This of course might be true. In this case it seems like I will have to set
>the phase manually....., anyway, this worked before there were phase
>controllers.


I don't know what cap value you should use, but you did say you
get the 8V resonant rise which sounds good.  But did you say that
you get only a 30 degree phase shift with the phase controller?  Or
was that with the cotton braking method?


> > I would use 220 volts for the motor and not
> >use the stepdown transformer unless something unusual is going
> >on that I don't know about in your system.
>
>The sound and rapidly rising current draw of the motor force me to stay at
>90V. Even at 110V the sound becomes somewhat awesome...


That's interesting about the awesome noise.  Can you describe it
more fully?  Is it a vibrating, a chattering, a roaring, a moaning,
a screaming?  Quite a mystery though.


>The good news is: I made a blown static RQ-gap yesterday from scrap parts
>and made a first run with it today. Together with the finally fixed
>MOT-Stack
>I at least was able to achieve 4,5 feet streamers at ca 2,5KVA ( non PFC )
>and performance was fery smooth. I never thought a static gap could perform
>this good
>in a maggie. The gap setting was still pretty narrow and resulted in
>something that sounded at bit higher than 200BPS. So I think it is not
>unrealistic to expect 6feet when the RSG finally runs properly ant the
>MOT-stack has its 6th MOT back.


Yes, that sounds reasonable.  A static gap usually can perform pretty
well on a Maggie since the overall coupling is similar to that of a classic TC.

John


>Thanks for your feedback
>
>best regards
>
>Christoph Bohr
>