Re: SRSG Alignment

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

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hi Ian,

Tesla list wrote:

>Original poster: "Ian McLean" <ianmm-at-optusnet-dot-com.au>
>Always open to new ideas.  Thanks for highlighting a good option Bart.  Do
>you have any pictures ?

No. I haven't taken pics of anything in a long time (and Santa didn't bring 
me a digital camera). I'll try to bring home one from work next week and 
takes some pictures. I've been meaning to do this for a while now.

>By the way, hope you don't mind, but I liked your MMC mounting method so
>much I copied it (kind of).  I have mounted my caps on polyethylene backing
>boards (one board per series string), with the bleeders, and then slid each
>string into a PVC stormwater pipe, put on end caps and brass connectors.
>They are 20 inches long and 4 inches wide each, and, like you, I painted
>them bright red.  The caps are joined together with 1/4" copper pipe.
>They
>look great.  I'll take some piccies once I get my digital camera back from
>my sister.

Cool!, love to see it. I'll take pics of my MMC bank also when I get the 
camera.

>Also, I did read the archives on this SRSG alignment issue (before I get
>told off for rehashing an old issue), and got the same sort of idea that
>this method just did not work very well.
>
>However, as a rough guide, is there a correlation between AC peaks and
>stator position ?

Yes by the stator position within the casing, but I'm not sure there is a 
specific position common to motors when mounting the stator (across the 
same model, sure).

> From what you are saying, the peaks will be when the
>flats are lined up with ... what ... the centre of the run windings (this
>makes sense), or the centre of the flats (I would have thought this would be
>the zero crossing points).

Oh, no that's not it. I use 8 rotating for 240 BPS. Thus, I have electrodes 
every 45 degrees.

But regarding your question, the rotor flats position with reference to 
the  electrodes is what you would need to setup (regardless of how the 
stator is positioned). The peaks should line up center "between" flats. If 
you measured from flat edge to next flat edge and mark center on the 
unground portion of the rotor, you should theoretically have the AC peaks 
as the run windings are doing the repelling work. So yes, zero crossing 
should occur at center to the flats.

Again, my modification was to 1800 rpm on a 1/3HP motor. And I use 8 
electrodes, so I have electrodes at peaks and zerocrossings. Optimum 
position on the this setup (in my opinion) is about 22 - 25 degrees past 
peak (VI crossing point).

>So, because I am running at 50Hz, my motor should spin at 1500rpm.  4
>electrodes lined up with the flats will give me 100bps.

4 electrodes positioned 45 degrees from flats should be point of reference. 
If there was a degree wheel attached to the shaft, it would make for 
"certain" positioning from any point of reference. The degree wheel could 
be aligned with the rotor flats in whatever fashion you choose.

>Then I can
>fine-tune by rotating the motor in the cradle and later, when I can afford
>the extra variac, build the JF phase adjuster - which is not really 100%
>necessary, but will allow fine adjustment on-the-fly.  This sound reasonable ?

Agreed. I think the JF phase controller is a real winner for srsg's. My dc 
drive is nice, but it took time to work out the kinks. There's a lot of 
initial bracket alignment and it's critical to ensure the "not so 
stationary" stationary electrodes are center  throughout it's rotation (for 
electrical and crash reasons). Also, the arm "must be" sturdy. The larger 
the disc, the larger the stationary arm, and thus, the greater the play at 
the end. It was fun working through it all, but a lot of work.

Take care,
Bart