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Re: SRSG motor anomoly
>
> Original Poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net>
> > Original Poster: "Mark Broker" <broker-at-uwplatt.edu>
Hi Mark,
Regarding the first paragraph in my reply, I may be incorrect. That was the
info I dug up a couple years back, and it worked for me, but maybe not in
everycase. I wrote Reinhard Buchner off list wishing him well. In his reply, he
also included comments on the first paragraph of my reply to you. I thought
this should go to the list as more info to consider.
Take care,
Bart
>The flats (which you grinded and/or filed) should be equal
>with the ungound areas between the flats. Grinding more
>away will not help the torque.
Here's Rienhard's comments:
I donīt think so. If you remove / keep equal amounts on the
rotor (=> equal surface area), you will be losing torque. You
want the poles, which you create, to be as large as possible.
The poles are the unground surfaces. These should be exactly
as large as the run windings are wide. What you want to do is
make the rotor "pole" exactly as large as the run winding "pole".
That is the only way you can extract the maximum amount of
torque in my opinion. In my syncīd motor the cuts are about (very
rough guess here) 1/3 of the pole (the unground material) width.
I think, once you start removing more material than described
above, you will start losing flux lines, because the poles are now
smaller than the winding. I.e. the winding creates flux lines, which
never pass through the rotor, once it has locked into place, thus
you lose this bit of torque, they otherwise would create. Imagine
what would happen, if you did this to a 3600 rpm motor. You
would have to remove 1/2 (if Iīm thinking straight) of the rotor
surface to get equally ground and unground areas. The resulting
poles would be quite small ;o)) Most likely the motor would also
start drawing more current.
Here is a snip from a post that I sent to the List a while ago on
my sync work:
Start of snip:
First run was successful. The motor "kicked in" much harder
than before the modifications. From the new "sound", I was
pretty sure it was synchronizing to the mains, but I needed to
know for sure, so I chalked a cross on the rear of the shaft and
used a handheld FL-light to have a look. The FL light acts as a
sort of cheap stroboscope (50Hz "flicker"). The chalk marks produce
a refractionating pattern (sorry I donīt know the technical name for
them). On a normal induction motor these patterns "float" slowly
around (opposite to the rotational direction). The donīt "fix" (sync)
in one spot. On my modified motor, the patterns lock into place (the
same place every time the power is turned on) very neatly. I turned
down the variac to about 110V. You could hear the motor trying to
hold itīs sync at this voltage. Every time it fell out of sync, you
could feel (and see via the FL light) the motor "kicking" back into
sync. At full voltage, I had a really hard time slowing down the
motor. As soon as I released the shaft, the motor kicked back into
sync position. Next was a speed measurement. As expected with
a 4 "pole" rotor, it now ran at 1500 rpm (opposed to the 1450 rpm
measured earlier) at 50Hz. The last measurement was a current
measurement. The motor now pulls 1.72A (instead of 1.43A). I
think the current draw is still very reasonable. Every time I slowed
down the rotor (using a rag to prevent skin burns) far enough to
get the motor out of sync, the current jumped to about 3.2A, until
I released the rotor and it synchronized to the mains again (and
the current dropped back to the 1.72A). Absolutely neat!!
End of sniplet
Iīll agree with the rest of your post, tho ;o))
Take care and yes, letīs stay in touch,
Reinhard