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Re: [TCML] Salient Pole Query
Greg,
My understanding was that the dead poles they are talking about in
the article are part of the stator. (although I may have read the
article too quickly.) These dead areas are the few areas where
no wires are threaded through the stator. Their goal is to match the
width
of the flats to those areas. It's possible I mis-understood the article
and they may be refering to an armature with a wound armature.
I can see how in that case it would be important not to grind
through the wires. It was a number of years ago that I last
looked at that article. (Guess I should have reviewed the article :)
In the typical motors that most of us use for or rotary gaps,
there are often no areas that are free of wires in the stator,
so I just ignore the dead pole concept.
Actually since there are start and run windings, it would make
sense (maybe?) to adjust the flat width to the width of the areas where
stator
run windings are threaded, and ignore the start windings. Often
it's very difficult to see these windings properly, so I just ignore
the dead pole concept.
Regarding the armature (or squirrel cage rotor), I agree it's just
laminations with embedded cast aluminum, and it makes no
difference where the flats are ground as long as they're 90
degrees apart for a 4 pole motor.
I think that article has caused a lot of confusion for sync gap
builders. This is why I just suggest to folks that they grind
the flats to be 1/4 the dia. of the armature in width.
John
-----Original Message-----
From: G Hunter <dogbrain_39560@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Mon, 1 Dec 2008 7:18 pm
Subject: Re: [TCML] Salient Pole Query
I've noticed a disconnect between the appearance of actual "squirrel
cage" AC
induction motor rotors and the rotor depicted on the popular web
document. I've
only examined the rotors of smaller motors (used in bench grinders,
pool
filters, and the like). All the AC motor rotors I've inspected were
the same:
an assembly of segmented iron laminations embedded in a cast aluminum
slug. The
alternating iron and aluminum "cage" bars are parallel with each other,
but
skewed with respect to the axis of the rotor (for vibration control, or
so I've
read). There are no wire windings on this sort of rotor, and no "dead
poles"
that I can see. It shouldn't make any difference where the flats are
ground, as
long as they are offset exactly 90 or 180 deg. I'm no motor expert.
Are my
observations and conclusions accurate?
Greg
--- On Mon, 12/1/08, futuret@xxxxxxx <futuret@xxxxxxx> wrote:
From: futuret@xxxxxxx <futuret@xxxxxxx>
Subject: Re: [TCML] Salient Pole Query
To: tesla@xxxxxxxxxx
Date: Monday, December 1, 2008, 4:52 PM
Phil,
Yes, it's because you're in the UK that hte motor
is 1425rpm.
After you modify the motor it will run synchronous at 1500
rpm.
Yes, the motor is suitable.
I always ignore the dead pole concept. I just make the
width of
the flats a certain proportion of the total armature
diameter.
After modification the motor will run hotter and have less
torque.
The dead pole concept may become more important for much
larger motors.
1/4 the dia of armature works well. So if your armature is
3" dia,
then make the flats 3/4" wide. Since you have a four
pole motor,
grind 4 flats.
I show my electronic phase shifter circuit for adjusting
the sync
phase at my website: (also some sync rotary gaps can be
seen there.)
http://futuret.110mb.com
John
-----Original Message-----
From: Phil Tuck <follies@xxxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Sent: Mon, 1 Dec 2008 5:16 pm
Subject: [TCML] Salient Pole Query
Hello.
I am thinking of a SRSG as my next 'project' and
have looked into salient
pole motors converted from induction motors. My own motor
has very little
info on the label so I am unsure as to its suitability.
The website at
http://evolve000.4hv.org/tesla/tc2srsg.html
describes the work involved and my motor does indeed look
similar, although
my armature has individual segments on its surface, whilst
the webpage
example has a plainer looking armature.
Could someone look at my temporary page at
http://homepage.ntlworld.com/follies/temp/temp.html
and let me know if my motor is indeed suitable.
My motor though is rated at 1425 rpm, while the web article
only describes
1750 (needs 4 flats) & 3450 (needs 2 flats) rpm motors
however.
I am UK based at 50 cycles is that the reason for the
difference?
Regards
Phil
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