# [TCML] Salient Pole Query

G Hunter dogbrain_39560 at yahoo.com
Mon Dec 1 17:18:55 MST 2008

```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 at aol.com <futuret at aol.com> wrote:

> From: futuret at aol.com <futuret at aol.com>
> Subject: Re: [TCML] Salient Pole Query
> To: tesla at pupman.com
> 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 at ntlworld.com>
> To: tesla at pupman.com
> 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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