Re: Disintegrating squirrel cages ?

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

Original poster: "Edward Wingate by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ewing7-at-rochester.rr-dot-com>

Tesla list wrote:
> 
> Original poster: "R.E.Burnett by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <R.E.Burnett-at-newcastle.ac.uk>
> 
> Hi Guys,
> 
> Given that the procedure of modifying induction motors by grinding
> flats seems quite common on this list,   I wondered if anyone has
> experienced problems with the squirrel cage rotor breaking-up
> at speed ?
> 
> I have modified a number of small induction motors for synchronous
> operation in the past,  and the depth of the flats has always meant
> that some of the aluminum shorting-bars of the rotor became exposed.
> 
> I had not given much thought to this until it was brought to my
> attention today by a man who is milling flats on a 1.5 HP 3000RPM
> motor for me.  He was concerned that aluminum which is no longer
> covered by the iron laminations could foul the stator due to
> "centrifugal force" when the motor is run at speed ?
> 
> This is a hazard that I had not thought about,  but will stop worrying
> if nobody has experienced any problems.  I guess the rotor is quite
> small,  and 3000RPM isn't really that fast,  but I would be interested
> to hear other peoples thoughts / experiences about this.
> 
>                                                         Cheers,
> 
>                                                         -Richie,

Hi Richie,

I have a 2 HP 3600 RPM Dayton modified-to-run synchronous squirrel cage
motor on the rotary gap for my twin coil and have never had a problem
during the 6 or 7 years it has been in use. I have modified two of these
motors and both have been fine even though there is major exposure of
the aluminum bars. The bars are solidly molded into the rotors at the
time of manufacture. I wouldn't be too concerned. :)

Ed Wingate RATCB