Re: A more accurate approach to machine induction motor rotors tobecome synchronous

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

Original poster: "Finn Hammer by way of Terry Fritz <teslalist-at-qwest-dot-net>" <f-h-at-c.dk>

Hello RMC, all

Thanks for digging up, and sharing this tidbit.

It seems like a good rule of thumb for 4 pole motors (1500~1800 RPM) but
i doubt that it works with a 2 pole motor (3000~3600 RPM). I think that
in the latter case, you`d end up with too much material removed.

Cheers, Finn Hammer

Tesla list skriver:
 >
 > Original poster: "RMC by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<RMC-at-richardcraven.plus-dot-com>
 >
 > Various rules-of-thumb have been written, regarding the amount of rotor
 > material to be machined off to make flats to enable synchronous operation.
 > This has usually been in the form of "remove a 1 inch depth of material" or
 > " make the flats 2 inches across" etc. etc.
 >
 > These rules don't take into account the rotor size in the first place,
 > whereas a 1939 text by Veinott, published by McGraw-Hill, discusses the
 > method a little more precisely.
 >
 > Chapter 15, titled "Synchronous Motors", describes the process of
 > calculating the size of the flats thus:
 >
 > "... it is recommended that the easiest way [to make a non-synchronous motor
 > become synchronous] will probably be to mill flats on the rotor surface,
 > equally spaced, there being as many flats as there are poles. The total area
 > of these flats should be approximately 40 per cent of the total cylindrical
 > area of the rotor before the flats are milled ... The motor should be able
 > to carry roughly about one-third its nameplate rating".
 >
 > So, if people want to get their rotors to lock up *and* avoid removing more
 > material than necessary (torque suffers as a result), this is the approach
 > to use rather than just assuming a set depth independent of rotor size.
 >
 > Cheers
 >
 > RMC, England