Re: better sync motor mods (tests)

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

Original poster: "Finn Hammer by way of Terry Fritz <twftesla-at-uswest-dot-net>" <f-hammer-at-post5.tele.dk>

snip

> 
> Question;  has anyone made their flats only 1/3rd the rotor diameter
> for a 3600 rpm motor, and did it work fine?
> 
> John Freau

John, all

Yes, the 0.25kW motor for the rotary in the RAT coil is modified just
like that: Flats are 1/3 the rotor diametre.
Pls. keep in mind that this is a 220 volts motor. It drives a transverse
bar with 2 electrodes at 11 inch diametre sweep. This motor locks in
sync at 205 volts, and looses it again at 190 volts.
I seem to have observed that the motors here in europa tend to have long
rotors of small diametre, compared to american types?

Anyway, the kind of motor makes a difference too:
I have just, for the first time, modified a motor with a start cap and
centrifugal switch. 0.25kW -at- 1500 rpm. Without further considerations i
started out with 4 flats, 1/3 as wide as the rotor diametre. Result: A
motor that locks in at a modest 95 volts, and doesn`t loose it before
the voltage drops to 65 volts, driving the same 11 inch rotor. Starts to
sound bad from 200 volts, and up, although the current is not exeeding
the (RAT)ed 2,1 amp.
So it seems that motors with start cap need smaller flats, compared to
motors with only the run cap.

I have 3 more of these motors
250W -at- 3000 RPM
370W -at- 1500 and 3000 RPM, and I will take more care when I modify these.

Cheers, Finn Hammer