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Re: Starting a Teletype sync motor question



Hi Ed,

> Original Poster: Ed Phillips <evp-at-pacbell-dot-net>
>
> "Hi John:
>
> My teletype motor uses a cap marked "88-108 MFD, 125VAC 60 cycles", a
> curious rating.  It measures 137 uF on my c-meter.  It seems to be
very
> lightweight for it's capacitance compared with other motor starting
caps
> I've seen, perhaps because it's only rated for very low duty cycles.
> Maybe the cap you're using is too small?
>
> Regards, Gary Lau
> Waltham, MA USA"
>
> That's most interesting.  Never heard of a TTY sync motor using an
> electrolytic starting capacitor, which is what you are referring to!
> What kind of TTY?

Why do you think this is an electrolytic cap? Gary mentions its
markings say 125Vac. From this, I would guess it is an
unpolarized cap, probably of MP (metal/paper) or MKP (PP)
composition. What makes me wonder is the size (F). For Garys
TTM (teletype motor), this sounds huge. I would have expected
around 50-75% (max) would be enough for this size motor.

Coiler greets from germany,

Reinhard