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Re: Starting a Teletype sync motor question



Tesla List wrote:
> 
> Original Poster: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net>
> 
> 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

Reinhard:

	Non-polarized ELECTROLYTIC motor starting capacitors are very common,
at least here in the US.  Small, cheap, and dry out after a few years.

Ed