Re: Starting a Teletype sync motor question

• To: tesla-at-pupman-dot-com
• Subject: Re: Starting a Teletype sync motor question
• From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Wed, 02 Jun 1999 07:49:54 -0600
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi John,

> Original Poster: FutureT-at-aol-dot-com 
> 
> All,
> 
> I'm using a 50Hz, 3000rpm 1/12th HP Teletype sync motor on 60Hz,
> for 3600rpm in a rotary sync gap.  I tried connecting a 7uF to 30uF,
> cap across the blue and red wire for starting, but it won't start this
> way.  Yellow and blue are connected to the line.  I then touched the
> red and blue wire together with no cap for starting, this works better,
> but the motor still often needs a push to get going, and it makes
> clanking noises as the speed ramps up.  Once it reaches max
> speed, I disconnect the red wire, then it locks up fine.  I've been 
> using this rather awkward method for starting it.
> 
> I realize that Teletype motors usually use an external relay block
> for starting, but different motors seem to be wired a little differently?
> 
> I wonder if the 60Hz on a 50Hz motor makes the starting a little
> more difficult?
> 
> Does anyone have any suggestions or knowledge of the correct
> way to start this type of motor?  Or maybe the motor has an internal
> defect?

This sounds like a motor I acquired recently (from an old projector 
or reel-reel tape deck). It sounds as if, like mine, it's either 
designed to run from a 3-ph supply or a single phase with the cap 
across one winding. The 7uF sounds like even it might be too large a 
value for this motor. Mine uses 2.5uF -at- 50Hz.

?
Malcolm

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