[GreenKeys] Machine speed and VFDs

[Nick England]

Teletype Corp certainly thought they were synchronous motors. There is a
starting capacitor in the M28 LMU, but no run capacitor.
http://www.navy-radio.com/manuals/tty/295B-6504.pdf

Also see TTY motors ilustrating Wikipedia (I know, I know)
https://en.wikipedia.org/wiki/Synchronous_motor


Nick England K4NYW
www.navy-radio.com

On Mon, Sep 3, 2018 at 3:16 PM, Scott Johnson <scottjohnson1 at cox.net> wrote:

> As far as I know, they are induction motors, permanent split capacitor.
> That's what I have in my model 28s.  The Governed motors are in another
> class, being brush-type machines.  In order for a motor to run a true
> synchronous speed, it must either have a DC- excited revolving field rotor,
> or a permanent magnet rotor.  Induction motors will run at a fairly
> constant
> speed with a prescribed amount or "slip" if they are designed and specified
> properly, typically a 4 pole 60 Hz motor will run around 1750 RPM lightly
> loaded (versus 1800 RPM for a synchronous machine).  The so-called BLDC
> (brushless DC) motor is really a synchronous machine, having a PM rotor
> with
> a three phase stator, driven by a three phase inverter driver.  Single
> phase
> induction motors can be made to run at precise speed by driving them with a
> variable voltage/variable frequency signal, and using hall effect sensors
> to
> feed back actual speed. Obviously that technology did not exist in the
> industrial market when the model 28 was in vogue.
>
> Scott V. Johnson W7SVJ
> 5111 E. Sharon Dr.
> Scottsdale, AZ 85254-3636
> H (602) 953-5779
> C (480) 550-2358
> scottjohnson1 at cox.net
> scott.johnson at ieee.org
>
> -----Original Message-----
> From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net
> >
> On Behalf Of jim at k6ccc.org
> Sent: Monday, September 3, 2018 11:03 AM
> To: Green Keys <greenkeys at mailman.qth.net>
> Subject: Re: [GreenKeys] Machine speed and VFDs
>
> Scott Johnson said (in part):
> > I doubt you can do this effectively with a PSC single phase induction
> motor,
>
> Unless I'm mistaken, Teletypes used synchronous motors, not induction.
>
> Interesting idea.
>
>
> 73
> -----
> Jim Walls - K6CCC
> jim at k6ccc.org
>
>
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