[GreenKeys] 14-15-19 Etc. motor

[Bruce Gentry]

Universal motors  within their ratings are constant horsepower rather 
than constant speed.  By design they have relatively few turns in the 
series field winding and  run best at  higher speed while developing 
less torque than an induction or synchronous motor of equal HP.  
Unloaded, they will reach very high speeds, but if bogged down can 
deliver great torque.  If you are testing a governed motor from a 
Teletype without a  mechanical load, the resistor across the governor 
contacts can cause the speed to rise above governed speed. The resistor 
is to reduce  arcing on the governor contacts by carrying some of the 
load so the motor gets controlled nudges up to correct speed instead on 
purely on/off. The higher RPM also allows the flywheel action of the 
armature and governor to help in smoothing  the speed.

      Bruce Gentry, KA2IVY


On 7/5/18 6:24 PM, Jim Haynes wrote:
> One of the gear set charts I have shows 25 and 50 Hz sync motors - and
> those use the same gear sets.  Which says that the 50 Hz motor is four
> pole, 1500 RPM and the 25 Hz motor is two pole, 1500 RPM.
>
> One of the curiosities of all this is that the speed governed motors for
> Model 15 and friends ran at 2100 rpm, hence requiring different gears 
> from
> the sync motors.  Whereas in Model 28 all the motors run at 3600 RPM so
> sync and governed motors use the same gear sets.
>
>
>