[GreenKeys] order motor

[Don Robert House]

AND NOW WE KNOW THE REST OF THE STORY!

MANY THANKS JOHN



On 21 Jul 2006, at 12:43 PM, John Lawson wrote:



On Fri, 21 Jul 2006, Don Merz wrote:

> Just curious--why 3 phase?



   Most simple selsyns (also called 'synchros') have a three-phase  
stator (fixed) winding, and a single-phase (rotating) rotor. One  
connects the stators together wire-for wire, at whatever distance  
between the units, and then excites the rotors with local single- 
phase AC, with the provision that the AC derives from the same  
source, ie. the AC on both rotors is in-phase.

  Then, torque applied to the shaft of one unit is reproduced at the  
shaft of the other.

   This is the simplest method of hook-up - it gets rapidly more  
complex from there - in fact these units make great analog computing  
elements - the huge Navy fire-control computers on the big destroyers  
were an amazing assembly of selsyns, servos, gearing, etc - they took  
in firing-table data, weapon and projectile info, target range and  
bearing, ship's motion (in real time) and then electrically trained  
the guns to put that shell on the target, by factoring in all those  
parameters (and more) .  Not bad for late-30s - early 40s analog  
computing tech.


   I have several pairs of these motors, BTW - was just playing  
around with a couple of the big brass units yesterday.  The classic  
Ham application was to couple one to the antenna rotor and have the  
other in the shack with a compass rose attached, or a little model of  
the Beam protruding thru a world-map, centered on one's QTH...


   Cheers

John  KB6SCO

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