Solid state three-phase counter circuit reverses the direction of rotation of a multiphase motor without changing the phase wiring of the supply current source

Fairbanks, A. F.

English

NASA Technical Reports Server

March 1966	 Brief 66- 10 101 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Ring Counter Circuit Switches Multiphase Motor Direction of Rotation 
Winding A
Winding B I Winding C 
Flip-Flop 1
	 ..._,	 L.......l
	
Flip-Flop 2	 __, L___._I	 Flip-Flop 3
Second 
Pulse Source	 i	 Pulse Source 
SwitchLJ 
The problem: 
To reverse the direction of rotation of a multiphase 
motor without changing the phase wiring of the sup-
ply current source. Present relay-operated systems are 
bulky and present maintenance problems due to con-
tact arcing and burning. 
The solution: 
A solid-state three-phase counter in which the 
phase sequence of the counter and hence the direction 
of rotation of the motor are readily reversible.
How it's done: 
The three flip-flops have high current output ter-
minals connected to the three individual phase wind-
ings of the three-phase motor, which is a stepper or 
indexing motor having a permanent magnet rotor 
that aligns itself with the field produced by the wind-
ing that is energized. 
In operation, the pulse sources each supply pulses 
at a repetition rate of 180 per second since the motor 
is 60 cps, three phase. With the switch connected to 
(continued overleal) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19660000101 2020-03-11T17:35:09+00:00Z
the first pulse source, the initial pulse turns flip-flop 
1 on and current is applied' to winding A of the 
motor. The second pulse switches flip-flop 1 off and 
flip-flop 2 on, thus removing current from motor 
winding A and applying it to motor winding B. The 
third pulse switches flip-flop 2 off and flip-flip 3 on, 
removing current from motor winding B and applying 
it to motor winding C. The fourth pulse switches flip-
flop 3 off and flip-flop 1 on and the sequence is re-
peated. 
To reverse the motor direction of rotation, the 
switch is connected to the second pulse source and the 
above-described action is reversed with flip-flops 3, 2, 
and 1 being turned on and off in that order, thus pow-
ering motor windings C, B, and A in that order.
Patent status: 
Title to this invention covered by U.S. Patent No. 
3,112,433 has been waived under the provisions of 
the National Aeronautics and Space Act (42 U.S.C. 
2457 (f)) to Space Technology Laboratories, Inc., 
One Space Park, Redondo Beach, California. 
Source: Avard F. Fairbanks

of Space Technology Laboratories, Inc., 
under contract to

Jet Propulsion Laboratory
(JPL-SC- 166)
.. 
Brief 66-10101	 Category 01


Ring counter circuit switches multiphase motor direction of rotation

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