Frequency and phase detector circuit enables a hysteresis synchronous motor to drive a load of given torque value at a precise speed determined by a stable reference. This technique permits driving larger torque loads with smaller motors and lower power drain

Markowitz, I. N.

English

NASA Technical Reports Server

April 1967	 Brief 67-10084 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Circuit Increases Capability of Hysteresis Synchronous Motor 
Crystal Reference 
Ramp I	
^?tor
_H	 + Velocity	 Drive 
vco	 and Phas[nerator	 e Detector
 
The problem: 
To drive a load of given torque value by a high 
speed, high efficiency, low power drain, compact 
hysteresis synchronous motor. In a conventional sys-
tem where it is desired to drive the load at a precise 
speed determined by a stable reference, this type 
motor could not torque the load into synchronism. 
Also, if the motor should momentarily drive the load 
into synchronism from stall, pullout torque would be 
too low to maintain synchronism. Proper pullout 
torque to maintain synchronism, in such a case, could 
only be obtained by starting the motor in a no-load 
condition. 
The solution: 
A frequency and phase detector circuit that deter-
mines the precise moment for switching the synchron-
ous motor from the starting source to the reference 
source. 
How it's done: 
When the motor is to be started, the ramp generator 
delivers a voltage V 1 to the voltage-controlled oscilla-
tor (VCO) to run the oscillator at a low enough 
frequency to drive the high torque load. The ramp 
voltage slowly decreases, continuously increasing the 
VCO frequency as the motor follows in synchronism. 
While operating below the crystal reference frequency, 
the switch (composed of the velocity and phase de-
tector) passes Only the VCO frequency. When the
VCO frequency and crystal reference frequency are 
equal and in phase, the velocity and phase detector 
passes only the crystal-controlled reference. All de-
tection and switching is digitally controlled. 
Notes: 
1. This circuit could be used to obtain maximum 
starting and pullout torque for high speed head-
wheels and fast rewind devices in video recorder 
applications. 
2. This technique permits driving larger torque loads 
with smaller motors having lower power drain. 
3. Inquiries concerning this invention may be di-
rected to: 
Technology Utilization Officer 
Manned Spacecraft Center 
Houston, Texas 77058 
Reference: B67-10084 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: Ivan N. Markowitz 
of Radio Corporation of America
under contract to
Manned Spacecraft Center
(MSC-1080)
Category 01 
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=19670000084 2020-03-11T20:43:57+00:00Z


Circuit increases capability of hysteresis synchronous motor

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