Brushless dc spin motor is designed to use Hall effect probes as means of revolving rotor position and controlling motor winding currents. This results in 3 to 1 reduction in watt-hours required for wheel acceleration, a 2 to 1 reduction in power to run wheel, and a 10 to 1 reduction in the electronics size and weight

Rosenlieb, J. W.

Stern, D.

English

NASA Technical Reports Server

July 1972	 B72-10448 
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
A Brushless D. C. Spin Motor
for Momentum Exchange Altitude Control 
The problem: 
Conventional ac induction motors, when used in 
conjunction with a static inverter momentum wheel, have 
several deficiencies. The system is bulky; it requires too 
many watt-hours to accelerate the momentum wheel: 
and once running, consumes excessive power to keep 
the wheel in motion. 
The solution: 
A brushless dc spin motor (see figure) has been 
designed to use Hall effect probes as a means of resolving 
rotor position and controlling motor winding currents. 
This results in a 3 to 1 reduction in watt-hours required 
for wheel acceleration, a 2 to 1 reduction in power to 
run the wheel, and a 10 to 1 reduction in the electronics 
size and weight. 
How it's done: 
The motor uses a stator (either two- or three-phase 
winding), a main permanent magnet rotor, a flux return 
path ring for the sensing rotor, and two Hall effect 
probes located in the air gap of the sensing rotor. 
Two armature windings, electrically displaced by 90 0 , 
are provided on the stator. The motor is energized by two 
power amplifiers which are controlled by two Hall probes 
that sense the magnetic flux of the auxiliary sensing rotor. 
The sensing rotor is aligned with the main rotor so 
that the voltages of the Hall effect probes are proportional 
to the magnetic flux from the main rotor. By suitably 
magnetizing the rotors, the flux density around the 
periphery of both rotors can be made to vary sinusodially. 
The probe voltages are the inputs to the power amplifiers 
that provide the currents to the armature windings. 
This motor has  normal operating speed of 8,000 rpm 
and an operating life of 9,000 hours. It has a nominal 
torque of 1590 gm-cm and a peak output power of 133 
watts.
Notes: 
1. This innovation may be of interest to designers of 
high speed, high efficiency motors and the aerospace 
industry in general. 
2. Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&TS-TU 
Huntsville, Alabama 35812 
Reference: B72-10448 
Patent status: 
No patent action is contemplated by NASA. 
Source: D. Stern and J. W. Rosenlieb of
General Electric Co. 
under contract to
Marshall Space Flight Center 
(MFS-14952) 
('ateeoFy 06, 02 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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A brushless dc spin motor for momentum exchange altitude control

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