Electronically commutated dc motor has an active fixed field winding, and active fixed armature winding, and passive rotor. By use of brushless dc motor switching technique, motor provides continuous controllable and reversible torque without use of sliding contacts

Studer, P. A.

English

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Winding	 Salient	 Armature Armal Pole 01 Winding
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December 1970	 Brief 70-10691 
NASA TECH BRIEF 
-4r 
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 progam may be directed to the Tech-
nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Brushless Direct-Current Motor with Stationary Armature and Field 
An improved electronically commutated dc motor 
has an active fixed field winding, an active fixed 
armature winding, and a passive rotor. By using the 
well-known brushless-dc-m otor switching technique, 
the motor provides a continuous controllable and re-
versible torque without the use of sliding contacts.
Because no power is dissipated in the rotating 
assembly, bearing life is prolonged and thermal limita-
tions are reduced. 
The rotor, made of a material with high magnetic 
permeability, has a number of salient poles or teeth 
and is rotatably mounted near the field winding 
Figure 1. Cross-Sectional Magnetic-Circuit Diagrams of
Halves of Two Forms of the Motor 
Unlike a permanent-magnet motor which has a 
single linear speed-torque characteristic and a unique 
peak efficiency operating point, the new motor can 
be controlled to shift the peak of its efficiency curve 
to match the instantaneous load condition over a 
wide range of speeds. High starting torque is pro-
vided by less power, and magnetic losses at high 
speeds are minimized by a simple control scheme 
such as connected all or part of the field winding 
in series with the armature. Stationary mounting 
of the field results in a rotor structure that may 
have less mass than earlier brushless dc motors. 
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
so that the winding electromagnetically,
 induces 
magnetic flux in the poles. The armature windings 
are also mounted near the rotor. In operation, 
the magnetic flux induced in the poles interacts 
with the current passing through the armature wind-
ings. This current flow is controlled by a solid-state 
commutator (Fig. 2) as in a brushless dc motor. 
The magnitude of the current supplied to the field 
windings controls the motor's speed. The windings 
can be connected in a series, shunt, or compound 
configuration as desired. 
Wear-prone elements are eliminated, and mechanical 
(con tin ued overleaf) 
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=19700000668 2020-03-17T01:03:07+00:00Z
v+ 
Armature 
Control 
Input
R4
Field 
Control 
Input 
Figure 2. Simplified Circuit Diagram of Solid-State Commutator
. 
and magnetic losses in the rotating structure are 
reduced. The motor's inertia is reduced, its re-
sponse time is improved, and its dynamic braking 
and acceleration torques may be controlled. The 
new motor is electrically, magnetically, and mechan-
ically inexpensive and uncomplicated. The fact that 
the field flux can be connected in various con-
figurations makes the invention flexible. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer. 
Goddard Space Flight Center 
Code 207.1 
Greenbelt, Maryland 20771 
Reference: TSP70- 1.0691
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Royalty-free nonex-
clusive licenses for its commercial use will be granted 
by NASA. Inquiries concerning license rights should 
be made to: 
Patent Counsel 
Mail Code 204 
Goddard Space Flight Center 
Greenbelt, Maryland 20771
Source: P. Studer 
Goddard Space Flight Center 
(XGS- 05290)
. 
Brief 70-10691
	
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Brushless direct-current motor with stationary armature and field

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