Bearings reduce friction by allowing air of vacuum gaps between rotating members through properly-applied magnetic fields. Advantages: There is no physical contact between rotor and support structure; bearings operate directly in vacuum environment without lubrication; and there is unlimited operating lifetime, independent of speed

Veillette, L. J.

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Axial	 Axial 
Gaps	 Gaps 
September 1974	 B7440131 
NASA TECH BRIEF r7 ASA Goddard 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. 
Magnetic Bearings with Combined Radial and Axial Control 
Large spinning structures such as large electrical 
motors and generators develop significant frictional 
forces in the bearings located between rotating members. 
These forces cause bearings to wear rapidly, increasing 
the frequency and cost of maintenance. As a solution 
to this problem, magretic bearings have been developed
which reduce friction by allowing air or vacuum gaps 
between the rotating members through properly-applied 
magnetic fields. The simplest designs use active axial 
control and passive radial alignment. A new magnetic 
bearing permits both axial and radial control in a 
relatively simple structure. 
Control 
Voltages 
Permanent 
Magnet
04 
Stator
02
Rotor 
Permanent 
Magnet 
.
Nonmagnetic 
Shaft
--Central 
Cylinder	 Bearing 
Portion
	
	 Axis
Magnetic Bearing (One Half Shown)
(continued overleaf) 
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will be free from privately owned rights. 
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The magnetic bearing as shown in the illustration 
separates a radially-overlapping outer stator and an 
inner rotor. Under no load the stator and the rotor are 
held coaxially aligned with each other and with the 
bearing axis. Radial and axial forces between stator and 
rotor are controlled by magnetic forces concentrated in 
four axial gaps. These gaps are located between the 
interleaved portions of the rotor and the stator. 
Four magnetic circuits are included in the bearing to 
produce four flux paths, 01 through 04 , which cross the 
axial gaps. Two of these circuits comprise two aligned 
permanent magnets, providing oppositely-directed flux 
paths 01 and 02 . The other two fields, 03 and 04 , are 
provided by a pair of coils, N 1 and N2 . The coils are 
driven simultaneously with pulse-width-modulated cur-
rent pulse trains I I and 12 in response to axial-force and 
radial-stiffness commands. 
When the rotor is radially displaced from the stator 
by some disturbing force, the reluctance of flux paths 
i and 02 increases, which tends to decrease their 
magnitude. A circuit feeding coils N 1 and N2 is used to 
determine the proper current pulse widths to either 
Increase or decrease the bearing radial stiffness. The sum 
of the pulse widths of 1 1 and 12 produces flux 
magnitudes in 03 and 04 to produce the increased 
stiffness. Axial control is accomplished in a similar way; 
however, the axially restoring force between the rotor 
and the stator is determined from the difference in the 
current pulse widths.
Other important advantages of magnetic bearings are: 
There is no physical contact between the rotor and 
the support structure. 
The bearings can operate directly in the vacuum 
environment without lubrication. 
There is virtually unlimited operating lifetime, inde-
pendent of speed. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Code 207.1 
Greenbelt, Maryland 20771 
Reference: TSP74-10131 
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning nonex-
clusive or exclusive license for its commercial develop-
ment should be addressed to: 
Patent Counsel 
Goddard Space Flight Center 
Code 204 
Greenbelt, Maryland 20771 
Source: Leo Veillette of 
Goddard Space Flight Center
(GSC.l 1551)
W. 
S 
B74.1013l	 Category 06, 03,07,02


Magnetic bearings with combined radial and axial control

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