Proposed bearing has increased stability. Magnetic structure keeps inner and outer bearing halves aligned. Electronic feedback circuit keeps bearing radially centered

Studer, P. A.

English

NASA Technical Reports Server

Housinç
inslstor 
Coil
October 1975
	 B75-10251 
• 
NASA TECH BRIEF 
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. 
Single Radial Magnetic Bearing: A Concept 
.
To support a shaft with stability and to resist 
torsional loads, mechanical and magnetic bearings 
have generally been matched in pairs at opposite ends 
of the supported shaft. Typically, the arrangement of 
magnetic bearings in pairs is complicated by the 
inherent instability of the bearings about axes other 
than that of the shaft being supported. Two 
techniques now are employed to overcome this 
instability: (1) axial separation is increased between 
pairs of bearings; or (2) active controls are used to 
maintain the angular position of the bearings, to 
assure that they lie in a plane at right angles to the 
shaft axis. In practice, the axial separation reduces 
instability at the expense of size, and active controls 
tend to reduce system reliability.
The illustration shows a magnetic bearing capable 
of supporting a shaft without these drawbacks. It has 
a magnetic structure that keeps the inner and outer 
bearing halves alined. An active electronic feedback 
circuit is used to maintain the bearing centered 
radially. The structure approximates the surface of a 
sphere and causes the magnetic flux to flow 
circumferentially in the outer member of the pole 
faces.
!0\	 irgap 
IOuter 
Disk	 \	 L\1 Edge 
.
Ring 
Phototr 
Sensor
Single Radia; Magnetic Bearing: A Concept
(Continued overleaf) 
This document was prepared under the sponsorsh i p of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United Slates
	 information contained in this document, , warrants that such use 
Government nor any person acting on behalf of the United States
	
will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19750000251 2020-03-19T20:15:36+00:00Z
A two-piece permanent ring magnet creates a 
radially-directed magnetic field in the airgap. This 
field maintains both halves of a disk and a ring 
annulus in a common plane. The magnetic flux flows 
radially outward through the arms, via the ring, 
across the airgap, and back to the magnet. Radial 
control of the position of the disks and ring is 
established by vernier magnetic fluxes (derived from 
current-carryin g
 coils), which aid or oppose the 
permanent-magnet flux in the airgap. The pole faces 
of the arms are shaped to approximate the contour of 
a sphere having its center at the center of the disk, 
thus making the bearing inherently stable in torsion. 
Control current is supplied to the coils to change 
the net flux in the airgaps if a disturbance alters gap 
length between the disk and ring. The restoring 
control current, and therefore the applied flux, is 
precisely the amount needed to force the ring and disk 
into the proper radial position. 
Control signals for the coils are derived by a 
phototransistor optoelectronic sensor (as seen in the 
figure) and depend on position and rate-of-change in 
position of the disk and ring. The phototransistor 
emitter/collector path is connected to a positive dc 
source through a resistor. The sensor output voltage is 
dc coupled to the inverting input terminal of an
operational amplifier. The noninverting input is 
connected to a potentiometer slider. The potentiome-
ter is dc energized and is adjusted for the desired 
radial separation between pole faces of the disk and 
ring. The amplifier output signal is fed to a coil driver 
which energizes the windings. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Goddard Space Flight Center 
Code 704.1 
Greenbelt, Maryland 20771 
Reference: T5P75-10251 
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
Patent Counsel 
Goddard Space Flight Center 
Code 204 
Greenbelt, Maryland 20771 
Source: Philip A. Studer 
(GSC-1 1978)
. 
Aft 
Categories: 06 (Mechanics) 
01 (Electronics - Components 
B75-10251	 and Circuitry)


Single radial magnetic bearing: A concept

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