Tech Briefs Magazine - August 2023 - 42

Application Briefs
SBS thrust
actuator
Radial
actuator
Axial edge
sensor
Backup
bearing
SBS radial
actuator
Backup bearing
resilient mount
Motor
Impeller
Layout of the in-line blower for the new FBCO2 Scrubber. (Image: Calnetix)
provide significantly improved life with no mechanical limits
on cycles, are tolerant to particle contaminants in the process
airstream, and can operate when exposed to vacuum.
The main design challenge was to fit the new magnetic bearing
blower into the same space as the gas bearing supported heritage
blower. The AMB system with position sensors and backup bearings
had to be miniaturized to fit into a highly constrained space.
To circulate environmental air through the FBCO2
system,
the blower leverages an overhung radial impeller spinning at
up to 60,000 rpm. From the impeller, flow is directed through
the housing and around the centrally located motor section.
Keeping the motor effectively sealed from the process flow
keeps the motor and bearing components free from erosion or
accumulation of contaminants.
Process flow around the motor and magnetic bearings cavity
also provides heat rejection for thermal management of the
stator. Backup bearings provide a mechanical backup function
in the case of shock loads exceeding the load capacity of the
magnetic bearings, or any time the active magnetic bearing system
experiences a fault or loss of power.
To take advantage of the frictionless magnetic bearings system,
the PM motor can operate at very high speeds, providing
improved volumetric and gravimetric power density. The radial
flux surface mount PM rotor utilizes a carbon fiber sleeve to
provide rotor-dynamic stiffness and magnet retention, while
providing improved permeability. With windage as the only
major mechanism for loss, a motor such as this can exceed 98
percent efficiency.
From controls perspective, the AMB is significantly more
complex than legacy mechanical bearings or air bearings.
Speed and position sensors in the stator are utilized to determine
velocity and orientation of the rotor. Electromagnetic actuators
provide the force to center the rotor, counteract dynamic
loads, and safely maintain rotor position with five axes of
42
control. Permanent magnets can be used to bias the AMB system
to offset static loads and reduce control current.
The Calnetix dual electronic controller ties all of this together,
taking inputs from the sensors, driving the speed of the motor,
and controlling the relative position of the rotor. The added
complexity comes with the advantages of the ability to
actively tune the performance of the motor, real-time motor
status monitoring, and prognostic health monitoring of the
blower as well as the connected system.
Long-duration human habitation in space or on other planets
will require efficient, robust, and highly reliable solutions
for the processing of breathable atmosphere and other
health-critical systems. " The unique blower system was successfully
installed by NASA on ISS and has been operating continuously
since February 2023, " said Vatche Artinian, CEO at Calnetix
Technologies.
" This is the first time a five-axis magnetically levitated system
has been commissioned for use in an orbital application and
shows promise as a technology, which can be used across many
other applications, such as fluid pumps, reaction wheels, and
gyroscopes that challenge conventional bearing technologies, "
Artinian added.
Following the validation phase in the current ISS system,
AMB and related high-speed PM motor technologies could further
be utilized in future space missions, such as Artemis, Orbital
Reef, and Mars missions.
This article was written by Matthew Farides, Director of Business
Development, Calnetix Technologies (Cerritos, CA). For
more information, visit www.calnetix.com.
References
Hawkins, L., Filatov, A., Khatri, R., DellaCorte, C., Howard, A., " Design of
A Compact Magnetically Levitated Blower For Space Applications, "
ASME Turbo Expo, Paper GT2020-15090, Sept. 2020, London (Virtual).
www.techbriefs.com
Tech Briefs, August 2023
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Tech Briefs Magazine - August 2023

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