Advanced energy storage systems for electric guns and other pulsed weapons
on combat vehicles present significant challenges for rotor bearing design.
Active magnetic bearings (AMB's) present one emerging bearing option with
major advantages in terms of lifetime and rotational speed, and also favora
bly integrate into high-speed flywheel systems, The Department of Defense C
ombat Hybrid Power Systems (CHPS) program serves as an excellent case study
for magnetic bearing applications on combat vehicles. Under the sponsorshi
p of the CHPS program. The University of Texas at Austin Center for Electro
mechanics (UT-CEM) has designed active magnetic bearing actuators for use i
n a 5 MW flywheel alternator with a 318 kg (700 Ib), 20 000 rpm rotor. The
flywheel alternator serves as a power supply for multiple systems on a mili
tary vehicle, including mobility load leveling and weapons systems. Because
of continuous duty requirements, magnetic bearings were chosen for this hi
gh-speed application to minimize losses and to enable the flywheel to meet
a planned vehicle life of 15 to 25 years.
To minimize CHPS flywheel size and mass, a topology was chosen in which the
rotating portion of the flywheel is located outside the stationary compone
nts. Accordingly, magnetic bearing actuators are required which share this
''inside-out" configuration, Because of inherent low loss and nearly linear
force characteristics, UT-CF,M has designed and analyzed permanent magnet
bias bearing actuators for this application. To verify actuator performance
, a nonrotating bearing test fixture was designed and built which permits m
easurement of static and dynamic force. An active magnetic bearing (AMB) co
ntrol system was designed to provide robust, efficient magnetic levitation
of the CHPS rotor over a ride range of operating speeds and disturbance inp
uts, while minimizing the occurrence of backup bearing touchdowns. This pap
er discusses bearing system requirements, actuator and controller design, a
nd predicted performance; it also compares theoretical vs, measured actuato
r characteristics.