[Back]

A. Schulz, M. Schneeberger, J. Wassermann:
"A Reliability Analysis of Switching Amplifier Concepts for Active Magnetic Bearings";
Talk: IEEE International Conference on Industrial Technology (ICIT 2006), Mumbai; 12-15-2006 - 12-17-2006; in: "Proceedings of ICIT2006", (2006), ISBN: 1-4244-0726-5; 6 pages.

Active magnetic bearings (AMBs) allow a lubricant and friction
free support of structures, e.g. rotors. Important advantages of this
ecologically friendly technology are that there is no systematical requirement
for maintenance as well as the possibility to adjust bearing parameters
to various operating conditions. The most significant drawback of
AMB-technology is that even a single failure within one sub-assembly may
cause a break down of the bearing load capacity. The risk of an unintentional
machine standstill combined with the resulting costs is one major
reason that the broad industrial acceptance of active magnetic bearings is
quite low at the time.
To increase AMB reliability at reduced costs a new AMB concept has
been developed by the authors. It comprises a highly integrated DSP controller
and a reliable switching amplifier (RSA) along with a spatial and
galvanic isolation between the digital controller and the signal conditioning
circuitry from the power units.
To investigate the increase in reliability using the RSA instead of standard
industrial switching amplifier an analysis of the RSA as well as a comparison
with industrial switching amplifier concepts is presented in this paper.
Considered are the failure rates of the individual components and subcircuits,
the circuit topologies as well as different maintenance strategies. It
is shown that the mean time to failure (MTTF) of the RSA is up to a factor
of 21 higher compared with conventional industrial switching amplifier
concepts.