ON FAULT TOLERANCE INCREASE OF SWITCHED RELUCTANCE MACHINES
Loránd SZABÓ, Member, Mircea RUBA
Abstract: The Switched Reluctance Machine (SRM) is
ideal
for
safety critical applications
(aerospace,
automotive, defense, medical, etc.) where it is desirable
that the electrical drive system to be fault tolerant. The
phase independence characteristics of the SRM enable it
to operate (at lower power and higher torque ripples)
also under partial phase failure conditions. Its reliability
can be improved during its conception stage by applying
special fault tolerant designs and in its exploit by
monitoring its condition and applying fault detection
techniques. In the paper first the most typical faults and
their detection methods are summarized. In the second
part of the paper a fault tolerant SRM structure is
proposed and analyzed by means of simulations. The
obtained results emphasize the usefulness of fault
tolerant SRMs.
Index Terms: switched reluctance machine, machine
faults, fault tolerant, cosimulation.
I. INTRODUCTION
It is well-known that the switched reluctance
machine (SRM) possesses unique characteristics that
promote it for fault tolerance capability: the ability to
continue its operation despite faulted motor windings
or inverter circuitry. The only effects of a fault are the
power reduction proportional to the number of faulted
phases out of total phases and the increase of torque
ripple.
Because of the magnetic independence of the
SRM's phases and the circuit independence of the
inverter phases, a fault in either a motor winding or an
inverter phase can be detected and isolated with no
effect on the other phases. Hence the SRM can
continue its operation also with one or more phases
disabled. Winding fault detectors can indicate the
existence of faults, and these can be isolated by the
intelligent motor controller.
In contrast, winding faults of a polyphase ac
machines have more serious consequences. A fault in
one phase seriously affects the operation of