Charles Michael Stephens

Fault detection and management system for fault-tolerant switched reluctance motor drives

The unique characteristics that promote the switched reluctance motor (SRM) for fault tolerance capability, i.e. its ability to continue operation despite faulted motor windings or inverter circuitry, are discussed. It is shown that the magnetic independence of the motor phases and the circuit independence of the inverter phases permit the SRM drive to continue operation with one or more phases disabled. Winding fault detectors indicate the existence of faulted motor windings, and control circuitry acts to block the gating signals to the semiconductor power switches of the affected phase, thus removing excitation from the faulted winding and halting damaging effects that can result from the continued excitation of a faulted winding. The drive an continue operation without the faulted phase.<<ETX>>Fault-tolerance characteristics of the switched reluctance motor are discussed, and winding fault detectors are presented which recognize shorted motor windings. Logic circuitry in the inverter blocks the power switch gating signals of the affected phase at the receipt of a fault-detection signal from one of the fault detectors. The fault detectors were implemented on a laboratory drive system to demonstrate that faults can be contacted on a running drive system and be instantly detected and isolated without causing damage to the inverter and without causing drive misoperation.<<ETX>>

A line-start permanent magnet motor with gentle starting behavior

The line-start permanent magnet motor combines a permanent magnet rotor for best motor efficiency and an induction motor squirrel-cage rotor to permit starting on a conventional AC power source. Three new concepts have been introduced to improve starting performance by eliminating objectionable torque pulsations during the starting interval. A new rotor concept, called the divided magnet rotor, has been devised to provide the best compromise between the magnetic needs of a permanent magnet rotor and the magnetic needs of an induction motor rotor. Here, the rotor slots superficially resemble that of a double-cage induction motor rotor, but the top portion of the slot contains a block of permanent magnet material openly exposed to the airgap. The bottom portion of the slot is devoted to the squirrel-cage. There are more rotor slots than poles, and the magnet polarities are arranged to form the desired number of poles for the intended running speed. The second new concept is the separate starting armature. The stator has two armatures, a running armature having the same number of poles as the magnets, and a starting armature having at least one fewer pole-pairs than the running armature. The starting armature accelerates the rotor by induction motor action, and the power source is switched over to the running armature when synchronous speed of the running armature is attained. The third new concept is an automatic synchronizer that switches the power source when the conditions of optimal speed and optimal electrical phase difference on the running armature are met.

Advanced permanent magnet machines for a wide range of industrial applications

This paper provides an overview of four distinct applications of advanced permanent magnet machine technologies. It describes the specific application benefits that are accomplished with permanent magnet solutions for Oil&Gas, aviation, automotive, and wind turbine applications. The technology development for these four first-of-a-kind machines is presented, each of which advancing the state of the art in power density, torque density, or speed.