Abstract-This paper compares the many fault tolerant threephase ac motor drive topologies that have been proposed to provide output capacity for the inverter faults of switch short or open-circuits, phase-leg short-circuits, and single-phase open-circuits. Also included is a review of the respective control methods for fault tolerant inverters including two-phase and unipolar control methods. The output voltage and current space in terms of components is identified for each topology and fault. These quantities are then used to normalize the power capacity of each system during a fault to a standard inverter during normal operation. A silicon overrating cost factor is adopted as a metric to compare the relative switching device costs of the topologies compared to a standard three-phase inverter.Index Terms-Inverter faults, phase-leg short-circuits, silicon overrating cost factor (SOCF), single-phase open-circuits, three-phase inverter, three-phase ac motor drive topologies.

Characterizing the structure of fault zones is necessary to understand the mechanical, fluid flow and geophysical properties of the lithosphere. This paper provides a detailed characterization of two large-displacement, strike-slip fault zones of the San Andreas system in southern California, the Punchbowl and North Branch San Gabriel faults. The faults cut crystalline and well-lithified sedimentary rocks, and consist of broad zones of fractured and faulted rock (damage zone) containing one, or more, narrow, tabular zones of highly sheared rock (fault core). Subsidiary faults and fractures of the damage zone formed in response to stress cycling associated with slip. The fault core is composed of very fine-grained, altered fault-rocks that reflect high shear strain, extreme comminution, and enhanced fluid-rock reactions. The characteristic and relatively ordered structure of these large-displacement faults is consistent with progressive damage accumulation over the lifetime of the fault. Layers of ultracataclasite containing mesoscopic slip surfaces within fault cores record extreme localization of slip at the macroscopic and mesoscopic scale. Progressive accumulation of ultracataclasite from abrasive wear along a slip surface throughout faulting history can explain the particle size distribution, layered structure, and sharp boundaries of the ultracataclasite layer. The longevity and relative stability of the slip surface is evidenced by the accumulation of progressively younger ultracataclasite towards the slip surface. Although not a common feature, the incorporation of slivers of wall rock into the ultracataclasite layer document occasional branching of the slip surface within fault cores. The damage-zone and fault-core characterization may be used to describe the geophysical, mechanical, and fluid-flow properties of brittle fault zones in crystalline and well-lithified sedimentary rocks of the continental crust. fault zones is necessary to understand the mechanical, fluid flow, and geophysical properties of the lithosphere.Our current understanding of the mesoscopic structure of large-displacement, strike-slip fault zones primarily results from study of uplifted and exhumed faults (e.g., Little 1995;Chester and Logan 1986; Flinn 1977) and faults exposed in mines and drill core (e.g., Ohtani et al. 2000;Wallace and Morris 1986). Early petrographic study of mylonites and cataclasites initiated considerable research into the classification and origin of fault rocks (for review, see Snoke and Tullis 1998). The most commonly used fault-rock classification schemes are based on particle size, fabric and cohesion. For example, in Sibson's 1977 classification, mylonites and cataclasites both are distinguished by primary cohesion and tectonic grain size reduction, but mylonites have a well-developed foliation with some evidence of syntectonic recovery and recrystallization, whereas cataclasites have random fabrics and microstructures indicative of cataclasis. The breccia-gouge series is distinguished by lack of primar...

Abstract-This paper compares the many fault tolerant threephase ac motor drive topologies that have been proposed to provide output capacity for the inverter faults of switch short or open-circuits, phase-leg short-circuits, and single-phase open-circuits. Also included is a review of the respective control methods for fault tolerant inverters including two-phase and unipolar control methods. The output voltage and current space in terms of components is identified for each topology and fault. These quantities are then used to normalize the power capacity of each system during a fault to a standard inverter during normal operation. A silicon overrating cost factor is adopted as a metric to compare the relative switching device costs of the topologies compared to a standard three-phase inverter.Index Terms-Inverter faults, phase-leg short-circuits, silicon overrating cost factor (SOCF), single-phase open-circuits, three-phase inverter, three-phase ac motor drive topologies.

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