Intrinsic stress effect on fracture toughness of plasma enhanced chemical vapor deposited SiNx:H films

The apparent fracture toughness for a series of plasma enhanced chemical vapor deposition SiN_x:H films with intrinsic film stress ranging from 300 MPa tensile to 1 GPa compressive was measured using nanoindentation. The nanoindentation results show the measured fracture toughness for these films can vary from as high as > 8 MPa⋅√m for films in compression to as low as < 0.5 MPa⋅√m for the films in tension. Other film properties such as density, Young's modulus, and hydrogen content were also measured and not observed to correlate as strongly with the measured fracture toughness values. Various theoretical corrections proposed to account for the presence of intrinsic or residual stresses in nanoindent fracture toughness measurements were evaluated and found to severely underestimate the impact of intrinsic stresses at thicknesses ≤ 3 μm. However, regression analysis indicated a simple linear correlation between the apparent fracture toughness and intrinsic film stress. Based on this linear trend, a stress free/intrinsic fracture toughness of 1.8 ± 0.7 MPa⋅√m was determined for the SiN_x:H films.     

Calculating Short-Circuit Currents with Contributions from Induction Motors

Chapter 7 of a forthcoming book, Recommended Methods for Calculating AC Short-Circuit Currents in Industrial and Commercial Power Systems (IEEE Violet Book) is discussed. The book will be one of the IEEE Standards Board ``Color Book' series of Recommended Practices prepared by the Industrial Power Systems Department of the IEEE Industry Applications Society. (It is being developed under IEEE Project Authorization P551.) The chapter describes the nature of induction motor short-circuit current contributions, discusses calculating techniques, and examines the simplified methods of accounting for induction motor contributions described in ANSI C37 Circuit Breaker Standard Application Guides. An extension of these simplified methods is recommended to eliminate the possible need for duplication of calculations. Examples of calculations are included. For this chapter, it is assumed that other chapters in the ``IEEE Violet Book' cover the purpose of short-circuit calculations, calculating methods available, and details of calculations involving passive power system components and synchronous machines.     

A Case History of Motor Current Contribution to an Industrial System Short Circuit

Oscillograph recordings made during a severe primary short circuit on an industrial power system include the total three-phase currents contributed by plant motors to the fault. An analysis of the recorded motor current contribution to estimate the initial magnitude and time variation is described as well as a calculation of the motor contribution using procedures of ANSI standard application guides. Results are presented for easy comparison of the values obtained from the oscillogram and the standard calculation.