Small punch tests on circular specimens were conducted using hemispherical tipped punches on Chromium–Molybdenum (Cr–Mo) steels of varying thermal histories. Combinations of punch diameters and sample thicknesses were used to obtain load–load line displacement (LLD) responses of these steels. Characteristic load, displacement, and energy values at transition points on LLD curves were identified and their dependency on punch diameter and sample thicknesses were studied. From the studies, sample thicknesses in the range of 0.4 to 0.5 mm and a punch tip diameter of more than 1.7 mm have been suggested to be used for the application of the SPT test procedure in the assessment of mechanical properties of in-service Cr–Mo steel components.
In this paper, a new multilevel inverter topology with modular and non modular design is developed, which can be operated both symmetrical and asymmetrical mode with a reduced number of power switches. The proposed design has four separated DC sources and Nine active power switches. The topology can be used with symmetrical and asymmetrical voltage source configuration to generate seventeen and seven voltage levels. This structure can be cascaded to produce maximum level by a series connection to produce higher voltage levels with less voltage stress on the switches without modifying the topology structure. Comparison is made with existing topology and recently introduced topologies based on the number of active switches, Separated DC sources, number of gate driver circuits. To prove the presented topology’s superiority, a simple Multicarrier pulse width modulation has been deployed as the switching scheme. Validation on the viability of the proposed topology has been carried out through Matlab/Simulink simulation.
KEYWORDS : Modular, Non Modular Multilevel Inverter, Reduced Switch.
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