Introduction. Cascaded H-bridge multilevel inverters (CHB-MLI) are becoming increasingly used in applications such as distribution systems, electrical traction systems, high voltage direct conversion systems, and many others. Despite the fact that multilevel inverters contain a large number of control switches, detecting a malfunction takes a significant amount of time. In the fault switch configurations diode included for freewheeling operation during open-fault condition. During short circuit fault conditions are carried out by the fuse, which can reveal the freewheeling current direction. The fault category can be identified independently and also failure of power switches harmed by the functioning and reliability of CHB-MLI. This paper investigates the effects and performance of open and short switching faults of multilevel inverters. Output voltage characteristics of 5 level MLI are frequently determined from distinctive switch faults with modulation index value of 0.85 is used during simulation analysis. In the simulation experiment for the modulation index value of 0.85, one second open and short circuit faults are created for the place of faulty switch. Fault is identified automatically by means of artificial neural network (ANN) technique using sinusoidal pulse width modulation based on distorted total harmonic distortion (THD) and managed by its own. The novelty of the proposed work consists of a fast Fourier transform (FFT) and ANN to identify faulty switch. Purpose. The proposed architecture is to identify faulty switch during open and short failures, which has to be reduced THD and make the system in reliable operation. Methods. The proposed topology is to be design and evaluate using MATLAB/Simulink platform. Results. Using the FFT and ANN approaches, the normal and faulty conditions of the MLI are explored, and the faulty switch is detected based on voltage changing patterns in the output. Practical value. The proposed topology has been very supportive for implementing non-conventional energy sources based multilevel inverter, which is connected to large demand in grid.
In the present investigation, welding of 1 mm thick Ti-6Al-4V sheet has been done by Pulsed Wave (PW) Nd-YAG laser with a variation of laser power from 100 to 400 W and welding speed from 4 to 6 mm s −1. The microstructure and microhardness of the fusion zone indicate that the finely serrated and regular plate-shaped microstructures and the resultant hardness in the welds are the key factors behind the enhanced tensile strength of all joints. The weld bead size increases with decreasing welding speed and vice versa. The hardness increases around the heat affected zone as compared to that of the parent metal, and it is the maximum at the centre of the welded region. In the investigation, the tensile strength of specimen with different process parameters has been found to be approximately equal to the tensile strength of the parent metal. In XRD analysis, the weld zone has been found to consist of 78 % α and 22 % β peaks where two β-titanium peaks (bcc) 100 occur at 39.5110 • and 56.9120 • .
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