EXPERIMENTAL INVESTIGATIONS ON PERFORMANCE OF LINE COMMUTATED INVERTER FED. RELUCTANCE MOTOR DRIVE

Abstract

A variable speed ac drive is now found to be most suitable with line commutated inverter system. Therefore, in this dissertation this scheme has been used for the reluctance motor drive to experimentally investigate the performance of the system. In this scheme 3-phase uncontro-lled rectifier bridge in combinatio'n1`Wjth,a 3-phase auto-transformer converts fixed frequency and voltage a.c. supply into variable d.c. voltage which is then fed to inverter bridge operating in line commutation mode. Ter-minal voltage sensing method has been adopted to realise the commutation of thyristors and terminal capacitors have been used to supply the lagging reactive power needed for motor and inverter. An analysis is also made on the basis of a developed analytical model. In order to obtain analytical results, . computation with the help ' of computer has also been done. In experimentation and computation the steady state performance of the system has been investigated. The starting methods have also been discussed. The performance of the system under varied conditions are observed which are elaborated. On the basis of the experimental as well as computed results, the system' s feasibility is predicted. The effect of variation of d.c. link voltage Vd and terminal capacitor C on speed control over a wide range has been observed. The validity of the analytical. approach is also established by comparing the computational results with experimental ones.