Technology Upgradation with Multi Level Inverter – A Scheme for Life Enhancement of Short Circuit Alternator

Abstract

Short circuit alternator is a specially designed synchronous generator used to supply bulk amount of energy required during testing of electrical power equipment. The alternator discussed here is of 1500MVA rating and can be operable in dual mode i.e. as a motor or as a generator. A static drive based on current source inverter (CSI) is used for motoring operation of this machine. Several phenomena such as high level of harmonics, common mode voltage, shaft voltage, bearing current have been observed in the present system. Eventually all these has a direct or indirect impact on the life of the machine and its journal bearings. A simulation model of the present system and its detailed analysis endorses that the conventional CSI is responsible for those effects. Multi level inverter is a boon to the inverter technology. Existing system is again modelled with the proposed 2-level & 3-level inverters. Results show that 3-level inverter is the best proposition for up-gradation of the present system