Large power PWM IGBT converter for shaft alternator systems

The use of shaft alternators in marine application is well known as a convenient and efficient way to supply all the electrical loads of a ship with two main purposes: sharing active and reactive power with the auxiliary generators installed on board and operating in stand alone configuration when the ship travels at cruising speed. An innovative shaft alternator system based on PWM (pulse width modulation) inverters has been designed and installed in year 2002: this solution guarantees high performance operation without the need of installing a synchronous compensator, as requested by the up to now widely used LCI based system. This paper describes the 1440 kW, 440 V, 60 Hz PWM IGBT shaft alternator developed and installed on 5 R_o-R_o (Roll On-Roll Out) car carrier vessels (214 mt, 56700 GRT (Gross Registered Tonns)), actually cruising on North and South Atlantic Routes. Two 2200 kW, 690 V, 50 Hz PWM IGBT water cooled shaft alternators were also designed and realized during 2003 and all factory tests were successfully completed.