ANALYSIS OF LCI SYNCHRONOUS MOTOR-DRIVES WITH FINITE DC LINK INDUCTANCE

Steady-state operation of a load commutated inverter (LCI) fed synchro nous motor drive is analysed by means of a digital computer based solu tion of the synchronous machine equations. The solution permits calcul ation of current, voltage, and torque waveforms and includes the effec ts of finite DC link inductance, saliency of the rotor and all machine resistances. The continuity constraints for steady-state operation ar e exploited to enable the proper initial conditions to be calculated d irectly, without the need for iteration. Operating points are describe d by the firing angle gamma0, and the overlap angle mu, and are comput ed for an assumed DC supply voltage of 1.0 per unit. The linearity of the state equations allows the normalised solutions to be scaled to ob tain any desired value of torque, DC link current etc. Sample calculat ions are provided, showing the influence of the DC link inductance on the torque, DC link current and voltage waveforms. These are then comp ared with experimentally measured data taken from a 3 kVA LCI fed sync hronous motor drive, and a good level of agreement is achieved.