CFE-SS APPROACH FOR SALIENT-POLE SYNCHRONOUS GENERATORS UNDER UNBALANCES .2. BALANCED AND UNBALANCED RECTIFIER LOADS

This work details the formulation and application of a time-stepping c oupled finite element-state space (CFE-SS) model of salient-pole synch ronous machines supplying electronically commutated rectifier type loa ds. The formulation of the synchronous generators' state-space (SS) fl ux linkage governing differential equations was carried out entirely i n the natural ABC frame of reference, which is coupled to a time/rotor stepping finite element (FE) magnetic field-machine winding inductanc e profile computation model. The impact of synergism between space and time harmonics on damper bar time-domain current profiles and losses, iron core losses, various machine winding current, voltage and torque profiles/waveforms is studied here for a 2-pole, 120 kVA, 24000 r/min , 115 V (L-N) aircraft generator. It is shown here that the rectifier load operation could increase iron core losses and damper bar losses b y as much as 28.31% for balanced and by 66.16% for unbalanced rectifie r load operation, in comparison to regular balanced impedance loads.