Modified Steady-State Analysis of the Current-Source Inverter and Squirrel Cage Motor Drive

The "modified" steady-state analysis of the current-source inverter (CSI) drive given in this paper includes the effects of the following factors neglected in the ``conventional\´\´ analysis given in present literature: 1) the variation of the ac back electromotive force (EMF) of the induction motor (load) during commutation, and 2) the phase shift of the fundamental component of the line current due to the finite commutation interval. It is shown that the effective leakage inductance of the motor during commutation is lower than the value obtained by the low-frequency blocked rotor test. A procedure for measuring the effective leakage inductance is given. At high stator frequencies the inverter operation is influenced by the conduction of series diodes outside their usual 120° period. A method of calculating the ``critical\´\´ frequency where this effect begins to occur is given.