A modified load commutated inverter-fed induction motor drive system

A new modified load commutated current source inverter (MLCCSI) induction motor drive that employs a standard load commutated current source inverter (LCCSI) together with a voltage source inverter system connected to the machine side, as a utility power interface (UPI) is presented. At normal operation, the LCCSI supplies the power demanded by the motor and the UPI compensates the harmonic power, providing part of the reactive power required to accomplish the natural commutation of LCCSI thyristors. This operational condition results in machine sinusoidal currents. The UPI is also employed for starting up the induction machine and for achieving a suitable performance at the low speed operation range of the drive. The proposed motor drive topology is interesting since it presents a competitive benefit/cost ratio in comparison with the standard schemes. Experimental and simulation results are presented to validate the feasibility of the proposed motor drive system.