Efficiency Evaluation of a dual-inverter supplied open-end three-phase 5 Hp Induction motor drives

This paper discusses efficiency of Variable Speed Drive (VSD) of dual-inverter fed a three-phase 5 Hp open-end winding induction motor. The motor is controlled using equivalent Space Vector Carrier Based PWM. VSD System is modelled using Matlab/Simulink meanwhile inverter and motor are modelled using Simscape Blockset. Simulation result shows that efficiency VSD using dual-inverter is significantly improved in comparison with VSD using two-level inverter. At modulation indices 0.15 – 1.15, efficiency of the system using two-level inverter is in the range of 20% - 82% which is improved by 36% to 97% for the system fed by dual Inverter at full Load (20 N-m). The improvement of efficiency of VSD system with dual-inverter is caused by improvement of inverter efficiency by 76%-98%, compared with efficiency of two-level inverter (44%-93%) while efficiency of motor is relatively the same in the range of 45% to 89% for both inverter structures under investigation. Improvement of efficiency is in line with improvement of quality of inverter output voltage of the dual-inverter over the two-level inverter. Furthermore, it is also found that the efficiency of system is reduced by the reduction of motor load. At very low load, the reactive power (Q) becomes higher than the active power (P), which means the power factor of system become very low (less than 0.5)