Expansion of the Current Reconstruction Areas for Three-Leg Two-Phase Inverters with Three-Shunt Resistors

초록

For measuring the phase currents in two-phase motor drives driven by a three-leg inverter, the leg shunt sensing method using the shunt resistors inserted below the lower switches of the inverter can be used for cost saving. In this case, the three-leg shunt sensing method using the three-shunt resistors of the inverter can widen the measurable current areas more than the two-leg shunt sensing method only using the two-shunt resistors on its two-phase legs since it can reconstruct the immeasurable currents in the two-leg shunt method. However, under high voltage modulation conditions, there are the certain operation areas where the currents cannot be accurately reconstructed using this three-leg shunt sensing method. Due to those areas, the voltage utilization of the inverter is reduced, and the torque ripple and noise of the AC motors are induced. In this paper, we analyzed the current reconstruction areas in the three-leg shunt sensing method of the three-leg two-phase inverter with a CPWM (Continuous Pulse Width Modulation), and proposed a scheme to expand the areas. The proposed scheme can expand those by decreasing the areas in which the currents cannot be reconstructed by half utilizing a DPWM (Discontinuous PWM) method, resulting in improved the voltage utilization of the inverter.

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