Procedure for measuring the current in each phase of a three-phase device via single current sensor

Abstract

A method for measuring the current in each phase of a three-phase motor ( ) by the sensor ( ), the motor ( ) being controlled by a plurality of switching devices (S -S ) that receive pulse width modulation signals from a controller ( ). In one embodiment, a first and second sampling window (t and t ) are monitored. When both the first and second sampling windows (t and t ) are less than a minimum sampling window (mw), the voltage pulse trains associated with the highest output (V_h) and the lowest output (V_l) are shifted to form a first modified sampling window (t ′) and a modified second sampling window (t ′). When the first sampling window (t ) is less than the minimum sampling window and the second sampling window (t ) is greater than the minimum sampling window (mw), then the voltage pulse train associated with the highest output (V_h) and/or the middle output (V_m) may be shifted to form the first and second modified sampling windows (t ′ and t ′). When the first sampling window (t ) is greater than the minimum sampling window (mw) and the second sampling window (t ) is less than the minimum sampling window (mw), then the voltage pulse train associated with the lowest output (V_l) and/or the middle output (V_m) is shifted to form the first and second modified sampling windows (t ′ and t ′). The method may then sample a first current and a second current during the first and second modified sampling windows (t ′ and t ′), respectively. The third current may be calculated based on the sampling of the first and second currents.