Assumption or Fact? Line-to-Neutral Voltage Expression in an Unbalanced 3-Phase Circuit During Inverter Switching

This paper discusses the situation in a 3-phase motor or any other 3-phase system operating under unbalanced operating conditions caused by an open fault in an inverter switch. A dc voltage source is assumed as the input to the inverter, and under faulty conditions of the inverter switch, the actual voltage applied between the line to neutral (open neutral) of the 3-phase circuit is derived, based on the inverter switching table. This issue is very important, since during motor analysis and simulation it very often becomes necessary to use a line-to-neutral voltage as input to the simulation process or analysis, for which current is the output. The paper studies the necessary and sufficient conditions required for the line-to-neutral voltages indicated in the switching truth table to be true.