A locus diagram to determine the complete starting performance of a 3-phase induction motor connected to a single-phase supply

A graphical solution, which gives the sequence voltages, starting-torque ratio, line current, the voltage across the capacitor and the corresponding values of a dimensionless admittance ratio for a 3-phase induction motor at standstill and connected to a single-phase voltage, is derived. Several optimum conditions, in particular an exact admittance ratio for minimum unbalance, are obtained from the locus diagram. In all cases it is shown that the admittance ratio obtained is independent of the applied voltage and the locus diagram is therefore applicable to machines of any rating.