Performance of a line-start single-phase permanent-magnet synchronous motor

There is now widespread experience of three-phase synchronous motors using high-field permanent magnets for rotor excitation and many high-performance designs have been demonstrated in which the magnets are situated in internal slots within the rotor laminations. A cage rotor winding is fitted if asynchronous starting is required. These machines exhibit inverse saliency, with q-axis reactance X_q greater than d-axis reactance X_d, and with a suitable choice of design parameters can yield near-unity power factor and high efficiency at rated load. This paper reports a study of permanent-magnet q-axis synchronous motors with single-phase supply, with a magnetising view to assessing the potential for achieving high efficiency, low-cost drives for use in HVAC and similar reactance applications