Controlled capacitor 1-phase a.c. PM generator FEM characterization and circuit model based performance

This paper presents an attempt to design a high efficiency (90%) 3kW, 3000/3600rpm, 220/240Vrms, 50/60Hz, around (8+2) kg, one phase ac autonomous generator with simplified voltage control of max. (+/- 5%) steady state error. A two salient pole stator, PM rotor configuration with heavily saturated stator core was necessary to reduce the machine reactances well below 1.0 p.u., while also reducing stator weight. Only a surface PM rotor with thick magnets and 0.8 PM span per pole pitch ratio produced at full load Xd=0.30p.u. Xq=0.70p.u.(end coil leakage included) which enhanced the machine power (reactive and active) to reduce the required variable capacitor that controls the generator voltage from resistive load to 0.8 lagging power factor load. The paper introduces the new topology and a preliminary sizing methodology followed by FEM characterization with steady state performance evaluation. A circuit model with parameters imported from FEM and a PI voltage control via a terminal capacitor variation is proposed and show the capability to deliver 3kW at both 3000 and 3600rpm for 0.8 power factor RL loads, with stable response to step load transients and acceptable short circuit current.