| Simple in structure, small in volume, light in weight, little in energy loss, screw pump oil system could decrease oil cost, improve efficiency, and be of widely prospect. Total efficiency of screw pump oil system drived by common motor was higher than beam-pumping unit, but similar to the motor used in beam-pumping unit, it also existted energy loss phenomenon. To settle the problem, a novel energy-saving motor used in screw pump was designed, and this motor could make efficiency of screw pump oil system improved and variable speed device decreasing. In this paper, arrangement scheme of a novel multi-star phase shifted pole changing coil was given and the methods to determine coil split ratio were analyzed. According to electromagnetic theory, 2D electromagnetic mathematical model in which stator windings were spitted coil was developed, and magnetic field distribution of the novel motor at starting was solved by finite element method, starting performance of motor was calculated. Based on energy method, rotor slot leakage reactance under different poles and different loads were calculated, and the variation of rotor slot leakage reactance with loads was gotten. Based on time-step finite element method, distribution of branch current in stator windings and operating performance were calculated and analyzed when branch was unbalance, the method to calculate circulating loss in stator windings of novel multi-star phase shifted pole changing motor was given, and the effects of the loads variation and degree of unequilibrium on circulating loss in stator windings were calculated and analyzed. In the procedure of finishing this paper, some experiments were done so that theoretically calculated results could be tested. By calculating and analyzing above, some useful conclusions were gotten, which could be referred by engineering design.
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