Research Of Low Speed High Torque Permanent Magnet Direct Driving Motor's Pole-Slot Combination

The using of Low Speed and High Torque PMSM(LSHTPMSM)omits reduction gears of traditional drives,and due to the advantages of LSHTPMSM,such as good performance,high efficiency and easy maintaining,more and more attentions have been attracted to it.LSHTPMSM is usually used to be power machine,so it is necessary for LSHTPMSM to make sure that the output torque is smooth,saving energy and simplifying manufacturing process.The number of poles is many and the frequency of excitation is low for LSHTPMSM,so there could be too many pole-slot combinations to choose.The selection of pole-slot combination is one of the major questions for LSHTPMSM due to the influence on the magnet circuit and winding's arrangement.In this dissertation,fractional pole-slot combination is studied by thinking about reducing torque fluctuation and iron core loss.The ratio of poles and slots is usually big for LSHTPMSM,so the greatest common divisor and lowest common multiple of poles and slots can't correspond to cogging torque's peak value.Based on formulas of cogging torque,studying the relationship between the number of period and pole-slot combination,using the ratio of lowest common multiple and greatest common divisor to represent the reducing effect of pole-slot combination to LSHTPMSM's cogging torque.According to the analysis of reducing torque fluctuation and iron core loss for LSHTPMSM,the selection of pole-slot combination should make sure that the suppression to harmonics of flux density in air gap and induce voltage is good enough,besides it,the damage to foundation wave is weak.According to the alternating current motor winding theory and cell motor method,summarizing the principle of cell LSHTPMSM's poleslot combination,then studying the relative position between the slot and pole influences harmonics of flux density in air gap.Based on Fourier harmonic analysis,decomposing flux density wave into permanent magnet excitation component and notch causing distortion,calculating the relative position that could reduce low orders harmonics mostly.In this dissertation,deducing the equation of fractional slot winding cell motor's harmonic winding factor,then making sure that the suppression and damaging degree of different pole-slot combinations to harmonics of induce voltage and foundation wave.In this dissertation,six different fractional slot winding pole-slot combination have been selected,and three pole-slot combinations belong to concentrated windings,three pole-slot combinations belong to distributed windings.According to building models and simulating infinite element software,contrasting the harmonics' situation of flux density and induce voltage belong to six models,then certifying the principle of how pole-slot combination reduce these harmonics.Based on this,illustrating that concentrated winding pole-slot combination is appropriate for motors with rated speed below 100r/min and distributed winding pole-slot combination is appropriate for motors with rated speed exceed 100r/min by thinking about the manufacturing technique LSHTPMSM...