Research On The Thrust Characteristics Of Slotless Tubular Permanent Magnet Linear Motor

Slotless tubular permanent magnet linear motor(PMLM) does not contain the cogging structure, meanwhile its lateral core don’t split, so this kind of structure of the motor only contain longitudinal edge side effect, moreover the air gap of motor is big, which leads to the armature reaction of primary is small, so slotless cylinder PMLM is becoming more and more widely used in direct drive occasion because of the smooth operation and large range of thrust. Enhancing the overall thrust of the motor output is the key under the background of research of the linear motor, at the same time, analyzing the influence of the side effect of linear motor to the thrust is of great significance in improving precision and performance of motor. The text considers slotless cylinder PMLM as the analysis object to carry out the research about thrust characteristics of the motor from the increase of thrust and inhibition of motor thrust fluctuation respectively. Due to the larger flux leakage, which causes slotless cylinder PMLM lower magnetic load, therefore carry out the magnetic field law analytical analysis and size optimization of the convex-shape poles, so that improve the motor thrust from the aspects of increasing the magnetic load of motor. The motor winding fever regularity in the virtual slot is analyzed by using thermal circuit method and the optimization of winding structure is done in order to improve the peak value of the motor thrust from the aspects of increasing of the thermal load capacity. In view of the side effect of cylinder PMLM, the primary side end magnetic field and its optimization is analyzed in order to reduce the thrust fluctuation of the motor.At first this paper analyses the particularity of the magnetic circuit structure of the slotless structure compared with the slot ones, and the main dimensions of the motor are determined by adopting the combination of magnetic circuit method and finite element method, then the thickness of magnetic poles and length of air gap on the influence of air gap flux density are analysed, in addition the thickness of primary iron core and the thickness of primary winding motor simulation on the influence of thrust output are analysed respectively, and the rule of motor electromagnetic load distribution is analyzed and the preliminary optimization of the related parameters of the motor is completed.Secondly the vector magnetic potential method based on the boundary is done to process the analytical calculation in order to obtain the magnetic field distribution of the convex-shape poles. in addition the influence of size of the convex-shape poles to the magnetic flux leakage coefficient and the thrust is analyzed based on the result of the magnetic field analytical. at last the effect in the promotion of thrust of the convex-shape poles compared with the traditional rectangle type magnetic pole is analyzed through the contrast. The prototype of slotless cylindrical PMLM is manufactured, and the no-load back EMF and static thrust experiment are carrued out. The correctness of the enhancing thrust of convex pole is verified.Then the virtual slot winding thermal resistance distribution by using thermal network is deduced, through analyzing the internal structure optimization of the slot winding, which lead to the changing rule of the internal heat resistance, and the motor temperature rise is compared before and after the optimization, and then simulation is done to verify its effectiveness in the promotion of peak thrust. In addition the convex-shape poles in the inhibition of magnetic flux leakage to improve motor load and motor load reduction effect is analyzed. The correctness of thermal optimization is verified by the temperature rise test.Finally the magnetic field distribution of the primary core side is analyzed, and analyze the changes of motor magnetic field with the primary iron core movement, and the change law of side to side thrust is obtained on this basis, then the primary core length compensation way is adopted to decrease the thrust fluctuation of the motor, and then the influence of sawtooth end shape of the cylinder PMLM to the output thrust is analyzed. Through the no-load positioning force experiment of the prototype, the effectiveness of the primary core length conpensation in suppressing end effects and inhibiting fluctuations is verified.