Conventional non-rare-earth permanent magnet (PM) electrical machine can hardly achieve comparable performance with the neodymium iron boron (NdFeB) machine due to the low coercivity and remanence. To solve this probl...
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Conventional non-rare-earth permanent magnet (PM) electrical machine can hardly achieve comparable performance with the neodymium iron boron (NdFeB) machine due to the low coercivity and remanence. To solve this problem, a new kind of electrical machine using only Alnico magnet is proposed in this study. The novel rotor topology eliminates rotor iron core, and thus effectively limits armature reaction and improves torque density. A kind of rapid assessment method for the demagnetisation effect ofqcurrent in different slot-pole combinations through magnetomotive force and winding factor is presented and verified by 2d finite-element analysis. The optimisation of critical dimensions is demonstrated, and the trade-off between high PM utilisation and low demagnetisation effect is emphasised. After that, the good torque-current linearity and robust to demagnetisation characteristics of the proposed topology are proved through a comparison with two rare-earth-free machines. Finally, the performance comparison with a manufactured conventional NdFeB machine under the same volume constraints is provided. The result suggests that the proposed machine has a higher power factor, lower eddy-current loss, and rare-earth PM machine comparable torque density.
This study investigates the influence of rotor topologies and winding configurations on the electromagnetic performance of three-phase synchronous reluctance machines (SynRM) with different slot/pole number combinatio...
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This study investigates the influence of rotor topologies and winding configurations on the electromagnetic performance of three-phase synchronous reluctance machines (SynRM) with different slot/pole number combinations, e.g. 12-slot/4-pole and 12-slot/8-pole. Transversally laminated synchronous reluctance rotors with both round flux barrier and angled flux barrier have been considered, as well as the doubly salient (dS) rotor as that used in switched reluctance machines. Both concentrated anddistributed winding configurations are accounted for, i.e. single-layer anddouble-layer conventional and mutually coupled windings, as well as fully pitched winding. The machine performance in terms of d- and q-axis inductances, on-load torque, copper loss, and iron loss have been investigated using 2d finite-element analysis. With appropriate rotor topology, 12-slot/4-pole and 12-slot/8-pole machines with fully pitched anddouble-layer mutually coupled windings can achieve similar torque capacity, which are higher than the machines with other winding configurations. In addition, the synchronous reluctance machine with round flux barrier can have lower iron loss than dS reluctance machine under different working conditions. The prototypes of 12-slot/8-pole single layer anddouble layer, dS SynRM have been built to validate the predictions in terms of inductances and torques.
This work is motivated by the investigation of the common mode ground current which occurs in induction machines controlled by pulse- width modulation (PWM) at higher frequencies. In order to quantify this current, th...
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This work is motivated by the investigation of the common mode ground current which occurs in induction machines controlled by pulse- width modulation (PWM) at higher frequencies. In order to quantify this current, the common mode impedance of the motor has to be determined. Using the transmission line approach the model parameters are extracted from both two-dimensional (2d) and three-dimensional (3d) field simulations. 2dfinite-element (FE) analysis is an efficient tool for simulating the entire motor cross-section. However, eddy currents in the laminations cannot be modelled explicitly and have to be approximated by a semi-analytical formulation. The study investigates the accuracy of this model for a wide frequency range (10 Hz, . . . , 1 MHz). For this purpose, a specialised 3d simulation tool for induction motors was developed, taking into account the actual distribution of eddy currents in the laminations. Simulation results are presented for a simple one conductor test case as well as for an entire motor cross-section of an existing 240 kW motor.
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