Influence of Phase Magnetic Couplings on Phase Current Characteristics of Multiphase BLDC Machines with Overlapping Phase Windings

Multiphase brushless dc (BLDC) machines are implemented in electric and hybrid electric vehicle applications due to their high torque/power density, good fault tolerance capability, and low torque ripple. Moreover, the per-phase converter rating can be reduced by increasing the phase number. However, the number of magnetic couplings between phases increases with the phase number, and these magnetic couplings can have an important influence on the machine performance. Therefore, they need to be considered in simulation models and their effect should be considered in control algorithms. Accordingly, the objective of this paper is to analyze the effect of magnetic phase couplings on the performance of multiphase BLDC machines with an overlapping phase winding configuration. First, a detailed electric machine model, in which the machine parameters that are determined by 2-D finite-element method analysis are implemented, is developed. Using this model, the influence of mutual inductances on phase current characteristics with pulse amplitude modulation (PAM) and pulsewidth modulation (PWM) controls is investigated. In addition, a novel PAM-based control strategy, in which the effect of phase mutual inductances is considered, is proposed and analyzed. After demonstrating the influence of mutual inductances on phase current characteristics, the dependence of mutual inductances on the winding configuration is studied. Finally, experimental results with the PAM control and the new PAM-based control are used to validate the simulation results

No-load performance analysis of brushless DC machines with axially displaceable rotor

Brushless dc (BLDC) machines with a surface-mounted permanent magnet (SMPM) rotor meet the high-torque and high-efficiency requirements for automotive applications. However, their constant-power operation region is limited due to the low phase inductance. As an alternative to the electrical field-weakening methods, the speed range of radial-flux BLDC machines can be extended by mechanically reducing the axially overlapping length of the stator and the rotor. In this paper, the no-load performance of an SMPM-rotor BLDC machine with an axially displaceable permanent-magnet rotor is analyzed. The effectiveness of this mechanical field-weakening method is limited through the flux components due to the stator/rotor misalignment and the additional losses. The cause of the flux components due to the stator/rotor misalignment and the dependence of back-electromotive-force waveforms on the axial rotor position are investigated by using 3-D finite-element method (FEM) analysis, where the effects of the end-winding geometry and design are taken into account. Moreover, the additional loss mechanisms due to the stator/rotor misalignment are identified, and the no-load additional losses are determined by using the experimental and 3-D FEM analysis results. Finally, the numerical results are verified by using test-bench measurements

Vorrichtung für eine Elektro-Maschine

Eine Vorrichtung für eine Elektro-Maschine weist auf: einen Stator mit einem Statorträger (211-1811) und mindestens einem Statorzahn (213-1813), der sich in einer axialen Richtung (203-1803) erstreckt und an einem Axialende des Statorzahns an einer ersten Axialposition (321-1721) endet; und einen Rotor mit mindestens einem Permanentmagneten (219-1819), wobei der Rotor relativ zu dem Stator um eine in der axialen Richtung verlaufende Drehachse bei einem ersten axialen Abstand zwischen dem Stator und dem Rotor und bei einem zweiten axialen Abstand (d2) zwischen dem Stator und dem Rotor drehbar ist, wobei mindestens eines der folgenden Merkmale verwirklicht ist: der Statorträger (211-1811) ragt axial über die erste Axialposition (321-1721) nach axial außerhalb des Statorzahns (213-1813) hinaus und/oder der Permanentmagnet (219-1819) ragt sowohl im Falle des ersten axialen Abstandes als auch im Falle des zweiten axialen Abstands (d2) axial über die erste Axialposition (321-1721) nach axial außerhalb des Statorzahns (213-1813) hinaus