Search

This paper assesses the post-demagnetization performance of interior permanent magnet (IPM) ac machines by employing the more accurate recoil line approach based on a 2-D transient finite-element analysis (FEA). The method predicts continuous demagnetization of each magnet element undergoing partial demagnetization and evaluates the machine behavior after an event of short-circuit faults across its terminals. Along with the short-circuit faults, a failure in a drive controller or a position sensor, which may lead to a reverse voltage across the machine terminals that can eventually be more fatal and can cause significant reduction in the performance due to high levels of demagnetization, is analyzed as the worst case scenario. The FE predicted post-demagnetization performance is validated by experimental measurements in which a six-phase IPM machine designed for electric vehicle traction is allowed to lose its synchronization with the inverter when forced to operate on a torque–speed envelope, which is way beyond the drive voltage setting. [ABSTRACT FROM AUTHOR]

A 6-phase fractional-slot-per-pole-per-phase interior permanent magnet (IPM) machine having a novel topology of 18-slot, 8-pole and a 6-phase, 48-slot, 8-pole IPM with distributed windings, both designed for a segment-A electric vehicle, are assessed for the risk of partial irreversible demagnetization under various fault conditions. This paper describes a more accurate approach of demagnetization assessment based on 2-D transient finite-element analysis. It is shown that due to the presence of low-order space harmonics in the fractional-slot IPM machine, the demagnetization risks across all pole pairs are different. Compared with the distributed wound machine, the fraction-slot machine is less vulnerable to demagnetization due to relatively high winding inductance, although its demagnetized regions are not uniform in each pole. It is also shown that although the demagnetizing current of one 3-phase short-circuit (SC) is greater than that of 6-phase SC, the resultant demagnetization risk is lower than that of 6-phase SC in the fractional-slotmachine. [ABSTRACT FROM AUTHOR]

This paper proposes a generic approach to reduction of magnetomotive force (MMF) harmonics in permanent-magnet machines with multiple three-phase concentrated windings. Analytical equations for the MMF distributions of the proposed multiple three-phase concentrated windings are derived, and the principle for harmonic cancellation is established and validated by finite-element analysis. A new 18-slot 14-pole nine-phase winding machine in which all sub-MMF harmonics are eliminated is presented based on the proposed generic approach. The proposed approach is also applicable to other slot–pole combinations with concentrated windings except for slot number being equal to 1.5 times the pole number. Retaining all the advantages of the concentrated windings, the new technique improves the fundamental winding factor, enhances the fault tolerance capability, and reduces the detrimental effects of lower and higher order MMF harmonics on the machine, such as high rotor eddy-current and iron losses, less reluctance torque, acoustic noise, and vibration. [ABSTRACT FROM AUTHOR]