Interior Permanent Magnet (IPM) machines with spoke-type design are very attractive for several applications, including vehicle traction, which requires a good flux weakening performance to achieve high speed. For this purpose, a high demagnetizing current is usually injected to reduce the machine flux at high speed, with detrimental effect in terms of efficiency. This problem can be mitigated by equipping the rotor with a mechanical flux weakening device which activates during high speed operation by centrifugal force. This paper addresses the analytical modelling of this special kind of IPM motor through a simplified Magnetic Equivalent Circuit (MEC) approach which incorporates saturation and slotting effects as well as the flux weakening device operation. It is shown how the MEC model can effectively describe the IPM machine behaviour despite its simplicity. Results are successfully validated by comparison both with Finite Element Analysis (FEA), which requires much more computational resources, and with measurements from laboratory prototype testing.

Large medium-voltage electric machine stators are usually equipped with form wound coils made of flat conductors (strands) and embedded in open (rectangular) slots. Air-gap magnetic flux lines can enter the slot and, sweeping the strands placed nearest the slot opening, induce eddy currents in them. Such eddy currents cause additional losses which can be much higher than usual skin-effect and proximity losses. In order to avoid dangerous overheating and hot spots, the additional losses in question need to be carefully predicted in the design stage. Time-stepping finite-element analysis (TSFEA) can be used for the purpose, which however implies a large computational burden and requires the machine geometry to be modelled in detail. This paper proposes alternative methods based on time-harmonic finite-element analysis (THFEA) simulations performed on highly simplified machine models and with no need to take rotor motion into account. The proposed methods are shown to produce very accurate results, compared to TSFEA, but with very significant time and computational savings.

Modern road vehicles are more and more often being equipped with electric actuators. These are intended to play critical roles in passengers comfort and safety. Among the electrified components onboard road vehicles, one can distinguish electric power steering (EPS) systems, which have been the subject of intensive investigations covering both design and control aspects. The abilities of several AC motor topologies to fulfil the EPS systems’ requirements have been assessed by a large scientific community in both academia and industry. The present work was aimed at the prediction of the electromagnetic features of the flux-switching permanent magnet machines (FSPMMs), with an emphasis on the air gap flux density. The latter was firstly formulated while neglecting the slotting effect at both sides of the air gap. Then, stator and rotor permeance functions, taking into account the slotting effect and the PM flux concentrating arrangement, were incorporated into the derived flux density spatial repartition. Moreover, the accuracy of the latter was improved through two dedicated correction functions that take into account the rotor position and the magnetic saturation. The last part of the paper presents a simple approach to enhance the developed torque of FSPMMs in an attempt to meet the EPS requirements.

This paper deals with an investigation of the steady-state and transient performance of the direct rotor flux-oriented control (RFOC) strategies implemented in symmetrical two-phase induction motors (2PIMs). Such an investigation is structured within a comparison study considering: 1) the case of a two-leg voltage source inverter (B4-inverter), and 2) the case of a three-leg voltage source inverter (B6-inverter), in the stator of the 2PIM. Following a presentation of both drives, the principle of the RFOC is briefly recalled. Then, a special attention is paid to the implementation of the direct RFOC on current-regulated B4- and B6-inverters. The control of the power switches is achieved by two two-level hysteresis regulators in the B4-inverter rather than three in the B6-inverter. Initiated by a simulation-based analysis of the selected steady-state features of both 2PIM drives under direct RFOC strategies, the comparison study is then extended to a deep experimental investigation of the steady-state operation with emphasis on the dc-link capacitor voltages, the stator line-to-line and phase voltages, stator phase currents, the rotor flux, and the electromagnetic torque. The established results reveal three major limitations of the B4-inverter fed 2PIM drive, such as: 1) unbalanced dc-link capacitor voltages at low speeds; 2) a reduced speed range due to the low level of the phase voltages; and 3) an injection of harmonics due to the d-q transformation. While the B6-inverter exhibits balanced dc-link capacitor voltages in the total constant torque region with higher ripple of the stator phase currents and of the electromagnetic torque, the experiment-based comparison is achieved by an investigation of the dynamic behaviors of both drives under step- and ramp-shaped reversals of the reference speed. It highlights the poor dynamic behavior of the B4-inverter fed 2PIM drive under both shapes of speed reversal.