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Analysis of Torque Characteristics of Parallel Hybrid Excitation Machine Drives With Sinusoidal and Rectangular Current Excitations

The parallel hybrid excitation machine (PHEM) consists of axial parallel permanent magnet machine part and doubly salient electromagnetic machine part. The three-phase armature windings of two parts are connected in series. Based on the waveforms of back electromotive force, both sinusoidal and rectangular current excitations can be adopted in PHEM. The torque characteristics of PHEM drives with ideal sinusoidal and ideal rectangular current excitations are analyzed. The average torque versus armature current in brushless ac (BLAC) and brushless dc drives are comparatively analyzed. Furthermore, the torque and torque ripple versus current angle in some typical armature currents are investigated. Moreover, the speed and torque waveforms are given under the vector control and the current pulsewidth modulation control scheme. Finally, the experimental data of the target PHEM agree well with the simulation results. It is shown that in BLAC drives, the PHEM exhibits higher torque density with lower torque ripple.