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This paper proposes two novel partitioned stator hybrid magnet memory machines (PS-HMMMs) having flux-reversal (FR) and switched-flux (SF) topologies, respectively. The PS-HMMM configurations geometrically resemble the magnetically geared machines, which employ PM excitation and armature windings on two separate stationary bodies. The proposed machines offer the merits of alleviating the conflict...
This paper investigates the influence of magnet height on the unbalanced magnetic force in rotationally asymmetric surface-mounted permanent magnet machines without rotor eccentricities. It shows that increasing the magnet height can effectively minimise the unbalanced magnetic force in rotationally asymmetric machines having pole number equal to 3k+1, where k is an integer number. However, the unbalanced...
In switched-flux permanent magnet (SFPM) machines, the 6th-harmonic back electromotive force (EMF) is dominant, whilst the 3rd-harmonic back-EMF is much smaller. This paper proposes several new position estimation methods for sensorless control based on the 6th-harmonic back-EMF. Firstly, by detecting the zero-crossings of the 6th-harmonic back-EMF with/without eliminating the influence of the 3rd-harmonic...
In this paper, a comparison on the on-load performance, such as on-load back EMFs, inductances, on-load cogging torques, torque, torque ripples, and iron losses, amongst the interior permanent magnet (IPM) machines having different slot/pole number (Ns/2p) combinations (Ns±2=2p, Ns±1=2p, Ns/2p=3/2 or 3/4, and Ns/2p=integer) is carried out considering local magnetic saturation. It...
This paper proposes a standstill test method for the determination of electrical parameters of permanent magnet synchronous machine (PMSM) drive system fed by a conventional three-leg inverter. In order to estimate the equivalent total circuit resistance, a self-cancellation method is proposed to eliminate the influence of inverter nonlinearity on the calculation. With the identified equivalent total...
Tooth-tip local magnetic saturation can be significant in surface-mount PM (SPM) machines. In this paper, the influence of tooth-tip local magnetic saturation on the on-load iron and PM eddy current losses is comprehensively investigated in SPM machines having different slot/pole number combinations (Ns±2=2p, Ns±1=2p, Ns/2p=3/2 or 3/4, and Ns/2p=integer). It is found that due to...
The third harmonic current is commonly injected into the fundamental one to improve the output torque of the multi-phase machines. It can interact with the third harmonic back-EMF, contributing to positive torque. However, the output torque may not always be improved with the third harmonic current injection under the same rms value constraint. The optimal ratio of the third harmonic current to the...
In this paper, an external-rotor switched flux hybrid magnet memory machine with a flux-concentration design is developed. Due to the external-rotor configuration, the stator design space is enlarged to alleviate the stator geometric conflictions existed in the internal rotor machine. Meanwhile, the spoke-type permanent magnet (PM) structure is designed to cope with the reduced armature slot area...
The two-individual current control loops and vector space decomposition (VSD) control for a dual 3-phase PMSM are compared and investigated in this paper. It is found that the VSD control has more flexibility on controlling the fundamental current in αβ sub-plane and the fifth, seventh current harmonics in z1Z2 sub-plane with different PI gains, while the two-individual current control is equivalent...
The current control of asymmetric PM synchronous machine is investigated systematically in this paper. The conventional proportional-integral (PI) control in dq-frame and three typical balanced current control methods are investigated and their relationship is revealed. These three methods include the proportional and resonant (PR) control in stationary αβ-frame, the dual current control, and the...
In this paper, a novel variable-mode partitioned stator switched flux memory machine (PS-SFMM) with spoke-type low coercive force (LCF) permanent magnets (PMs) is developed. Due to the changeable magnetization level and polarity of LCF PMs, the PM pole number within inner stator can be purposely varied to either 12 or 6. Thus, this pole-changing concept enables PS-SFMM to behave similarly as 12-pole...
In this paper, novel dual stator switched flux hybrid magnet machines (DS-SF-HMMM) are proposed. Two sets of armature winding are employed so as to improve the space utilization ratio and torque density. Whereas, two kinds of permanent magnets (PMs), i.e., NdFeB and low coercive force (LCF) magnets are placed on either a single stator or two separate stators. The proposed machines can provide the...
This paper comprehensively investigates the voltage distortion (i.e. terminal voltage ripple) mechanisms in surface-mounted permanent magnet (SPM) machines equipped with a single layer fractional slot concentrated winding (FSCW). Stator flux gaps can be used in FSCW machines to increase the pitch factor and hence the winding factor, as well as to simplify the manufacturing process. Furthermore, they...
Rotor bar current of an induction machine (IM) designed by using the same stator outer diameter, stack length, air-gap length, output power and rated speed as the Toyota Prius 2010 interior permanent magnet machine is investigated. It is observed that in some cases the rotor bar current waveform can be non-sinusoidal even if the stator windings are fed with a sinusoidal source. The conditions for...
In order to minimize the cogging torque and torque ripple for surface mounted permanent magnet (SPM) machines, this paper proposes a C-core modular stator which can be obtained by inserting flux gaps (FGs) into every stator tooth. The electromagnetic performances of C-core modular PM machines such as open-circuit flux linkage, phase back-EMF, cogging torque and torque ripple, etc. are comprehensively...
In this paper, electromagnetic performances of twelve-phase 24-stator-slot redundant switched flux permanent magnet (SFPM) machines with 20-, 22-, 26- and 28-rotor-pole rotors are analyzed. The influences of key design parameters on the open-circuit electro-motive-force (EMF) and cogging torque are comparatively evaluated by 2D finite-element analysis (FEA). FEA results show that the 24/26 SFPM machine...
This paper investigates the influence of magnetic saturation on the rotor bar current waveform and performance characteristics of a squirrel-cage Induction Machine (IM). The levels of iron saturation in different parts, including stator and rotor back iron, tooth body and tooth tips etc., are examined and their influences are investigated, while the dominant part which causes the non-sinusoidal rotor...
Wind power turbines have shown a significant increase in the energy production capabilities in recent years. For better reliability and higher efficiency, the direct drive permanent magnet (PM) generators become more desirable, particularly for off-shore wind turbines. This results in generators with large diameter and high pole pair number. To investigate the influence of manufacturing tolerances...
This paper proposes a method for enhancing torque capability of a dual 3-phase permanent magnet synchronous machine (PMSM) drive system by injecting the fifth and seventh current harmonics without any hardware reconfiguration. In this approach, compared with the third current harmonic injection which is commonly used to enhance torque capability, the two isolated neutral points of the dual 3-phase...
In this paper, the investigation is focused on the influence of tooth-tip local magnetic saturation on the on-load performances, such as on-load flux linkages, inductances, onload back EMFs, on-load cogging torques, torque ripples, iron and PM eddy current losses, in a closed-slot fractional slot surface-mount machine. It is found that due to influence of local magnetic saturation in the tooth-tips,...
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