Search Results (18)

In this paper, the effects of asymmetric interior permanent magnet (AIPM) rotors on the torque characteristics in dual three-phase (DTP) permanent magnet synchronous machines (PMSMs) are investigated. The electromagnetic performances of DTP PMSMs with symmetrical and asymmetric IPM rotors are compared, including air-gap flux density, back EMF, cogging torque, torque, loss, and efficiency. It is found that in DTP PMSMs, the AIPM rotor can achieve significant torque improvement under both healthy and single three-phase open-circuit conditions. It is also found that performance enhancement in AIPM DTP machines is more remarkable across the constant torque region, particularly at high-load conditions, than in the constant power region, compared with the symmetrical IPM counterpart. A prototype is fabricated and tested to verify theoretical analyses. Full article

In this paper, a method for determining the optimal stator-rotor combinations of conventional flux-switching permanent magnet (FSPM) machines with composite phase numbers covering symmetrical and asymmetrical topologies is proposed by changing the equivalent number of coils per pole per phase (ENCPP) or the number of coil-pairs having complementarity (K) of the optimal stator-rotor combinations of the corresponding machines with prime phases. Taking composite phase machines such as four-phase, six-phase, nine-phase, and twelve-phase machines as examples, a detailed analysis is conducted on how the optimal stator-rotor combinations of four-phase machines are derived from the optimal stator-rotor combinations of the corresponding prime phase machines (i.e., two-phase machines) and how the optimal stator-rotor combinations of six-phase, nine-phase, and twelve-phase machines are derived from the optimal stator-rotor combinations of the corresponding prime phase machines (i.e., three-phase machines). Then, the winding factor of the conventional FSPM machines with composite phase numbers is calculated. Finally, taking a 24-slot/22-tooth (24/22) conventional FSPM topology as an example, the topology is connected into a standard six-phase machine (symmetrical topology) and a dual three-phase machine (asymmetrical topology), and a comparative study between them is conducted in terms of the phase back electromotive force (EMF) waveform, electromagnetic torque, torque ripple, and inductances. The results indicate that both machines have sufficiently large and symmetrical back-EMFs, as well as sufficiently large electromagnetic torque, which validates the correctness of the proposed method for determining the optimal stator-rotor combinations. Full article

Harmonic distortion caused by phase jumps in the phase-locked loop (PLL) during asymmetric faults poses a significant threat to the secure operation of renewable energy grid-connected systems. A harmonic suppression strategy based on Vague set theory is proposed for offshore wind power AC transmission systems. By employing the three-dimensional membership framework of Vague sets—comprising true, false, and hesitation degrees—phase-locked errors are characterized, and dynamic, real-time PLL proportional-integral (PI) parameters are derived. This approach addresses the inadequacy of harmonic suppression in conventional PLL, where fixed PI parameters limit performance under asymmetric faults. The significance of this research is reflected in the improved power quality of offshore wind power grid integration, the provision of technical solutions supporting efficient clean energy utilization in alignment with “Dual Carbon” objectives, and the introduction of innovative approaches to harmonic suppression in complex grid environments. Firstly, an equivalent circuit model of the offshore wind power AC transmission system is established, and the impact of PLL phase jumps on grid harmonics during asymmetric faults is analyzed in conjunction with PLL locking mechanisms. Secondly, Vague sets are employed to model the phase-locked error interval across three dimensions, enabling adaptive PI parameter tuning to suppress harmonic content during such faults. Finally, time-domain simulations conducted in PSCAD indicate that the proposed Vague set-based control strategy reduces total harmonic distortion (THD) to 1.08%, 1.12%, and 0.97% for single-phase-to-ground, two-phase-to-ground, and two-phase short-circuit faults, respectively. These values correspond to relative reductions of 13.6%, 33.7%, and 80.87% compared to conventional control strategies, thereby confirming the efficacy of the proposed method in minimizing grid-connected harmonic distortions. Full article

Since the 1960s, theorists have claimed that the electroweak force, which unifies parity-conserving electromagnetic and parity-violating weak nuclear forces, induces tiny parity-violating energy differences (10⁻¹⁰–10⁻²¹ eV) between mirror-image molecules. This study reports the dual mirror-symmetry-breaking and second-order phase transition characteristics of mirror-symmetric 7₃-helical poly(di-n-butylsilane) in n-alkanes under static (non-stirring) conditions. In particular, n-dodecane-h₂₆ significantly enhances the circular dichroism (CD) and circularly polarized luminescence (CPL) spectra. A new (−)-CD band emerges at 299 nm below T_C1 ~ 105 °C, with a helix–helix transition at T_C2 ~ 28 °C, and exhibits g_abs = +1.3 × 10⁻² at −10 °C. Synchronously, the CPL band at 340 nm exhibiting g_lum = −0.7 × 10⁻² at 60 °C inverts to g_lum = +2.0 × 10⁻² at 0 °C. Interestingly, clockwise and counterclockwise stirring of the mixture induced non-mirror-image CD spectra. n-Dodecane-d₂₆ weakens the g_abs values by an order of magnitude, and oppositely signed CD and a lower T_C1 of ~45 °C are observed. The notable H/D isotope effect suggests that the CH₃ termini of the polysilane and n-dodecane-h₂₆, which comprise a three identical nuclear spin-1/2 system in a triple-well potential, effectively work as unidirectional hindered rotors due to the handedness of nuclear-spin-dependent parity-violating universal forces. This is supported by the (−)-sign vibrational CD bands in the symmetric and asymmetric bending modes of the CH₃ group in n-dodecane-h₂₆. Full article

We propose two types of structures to achieve the control of Fano and electromagnetically induced transparency (EIT) line shapes, in which dual one-dimensional (1D) photonic crystal nanobeam cavities (PCNCs) are side-coupled to a bus waveguide with different gaps. For the proposed type Ⅰ and type Ⅱ systems, the phase differences between the nanobeam periodic structures of the two cavities are π and 0, respectively. The whole structures are theoretically analyzed via the coupled mode theory and numerically demonstrated using the three-dimensional finite-difference time-domain (3D FDTD) method. The simulation results show that the proposed structure can achieve several kinds of spectra, including Fano, EIT and asymmetric EIT line shapes, which is dependent on the width of the bus waveguide. Compared to the previously proposed Fano resonator with 1D PCNCs, the proposed structures have the advantages of high transmission at the resonant peak, low insertion loss at non-resonant wavelengths, a wide free spectral range (FSR) and a high roll-off rate. Therefore, we believe the proposed structure can find broad applications in optical switches, modulators and sensors. Full article

A modular approach to the construction of electric machines, drive systems, power supply systems is a new direction of modern technology development. Especially, the modular approach is promising for electric vehicles due to such positive aspects as increased efficiency, fault tolerance, overall reliability, safety, enhanced control capabilities, etc. In this work, the modular approach is comprehensively applied to an EV powertrain system, which includes a dual three-phase (DTP) BLDC motor with two machine modules of an asymmetric configuration, two battery modules and a supercapacitor module (SCM). The proposed H–H configuration of modular EV powertrain system includes four voltage source inverters that combine the power modules with the open ends of the windings (OEW) of the module machine armature, and provide control of their operation. Based on the developed mode system of the OEW machine module operation for EV traction and braking, a general control algorithm for the proposed configuration of the modular EV powertrain system has been developed. It combines the control of the operating modes with the functions of maintaining the required SOC level of the SCM and equalizing the SOCs of the two battery modules. The conducted simulation and experimental studies confirmed the workability and effectiveness of the proposed solutions. Full article

The DC-Link capacitor plays a crucial role as far as power density and reliability are concerned: it occupies approximately 40% of the inverter, and causes approximately 30% of its failures. Asymmetrical dual three-phase (ADTP) multiphase arrangements are gaining relevance in the automotive sector for powertrain applications. This work focuses on reducing the impact that the widely used double zero sequence injection (DZSI) family of PWM techniques have on such a bulky and failure-prone component in an ADTP arrangement by means of interleaving techniques. By using the double Fourier integral formalism, the input current spectra and the overall performance of these PWM techniques have been derived, in terms of current rms value and voltage ripple in the DC-Link capacitor. Simulations have shown that choosing an adequate interleaving scheme and angle considerably relieves both current and voltage stresses on the DC-Link capacitor compared to noninterleaved operation. Reductions of 84% current rms and 86% voltage ripple have been achieved at static operating points. Finally, by averaging the rms current over WLTP standard driving cycle, reductions up to 26% have been obtained under more realistic conditions. All this would enhance the reliability and reduce the size of the onboard capacitors in future electric vehicles. Full article

As the oil and petrochemical products pass through the oil pipeline, the sediment scale settles, which can cause many problems in the oil fields. Timely detection of the scale inside the pipes and taking action to solve it prevents problems such as a decrease in the efficiency of oil equipment, the wastage of energy, and the increase in repair costs. In this research, an accurate detection system of the scale thickness has been introduced, which its performance is based on the attenuation of gamma rays. The detection system consists of a dual-energy gamma source (²⁴¹ Am and ¹³³ Ba radioisotopes) and a sodium iodide detector. This detection system is placed on both sides of a test pipe, which is used to simulate a three-phase flow in the stratified regime. The three-phase flow includes water, gas, and oil, which have been investigated in different volume percentages. An asymmetrical scale inside the pipe, made of barium sulfate, is simulated in different thicknesses. After irradiating the gamma-ray to the test pipe and receiving the intensity of the photons by the detector, time characteristics with the names of sample SSR, sample mean, sample skewness, and sample kurtosis were extracted from the received signal, and they were introduced as the inputs of a GMDH neural network. The neural network was able to predict the scale thickness value with an RMSE of less than 0.2, which is a very low error compared to previous research. In addition, the feature extraction technique made it possible to predict the scale value with high accuracy using only one detector. Full article

A common-mode voltage (CMV) suppression strategy, namely double zero-sequence injection common-mode voltage (DZICMV), is proposed in this paper for an asymmetrical six-phase induction motor fed by two-level dual three-phase voltage source inverters (VSIs). In this strategy, the sinusoidal waveforms injected by double zero-sequence signals are employed as modulation signals, and two opposite triangular waveforms are used as carriers. The fundamental period is divided into 24 sectors. In each sector, the carrier used by the medium amplitude phase is distinct from the carriers used by the other two phases in each set of three-phase windings. Using this method, the zero vectors (000) and (111) in each set of three-phase windings can be eliminated, and the peak values of sub-CMV and total CMV can be reduced from ±U_dc/2 to ±U_dc/6. The experiment results show that the root mean square (RMS) value of common-mode leakage current in DZICMV can be reduced by 51.83% compared with the double zero-sequence injection PWM (DZIPWM) strategy. It is also found in the other four existing benchmark CMV suppression strategies that the peak values of sub-CMV therein are nearly all ±U_dc/2, and only in the low linear modulation region could one of these strategies suppress sub-CMV peak values to ±U_dc/6. However, the proposed DZICMV can suppress the sub-CMV peak values to ±U_dc/6 in the whole linear modulation range. Moreover, the maximum linear modulation index of the DZICMV is 1.15, which is larger than that of the four benchmark strategies, whose maximum modulation index is 1. Full article

Dual three-phase permanent-magnet synchronous motors (PMSM) have wide applications in electric vehicles due to advantages such as excellent control performance and outstanding fault tolerance capability. However, present fault-tolerant control of inverter single-leg open-circuit faults cannot make full use of each phase winding of the motor, which limits the torque-production capability. This paper proposes a torque superposition compensation (TSC) control which can minimize the stator copper losses while increasing the torque-production capability. The phase winding originally connected to the faulty inverter leg is then linked to the DC-link mid-point. Thus, the winding in the faulty phase can be utilized to generate an additional torque. The symmetric dual three-phase windings torque model and the asymmetric five-phase windings compensation torque model for U_d/2 voltage level are constructed according to the torque superposition, respectively. Then, the three-subplane decomposition transformation matrix for the post-fault dual three-phase PMSM is derived, and the decoupling model in the d-q subplane is constructed, which achieves the optimal enhancement of the torque-production capability. The simulation results verify the effectiveness of the proposed TSC fault-tolerant control. Full article

We report feedback-induced frequency oscillations using a power-split-ratio through asymmetric dual-loop optical feedback (Loop I: ~2.2 km and Loop II: ~20 m) subject to a self-mode-locked two-section QDash laser emitting at 1550 nm and operating at 21 GHz repetition rate. To assess the suppression of frequency resonances, three chosen combinations of feedback power (Loop I: −27.27 dB and Loop II: −19.74 dB, Loop I: −22 dB and Loop II: −22 dB, and Loop I: −19.74 dB and Loop II: −27.27 dB) through asymmetric dual-loop optical feedback have been studied. Based on the chosen coupling strength, an optimum feedback ratio that yields better side-mode suppression has been identified. Our results demonstrate that side-mode suppression can be achieved by the fine adjustment of coupling power through either cavity of dual-loop feedback configurations. Furthermore, we have further demonstrated that frequency fluctuations from the RF spectra can be filtered by carefully selecting the delay phase of the second cavity. Our experimental findings suggest that semiconductor mode-locked lasers based on dual-loop feedback configurations can be used to develop noise oscillations free from integrated photonic oscillators for potential applications in telecommunications, multiplexing, and frequency-comb generation. Full article

Electric vehicle charging technology has recently witnessed massive developments due to its significant role in the ever-growing number of electric vehicles on the market. The integrated on-board charger technology (IOBC) represents an effective and attractive solution to reduce EV size, cost, and weight. IOBC technology employs propulsion components, such as the motor and its converter, in the charging process. The main objective of IOBC is to achieve the maximum charging current with zero average/pulsating torque so that mechanical interlocking can be dispensed. Recently, some of the IOBC topologies have adopted machines with six-phase stators to exploit the many advantages of multiphase-based systems. This paper investigates the effect of the winding design, namely, chorded or un-chorded designs, as well as the winding configuration, namely, dual three-phase, asymmetrical, or symmetrical winding configurations, on the current quality of a six-phase-based non-isolated IOBC. The relation between the winding design and the induced low order harmonics in the charging current is first clarified. The required current controller structure is then proposed, which ensures balanced grid line currents with high quality, under either healthy or one-phase fault conditions. Finally, a comparative study between all available designs with the proposed current controller is carried out to validate the theoretical findings. Full article

This paper investigated an electromagnetic torque ripple level of BLDC drives with multiple three-phase (TP) permanent magnet (PM) motors for electric vehicles. For this purpose, mathematical models of PM machines of different armature winding sets-single (STP), dual (DTP), triple (TTP), and quadruple (QTP) ones of asymmetrical configuration and optimal angular displacement between winding sets were developed and corresponding computer models in the Matlab/Simulink environment were created. In conducted simulation, the influence of various factors on the electromagnetic torque ripple of the multiple-TP BLDC drives was investigated—degree of modularity, magnetic coupling between armature winding sets, and drive operation in open and closed-loop control systems. Studies have shown an increase of the electromagnetic torque ripple generated by one module in the multiple TP BLDC drives with magnetically coupled winding sets, due to additional current pulsations caused by magnetic interactions between the machine modules. However, the total electromagnetic torque ripples are much lower than in similar drives with magnetically insulated winding sets. Compared with the STP BLDC drive, the multiple TP BLDC drives with the same output parameters showed a reduction of the electromagnetic torque ripple by 27.6% for the DTP, 32.3% for the TTP, and 34.0% for the QTP BLDC drive. Full article

In this review, we discuss the physical characteristics of the magnetic dual chiral density wave (MDCDW) phase of dense quark matter and argue why it is a promising candidate for the interior matter phase of neutron stars. The MDCDW condensate occurs in the presence of a magnetic field. It is a single-modulated chiral density wave characterized by two dynamically generated parameters: the fermion quasiparticle mass m and the condensate spatial modulation q. The lowest-Landau-level quasiparticle modes in the MDCDW system are asymmetric about the zero energy, a fact that leads to the topological properties and anomalous electric transport exhibited by this phase. The topology makes the MDCDW phase robust against thermal phonon fluctuations, and as such, it does not display the Landau–Peierls instability, a staple feature of single-modulated inhomogeneous chiral condensates in three dimensions. The topology is also reflected in the presence of the electromagnetic chiral anomaly in the effective action and in the formation of hybridized propagating modes known as axion-polaritons. Taking into account that one of the axion-polaritons of this quark phase is gapped, we argue how incident $\gamma$-ray photons can be converted into gapped axion-polaritons in the interior of a magnetar star in the MDCDW phase leading the star to collapse, a phenomenon that can serve to explain the so-called missing pulsar problem in the galactic center. Full article

The transition to electric vehicles (EVs) has received global support as initiatives and legislation are introduced in support of a zero-emissions future envisaged for transportation. Integrated on-board battery chargers (OBCs), which exploit the EV drivetrain elements into the charging process, are considered an elegant solution to achieve this widespread adoption of EVs. Surface-mounted permanent-magnet (SPM) machines have emerged as plausible candidates for EV traction due to their nonsalient characteristics and ease of manufacturing. From an electric machine design perspective, parasitic torque ripple and core losses need to be minimized in integrated OBCs during both propulsion and charging modes. The optimal design of EV propulsion motors has been extensively presented in the literature; however, the performance of the optimal traction machine under the charging mode of operation for integrated OBCs has not received much attention in the literature thus far. This paper investigates the optimal design of a six-phase SPM machine employed in an integrated OBC with two possible winding layouts, namely, dual three-phase or asymmetrical six-phase winding arrangements. First, the sizing equation and optimized geometrical parameters of a six-phase 12-slot/10-pole fractional slot concentrated winding (FSCW)-based SPM machine are introduced. Then, variations in the output average torque, parasitic torque ripple, and parasitic core losses with the slot opening width and the PM width-to-pole pitch ratio are further investigated for the two proposed winding layouts under various operation modes. Eventually, the optimally designed machine is simulated using analytical magnetic equivalent circuit (MEC) models. The obtained results are validated using 2D finite element (FE) analysis. Full article