Ripple Loss Research Articles

Design and analysis of a new partitioned stator flux‐modulation motor for direct drive applications

In this study, in order to improve the torque density of the conventional permanent magnet (PM) motor, a flux-modulation (FM) motor employing the magnetic gear effect is proposed. However, the FM motor has space conflict in the finite stator area, which limits the further improvement of torque density. Therefore, a new partitioned stator flux-modulation (PSFM) motor with separated PM excitation and armature windings is artfully proposed. The main design parameters influence on the average electromagnetic torque in the proposed PSFM motor is investigated, together with the proposed FM motor. Furthermore, based on the optimal designs for the highest average electromagnetic torque in this study, the electromagnetic performances of the three motors, including back-electromotive force performances, torque characteristics and several other performances with respect to speed are analysed by finite-element method. Additionally in the PSFM motor, torque generation mechanism and the reduction method of torque ripple are theoretically analysed. Results show that the proposed PSFM motor exhibits 29.1% higher torque density than the FM motor and 87.6% higher than the conventional PM motor with reduced torque ripple and superior loss performance. Finally, the proposed PSFM motor is prototyped for verification.

A Novel PMSM with Optimized Asymmetric Eccentric Air-Gap for High-Power Electric Motorcycle

In order to improve power density of high-power electric motorcycle driving motor, the air-gap length is usually minimized, which aggravates the influence of armature reaction on air-gap magnetic field. Considering the fact of unidirectional driving of electric motorcycle, the eccentric air-gap is used in each pole air-gap magnetic field strengthened area to suppress armature reaction, thus an asymmetric eccentric air-gap structure is designed. The torque and efficiency of motor are improved by asymmetric structure optimizing to improve the comfort, load capacity and battery life of vehicle, the ratio of maximum air-gap to minimum air-gap is eventually determined to be 3.2. The results of simulation and experiment show that, for the specified rotation direction, the distortion of air-gap magnetic density and back electromotive force (back-EMF) caused by armature reaction can be significantly suppressed by the determined asymmetric structure, hence the torque ripple and iron loss are reduced by 70.66% and 20.9% under rated load, respectively. Meanwhile, the proposed motor can provide a wide speed range and superior speed control performance, thus, verifying the validity and feasibility of the proposed asymmetric eccentric air-gap structure.

Conceptual Design of Fractional Slot Concentrated Winding Dual-Rotor Double-Speed Synchronous Motor

Fractional slot concentrated winding (FSCW) permanent magnet (PM) motors are becoming an attractive solution in low-speed applications due to their superior advantages. A new topology of FSCW motor is introduced in this article, which consist of single stator and two PM rotors with different and opposite direction rated speed. The stator torque reaction is reduced significantly due to the opposite rotational direction of rotors. Some performance characteristics of proposed topology are investigated by designing and manufacturing a 0.5 kW prototype motor. The back-emf voltages, torque reaction, torque ripple and core losses are obtained via finite elements method (FEM) and are compared with two conventional FSCW motors. The prototypes of case-studied motors are tested experimentally in order to validate the advantages of proposed motor.

Design and optimization of HTS flux-switching permanent magnet machine

<p>Flux-switching permanent magnet (FSPM) machine with high temperature superconductors (HTS) bulks located between the rotor poles to eliminate the flux leakage in the rotor, termed as (HTS-FSPM) machine has been proposed in this paper. Using genetic algorithm, the HTS and the conventional FSPM machines having the same size constraints and load conditions have been globally optimized for max. aveage torque. To highlight the advantages of the HTS-FSPM machine, a performance comparison between the conventional and HTS-FSPM machines has been presented. It is found that the HTS-FSPM machine can increase the torque by 27%, however, this comes with the expense of higher torque ripple and power losses. </p>

Fault-Tolerant Operation Under Single-Phase Open in Mono Inverter Dual Parallel SMPMSM With Single Shaft

This paper presents a fault-tolerant operation for dual three-phase surface-mounted permanent magnet machines (SPMSMs) that were both electrically connected on three winding phases and mechanically connected on one shaft. The open-phase fault-tolerant operation is considered in dual three-phase SPMSMs drive thus combining motor drive of three-phase and single-phase. The proposed method controls the torque of each motor with different phases using a single inverter. In order to control these motors, the torque and current are distributed between the motors with the specific ratio. Methods for minimizing torque ripple and copper losses and maximizing the output torque of the three-phase motor are stated in this paper. Accordingly, a system with cost-effective and enhanced reliability is proposed without any configuration adjustment or auxiliary switching devices. The mathematical analysis and experiments are presented to verify the feasibility of the proposed method. After the fault, the resulting system is able to provide up to 75% of the rated torque, and up to 50% of the torque can be utilized without any torque ripple.

Wideband Hybrid Envelope Tracking Modulator With Hysteretic-Controlled Three-Level Switching Converter and Slew-Rate Enhanced Linear Amplifier

A wideband hybrid Envelope tracking (ET) modulator utilizing a hysteretic-controlled three-level switching converter (3L-SWC) and a slew-rate enhanced linear amplifier (LA) are presented. In addition to smaller ripple and lower losses of 3L-SWCs, employing the proposed hysteresis control loop results in a higher speed loop and wider bandwidth converter, enabling over 80 MHz of switching frequency. A concurrent sensor circuit monitors and regulates the flying capacitor voltage $V_{\mathrm{ CF}}$ and eliminates the conventionally required calibration loop to control it. The hysteretic-controlled 3L-SWC provides a high percentage of power amplifier (PA) supply load current with lower ripple, reducing the LA high-frequency current and ripple cancellation current, improving the overall system efficiency. A slew-rate enhancement (SRE) circuit is employed in the LA, resulting in slew rate of over 307 V/ $\mu \text{s}$ and bandwidth of over 275 MHz for the LA. The SRE circuit provides a parallel auxiliary current path directly to the gate of the class-AB output stage transistors, speeding-up the charging or discharging of output without modifying the operating point of the remaining LA, while maintaining the quiescent current of the class-AB stage. The supply modulator is fabricated in a 65-nm CMOS process. The measurement results show the tracking of long-term evolution (LTE)-40-MHz envelope with 93% peak efficiency at 1-W output power, while the SRE is disabled. Enabling the SRE, it can track LTE-80-MHz envelope with peak efficiency of 91%.

Novel Current Profile of Switched Reluctance Machines for Torque Density Enhancement in Low-Speed Applications

In this article, a current profiling technique is proposed for the torque density enhancement in switched reluctance machines (SRMs). The novel current profile is initially developed from the harmonic current injection method and is then modified into a unipolar waveform to allow the application of an asymmetric bridge inverter. It is found that, neglecting the magnetic saturation, the optimal current profile for the maximum torque per ampere operation in an SRM is close to a pulse with high-order harmonics. However, an optimized current with relatively low-order harmonics can provide better performance in the practical situation. Based on the analytical and the finite element results, the proposed method is proved to be able to enhance the torque density by 20% at the light load condition and by 15% at the rated condition compared with the conventional SRM excitation. Also, the large torque ripple and core loss in SRMs are suppressed and the efficiency is improved. More importantly, unlike many other current profiling techniques, the proposed current profile has fixed parameters and is easily adaptable to different machine specifications. The effectiveness of the proposed method is verified by both the finite-element analyses and the experiments.

A Simple and Efficient Quasi-3D Magnetic Equivalent Circuit for Surface Axial Flux Permanent Magnet Synchronous Machines

This paper presents a simple and efficient magnetic equivalent circuit (MEC) model for surface axial flux permanent magnet synchronous machines. The MEC model is used to solve all the electromagnetic properties of the machine including the no load, full load voltages, cogging torque, torque ripple, and stator iron core losses. Moreover, this approach can be extended for all surface permanent magnet synchronous machines. The main novelty of this approach is the development of a static system, which accounts for the rotation. The model takes into account the rotor rotation via time-dependent permanent magnet magnetization sources. The static system matrix facilitates a very fast solving. In addition, to take into account the three-dimensional (3-D) effect, a multislicing of the machine in the radial direction is done. This boosts the simulation time to only 60 s for six slices and 50 time steps including the nonlinear behavior of the stator elements with a great accuracy. Additionally, the number of elements in the MEC can be adjusted to reduce the computational time. This model is verified by means of 3-D and two-dimensional (2-D) multislice finite-element models. In addition, experimental validations are also provided at the end.

Development of a Four-Switch Buck-Boost Converter: Operation Modes, Control and Experimental Results

This paper presents the development and practical implementation of a four-switch buck-boost converter for variable input voltage. The circuit operates in buck or boost mode when the input values are higher or lower than the output. For voltages near the required level, the traditional buck-boost mode is replaced by modes A and B consisting in the combination of some periods working in buck mode with others working in boost mode. The sequence and duty cycle assignment of these transition modes are defined according to an approach based on steady-state analysis and discrete-time models. The digital system is completed by the addition of a voltage control loop that regulates the output under possible perturbations. Experimental results show that the proposed modes A and B present less ripple and appreciable less losses than the buck-boost counterpart. Thus, the prototype achieves efficiencies above 95% for all the input range and nominal load.

Advanced Rectifier Topology with Variable Speed High Power PMSG Wind Turbine with Filter Scheme

Advance rectifier topology consisting of two three phase diode bridges and three thyristors is proposed in the paper for variable-speed high-power permanent-magnet synchronous generator (PMSG) wind energy conversion systems (WECSs) by using filter in addition. The recommended advanced rectifier has such as simplicity, low cost and low loss. Its feature to cascade the input voltage allows it to properly manage generator speed even when the wind velocity sink to half of the rated value. This feature is identical to a voltage boost function that cannot be found in conventional diode or thyristor rectifiers. Due to nature of a diode–thyristor rectifier, it generates harmonic currents. Also the resultant torque ripple and harmonic loss in the generators are also higher. In this we alleviated this problem by adding filters which is also verified by simulation result. Consequently, maximum power-point-tracking algorithms can be applied to optimize power capture in a wide range of wind velocities. The operating principle of the rectifier is elaborated. Its use and control in the WECS is presented.

Improved Direct Resonant Control for Suppressing Torque Ripple and Reducing Harmonic Current Losses of DFIG-DC System

The most prominent problem of the doubly fed induction generator-dc (DFIG-dc) system is the highly distorted stator voltage due to the diode bridge on stator side. The highly distorted stator voltage not only influences the stator voltage orientation control but also causes harmonic currents and torque ripples. In this paper, an enhanced stator fundamental voltage orientation method is proposed to deal with the highly distorted stator voltage. Furthermore, the relationship between torque ripples and harmonic currents is investigated. And then an improved direct resonant control strategy is proposed for suppressing the torque ripple and reducing the harmonic currents simultaneously. In this way, the loss of harmonic currents can be reduced while suppressing the torque ripple. Finally, the experimental results are presented to validate the effectiveness of the proposed control strategy.

Performance evaluation of electric vehicle brushless direct current motor with a novel high-performance control strategy with experimental implementation

In this article, a new control strategy for electric vehicle battery autonomy and performance improvements is proposed. This method is based on the use of a DC-DC converter combined with a brushless DC motor as an electric vehicle propulsion engine. First, an analysis of the three-phase brushless DC motor performance based on analytical modeling is addressed. This model stands on the derivative of the commutated and non-commutated phase currents from which the speed response is induced. The proposed model presents different brushless DC motor pulse width modulation control modes and allows highlighting the most appropriate mode with lower current ripple and power loss, higher efficiency and faster response. Furthermore, a DC-DC boost converter is integrated in the motor control scheme, to describe after, how the electric vehicle performance is increased when implementing this control mode. Evaluation of the analytic results has been validated through simulations on MATLAB/Simulink. The evaluation focuses on speed response for different pulse width modulation control modes, current ripple rate in addition to the electric vehicle performance with and without DC-DC converter. In addition, an experimental validation using a laboratory designed platform is performed. The proposed method demonstrates a better electric vehicle performance in terms of increasing the battery autonomy and speed range.

Research on the Influences of Time Harmonics on Permanent Magnet Synchronous Motors with Hybrid Magnet Poles

With the development of electric electron technology and controlling technology, controller for driving permanent magnet synchronous motors is used widely. The using of a controller can expand the motor speed range and improve motor runtime performances. However, the output current of a controller contains lots of time harmonics that will have bad influences on motor torque and losses. In order to analyze the influences of the time harmonics on the motor performances, different time harmonic currents were injected into the motor armature. Taking a 750 W, 250 r/min permanent magnet synchronous motor with hybrid magnet poles (HPPMSM) as an example, the 2-D finite model was established. On this basis, the torque ripple and eddy current losses of permanent magnets with different time harmonics were obtained. The influences of time harmonics on motor torque ripple and eddy current losses were determined, and the impacting mechanism was revealed. The analyses may be helpful for the optimal design of HPPMSM.

Analysis and Reduction of Stator Copper Losses in Three-phase Four-switching Inverter-fed SPMSM Drives Using Space Vector Pulse-width Modulation

In consideration of cost reduction, three-phase four-switch (TPFS) converters are applied in permanent magnet synchronous motor/generator (PMSM/G) drive application. However, the reduced number of active vectors has a negative influence on the signal waveform and the stator copper losses. With respect to the stator copper loss reduction, the root-mean-square (RMS) value of the stator copper loss ripple is chosen as a performance criterion in this paper. It is proved in this paper that the stator current ripple plays a more important role than the equivalent resistance in the copper loss ripples by double Fourier integral analysis. Thus, the RMS value of the stator current ripple can be applied as an analytical approach to evaluate the stator harmonic copper losses of the two proposed space vector modulation (SVM). Consequently, the proposed SVM strategy realizes the high-frequency stator copper loss ripple reduction. The experimental results demonstrate the validation of the proposed analysis.

Photosensitive Glass-Ceramics for Heterogeneous Integration

The push for heterogeneous integration requires very unique material properties with respect to processing, material constants, and integration capabilities with other materials (such as copper, II...

Space Harmonics Elimination for Fractional-Slot Windings With Two-Slot Coil Pitch

Recently, fractional-slot windings with two-slot coil pitch are receiving more and more attention due to their lower space harmonic contents in stator magnetomotive force (MMF) compared with the widely-used fractional-slot nonoverlapping counterparts. To further reduce the detrimental space harmonics for this type of winding, various solutions featured by varied coil turn ratios are investigated in this paper. Firstly, all the feasible slot and pole number combinations for fractional-slot windings with two-slot coil pitch are discussed. Secondly, two types of Slot Harmonic Only Windings (SHOW), i.e., SHOW I and SHOW II, are illustrated on the 18-slot/10-pole (18S10P) and 24S10P windings, through which only the main harmonic and its slot harmonics will be present in stator MMF harmonics. Then, to overcome the drawback of reduced main harmonic magnitude owing to both the decreased winding factor and poor slot area utilization associated with the SHOW, two solutions, i.e., 6-0 solution and 5-1 solution for 18S10P and four alternatives, i.e., 7-1 solution, 6-2 solution, 5-3 solution and 4-4 solution for 24S10P, are proposed based on the SHOW I or SHOW II. It is found that the 5-1 solution for 18S10P and 5-3 solution for 24S10P winding are the most desirable ones considering the tradeoff between larger main harmonic magnitude and lower harmonic contents. Furthermore, electromagnetic performance comparisons are carried out between 24S10P permanent magnet (PM) machines with 5-3 solution and 12S10 two layer and 24S10P two layer machines. Although the average torque of the 24S10P machine with 5-3 solution has a slight decrease, its torque ripple and radial magnetic force density rotor eddy-current losses are greatly suppressed compared with the two layer counterparts.

Integrated Assessment of Economic Losses in Manufacturing Industry in Shanghai Metropolitan Area Under an Extreme Storm Flood Scenario

In this paper, we developed an integrated methodology for assessing asset damage, production capacity loss, and inter-sector ripple loss using the depth-damage curve, Cobb-Douglas production function and Input-Output model. We applied this methodology to the detailed individual manufacturing firms in Shanghai under an extreme storm floods scenario to simulate the disaster impact propagation from local individual firms to the entire industrial system and comprehensively estimate the resulting economic losses and their spatial distribution. Our results show that given no floodwall protection, a 1000-year storm flood scenario would cause direct asset damage of US $21 billion to the Shanghai manufacturing industry, including fixed asset damage of US $12 billion and inventory damage of US $9 billion. Due to the shortage of input productive factors of asset and labor, it would further lead to production capacity loss of US $24 billion. In addition, affected manufacturing industry would indirectly result in ripple loss of US $60 billion among dependent sectors, which has a significant amplifier effect. Our results have important implications for reasonable cost-benefit analysis of structural flood control measures in coastal areas, as well as for manufacturing firm location planning and resilience strategy decision-making.

Torque Ripple Reduction for Switched Reluctance Motor with Optimized PWM Control Strategy

The high current ripple and torque ripple are the main drawbacks of the switched reluctance motor (SRM) since the nonlinearity and double saliency, which limits its applications. In order to eliminate the current variation and torque ripple, an optimized pulse width modulation (PWM) control is presented in this paper. The voltage ratio duty is able to be predicted precisely according to the information of the motor running parameter. Based on torque sharing functions (TSFs), the current profile is pre-computed and four regions are defined according to the reference current profiles. The three modes, excitation, demagnetization and freewheeling, are flexibly chosen according to the characteristic of the current profile. It is indicated that it is better than that of conventional PWM modulation in terms of current ripple and the current tracing performance is improved without increasing the switching frequency or changing the hysteresis band. The current ripple is defined as the peak-to-peak value dividing the average value and it is reduced by 40%. A comparison in terms of the torque ripple and copper loss is also carried out: the torque ripple is significantly reduced via the proposed scheme under both magnetic linear and saturation conditions. The torque ripple and copper loss are reduced by about 70% and 12%, respectively. The validity and effectiveness of the proposed control strategy is verified by simulation and experimental results.

Electromagnetic Performance Comparison of Multi-Layered Interior Permanent Magnet Machines for EV Traction Applications

Electromagnetic performance of three multi-layered interior permanent magnet (IPM) machines are investigated and compared for electric vehicle applications in this paper. The rotor structure, air-gap field distribution, torque density, torque ripple, core loss, magnet eddy-current loss, and output power are studied with finite-element analysis. It is demonstrated that the two-layered rotor structure with magnets buried deeply has the lower torque density and magnet eddy-current loss due to the utilization of magnets and the block effects of the armature-reaction flux is lower. The three-layered IPM machine has the lower torque ripple and core loss than two-layered IPM machines because the harmonics of air-gap density are reduce by the increase of magnet layers. Finally, an IPM machine with three-layered magnets rotor is prototyped to verify the analysis.

Ripple modifications to alpha transport in tokamaks

Magnetic field ripple is inherent in tokamaks since the toroidal magnetic field is generated by a finite number of toroidal field coils. The field ripple results in departures from axisymmetry that cause radial transport losses of particles and heat. These ripple losses are a serious concern for alphas near their birth speed $v_{0}$ since alpha heating of the background plasma is required to make fusion reactors into economical power plants. Ripple in tokamaks gives rise to at least two alpha transport regimes of concern. As the slowing down time $\unicode[STIX]{x1D70F}_{s}$ is much larger than the time for an alpha just born to make a toroidal transit, a regime referred to as the $1/\unicode[STIX]{x1D708}\propto \unicode[STIX]{x1D70F}_{s}$ regime can be encountered, with $\unicode[STIX]{x1D708}$ the appropriate alpha collision frequency. In this regime the radial transport losses increase as $v_{0}\unicode[STIX]{x1D70F}_{s}/R$, with $R$ the major radius of the tokamak. The deleterious effect of ripple transport is mitigated by electric and magnetic drifts within the flux surface. When drift tangent to the flux surface becomes significant another ripple regime, referred to as the $\sqrt{\unicode[STIX]{x1D708}}$ regime, is encountered where a collisional boundary layer due to the drift plays a key role. We evaluate the alpha transport in both regimes, taking account of the alphas having a slowing down rather than a Maxwellian distribution function and their being collisionally scattered by a collision operator appropriate for alphas. Alpha ripple transport is found to be in the $\sqrt{\unicode[STIX]{x1D708}}$ regime where it will be a serious issue for typical tokamak reactors as it will be well above the axisymmetric neoclassical level and can be large enough to deplete the alpha slowing down distribution function unless toroidal rotation is strong.