Ripple Loss Research Articles

Toroidal magnetic field ripple and ion orbit loss effects on edge toroidal rotation in J-TEXT Tokamak plasmas

The edge toroidal rotation on J-TEXT is in the counter-current direction and sensitive to electron density and safety factor. During a density ramp-up phase, the initial toroidal rotation in the edge region (e.g. r/a = 0.7–1), having one speed with little radial dependence, evolves to develop a radial profile when the edge density is sufficiently large. The effects of ripple-induced thermal loss on plasma rotation are predicted by neoclassical theory for those discharges, and comparisons with the measurements are performed. The predictions agree well with the measurements over a range of plasma conditions, confirming that using the ripple effect to interpret the phenomenon is appropriate in certain parameter regimes, while in others the neoclassical effects are not sufficient to predict the experimental observations.

Simple overlap angle control strategy for commutation torque ripple minimisation in BLDC motor drive

In this paper, a novel overlap angle controlled Direct Torque Control (DTC) scheme is proposed which strikes the balance between commutation torque ripple and losses. The commutation torque ripple in a Brushless DC (BLDC) motor is mainly due to the effect of commutation on non-commutating phase current and it will be more severe in high power applications. DCT techniques are used to reduce the torque ripple. In comparison to the conventional two-phase conduction Six-Step DTC (SSDTC), the commutation torque ripple is considerably reduced by Twelve-Step DTC (TSDTC) but at the cost of increased inverter and winding losses. The proposed method offers commutation torque ripple minimisation and loss optimization simultaneously by controlling the motor operation in hybrid two- and three-phase conduction. The proposed method basically leads to motor operation in three phase conduction during overlap region and in two phase conduction during non-overlap region. The overlap and non-overlap regions are identified by calculating the commutation interval and suitably scaling it by a factor . The proposed method is validated through experimental results and the effect on commutation torque ripple and drive efficiency are compared with SSDTC and TSDTC experimentally.

Predictive Torque and Rotor Flux Control of a DFIG-DC System for Torque Ripple Compensation and Loss Minimization

The severe torque ripple normally occurring in the doubly fed induction generator dc (DFIG-dc) system can cause premature failure of mechanical components and shorten the life of the drive train. This paper addresses the torque ripple issue by proposing a predictive direct torque control strategy, which delivers at the same time torque ripple suppression and minimization of losses. The existing control algorithms for torque ripple mitigation are mostly based on resonant controllers and repetitive control forcing the compensation signal either through the current chain or directly into the rotor voltage commands. All these techniques lead to structures with multiple controllers whose tuning is not straightforward. Furthermore, they are very sensitive to the operating frequency, making optimized operation with variable frequency highly challenging. Conversely, the proposed algorithm predicts directly the best rotor voltage space vector to minimize torque ripple and track a prescribed rotor flux amplitude to minimize losses, with no current control chain. As confirmed by simulations and experiments, the strategy allows large stator frequency variations as required by the optimal flux command for minimum losses, whilst ensuring effective torque ripple compensation.

Parameter estimation for BLDCM in rescue hoist drive and reduction of torque ripple and winding loss using conditional extremum current model

Brushless dc motor (BLDCM) presents excellent performance in rescue hoist drive because of its high power&torque density. The development of control strategies greatly improve torque ripple and winding loss of BLDCM respectively. However, it is still a challenge to promote comprehensive performance of hoist system such as loss and vibration etc. in the unified control framework. To solve this problem, a comprehensive control strategy of phase current optimization to reduce winding loss and torque ripple simultaneously for BLDCM that utilizing phase current continuous conduction and estimated back-electromotive force (EMF) is proposed. Firstly, with the electromagnetic torque as the constraint, a conditional extremum model of phase current is built to obtain the minimal solution of three-phase reference current. Secondly, considering non-ideal characteristics of the actual back-EMF wave, a sliding-mode observer is designed to estimate the wave online. Experiment results show that under the same load condition, the torque ripple ratio, winding loss and the current harmonics are all lower in proposed strategy than those inconventional two-phase conduction method. Good performance can be achieved by employing the proposed method in non flux-weakening application like the hoisting.

Recent development of reluctance machines with different winding configurations, excitation methods, and machine structures

This paper reviews the performances of some newly developed reluctance machines with different winding configurations, excitation methods, stator and rotor structures, and slot/pole number combinations. Both the double layer conventional (DLC-), double layer mutually-coupled (DLMC), single layer conventional (SLC-), and single layer mutuallycoupled (SLMC-), as well as fully-pitched (FP) winding configurations have been considered for both rectangular wave and sinewave excitations. Different conduction angles such as unipolar120o elec., unipolar/bipolar 180 oelec., bipolar 240 o elec. and bipolar 360oelec. have been adopted and the most appropriate conduction angles have been obtained for the SRMs with different winding configurations. In addition, with appropriate conduction angles, the 12-slot/14-pole SRMs with modular stator structure is found to produce similar average torque, but lower torque ripple and iron loss when compared to non-modular 12-slot/8-pole SRMs. With sinewave excitation, the doubly salient synchronous reluctance machines with the DLMC winding can produce the highest average torque at high currents and achieve the highest peak efficiency as well. In order to compare with the conventional synchronous reluctance machines (SynRMs) having flux barriers inside the rotor, the appropriate rotor topologies to obtain the maximum average torque have been investigated for different winding configurations and slot/pole number combinations. Furthermore, some prototypes have been built with different winding configurations, stator structures, and slot/pole combinations to validate the predictions.

Variance-Based Robust Optimization of a Permanent Magnet Synchronous Machine

This paper focuses on the application of the variance-based global sensitivity analysis for a topology derivative method in order to solve a stochastic nonlinear time-dependent magnetoquasistatic interface problem. To illustrate the approach a permanent magnet synchronous machine has been considered. Our key objective is to provide a robust design of the rotor poles and of the tooth base in a stator for the reduction of the torque ripple and electromagnetic losses, while taking material uncertainties into account. Input variations of material parameters are modeled using the polynomial chaos expansion technique, which is incorporated into the stochastic collocation method in order to provide a response surface model. Additionally, we can benefit from the variance-based sensitivity analysis. This allows us to reduce the dimensionality of the stochastic optimization problems, described by the random-dependent cost functional. Finally, to validate our approach, we provide the two-dimensional simulations and analysis, which confirm the usefulness of the proposed method and yield a novel topology of a permanent magnet synchronous machine.

Electromagnetic Performance Analysis of Interior PM Machines for Electric Vehicle Applications

An interior permanent magnet (IPM) machine with ∇ + U shape rotor topology is proposed and its electromagnetic performance with typical V shape and ∇ shape for electric vehicle (EV) applications are compared. The pole-arc to pole-pitch ratios are optimized to maximize the fundamental air-gap flux density and minimize its total harmonic distortion (THD) of all the three IPM machines by the finite element (FE) method. It can be obtained that ∇ + U shape rotor topology has the lowest THD of the air-gap flux density. The back electromotive force and its THD orders, cogging torque, torque density, torque ripple, d - and q -axis inductances, saliency ratio, and iron loss of three machines are analyzed and compared. It is demonstrated that the ∇ shape IPM machines have the highest average torque, and the torque ripples of the V shape and ∇ shape machines are almost the same. The ∇ + U shape IPM machine has the lowest torque ripple and iron loss with only a little reduction of average torque. Finally, the ∇ + U shape IPM machine is prototyped to verify the results of the FE analysis.

Driver electronics design and control for a total artificial heart linear motor

For any implantable device size and efficiency are critical properties. Thus, a linear motor for a Total Artificial Heart was optimized with focus on driver electronics and control strategies. Hardware requirements were defined from power supply and motor setup. Four full bridges were chosen for the power electronics. Shunt resistors were set up for current measurement. Unipolar and bipolar switching for power electronics control were compared regarding current ripple and power losses. Here, unipolar switching showed smaller current ripple and required less power to create the necessary motor forces. Based on calculations for minimal power losses Lorentz force was distributed to the actor's four coils. The distribution was determined as ratio of effective magnetic flux through each coil, which was captured by a force test rig. Static and dynamic measurements under physiological conditions analyzed interaction of control and hardware and all efficiencies were over 89%. In conclusion, the designed electronics, optimized control strategy and applied current distribution create the required motor force and perform optimal under physiological conditions. The developed driver electronics and control offer optimized size and efficiency for any implantable or portable device with multiple independent motor coils. Graphical Abstract ᅟ.

Improved rotor structures for increasing flux per pole of permanent magnet synchronous motor

This study proposes an improved rotor structure that can increase the flux per pole of a permanent magnet synchronous motor. The air-gap flux density of the improved rotor-type motor is calculated using an equivalent magnetic circuit and compared with the calculation result that is obtained using finite element analysis (FEA). In addition, the no-load fundamental air-gap flux density of the surface-mounted permanent magnet motor, interior permanent magnet motor, spoke-type motor, and improved rotor-type motor are compared using FEA. Changes in the no-load fundamental air-gap flux density according to changes in the rotor diameter and permanent magnet usage are examined for each rotor type. A comparison of the fundamental air-gap flux densities of the five rotor types, including the improved rotor-type conducted using FEA demonstrated that the air-gap flux density of the improved rotor-type was highest. A comparison of the no-load phase back EMF of the five types was conducted after designing them in the four-pole six-slot structure. Each rotor type is applied to 80 W-grade fan motors, and the torque ripple and iron loss are compared. A prototype of the improved rotor-type motor is developed, and the no-load phase back EMF and load test result are verified through experiments.

Experimental and Simulation Research of AC Ripple Losses in a High Temperature Superconductor Tape

Current leads in superconducting magnets are widely adopted for heavy current transmission, and HTS DC cables have great advantages when used as current leads for such purposes. However, as an important parameter of HTS DC cables, AC loss has a strong impact on the stability and operation cost of current leads. In this paper, experiments were conducted to measure AC ripple losses of HTS tapes and HTS cables, and simulations of HTS tapes were carried out. The paper has reached conclusions on the relation between AC losses and power frequencies.

Ignition studies of D-3He spherical tokamak reactor

Ignition access in a neutron lean D-3He fusion reactor is presented using a spherical tokamak (ST). The small central solenoid (CS) or the iron core transformer placed in the center provides the initial plasma current up to 1 ∼ 4 MA, and then the heating power and vertical field ramp up the plasma current up to 100 MA in this proposed D-3He ST reactor. This is operated in the thermally stable low density and high temperature regime. In this proposed machine, 14.7 MeV proton ripple loss has been calculated using the ORBIT code and it was found the low temperature and high density operation regime is favorable for reducing the ripple losses. For this purpose, the low-temperature and high density operation has been demonstrated in a D-3He fusion using the impurity injection method. Finally the D–D ignition access is demonstrated when 3He fuel is changed to D after reaching the D-3He ignition regime in this proposed ST reactor.

Investigation on a Multimode Switched Reluctance Motor: Design, Optimization, Electromagnetic Analysis, and Experiment

A switched reluctance motor (SRM) with 12/10 poles is investigated in this paper. Compared with the conventional SRMs with single mode, the machine is not only able to be worked as a six-phase motor but also could be used as a three-phase motor, which is thus named multimode SRM (MMSRM). The primary dimensions of the stator and rotor cores are calculated by considering it as a six-phase SRM with long magnetic paths, and the performances of three-phase mode with short magnetic paths are used to test the parameters. The arcs of stator and rotor pole are treated as the optimization objects to minimize torque ripple and copper loss per torque and maximize torque per ampere of the MMSRM. A function is selected to solve the multiobjective problem and the final values of arcs of stator and rotor pole are determined based on the results of finite-element method. The effects of arcs of stator and rotor pole on electromagnetic performances of MMSRM are discussed independently, and a prototype is manufactured to test the simulations. A good agreement between the simulated and measured results verifies the validity of the analytical method and results.

A systematic approach to designing a wide‐current range, MOS capacitor‐based switched‐capacitor DC‐DC converter with an augmenting LDO

SummarySwitched‐capacitor DC‐DC converters (SC DC‐DC) are analyzed for loss sources, voltage regulation integrity, start‐up latency, and ripple size, while the trade‐offs between these metrics are derived. These analyses are used to design a SC DC‐DC that achieves high efficiency in a wide load current range. Four‐way interleaving was employed to reduce the output ripple and efficiency loss due to this ripple. The design can be reconfigured to achieve gains of 1/3 and 2/5 for inputs ranging between 1.4 and 3.6 V to generate output voltage range of 0.4 to 1.27 V and can supply peak load current of 22 mA. It uses thin‐oxide MOS capacitors for their high density and achieves 75.4% peak efficiency with an input frequency of 100 MHz and a load capacitor of 10 nF. An augmenting LDO that only regulates during sudden load transients helps the converter respond fast to these transients. The chip was implemented using a 65‐nm standard CMOS process.

Current Harmonic Compensation for $n$ -Phase Machines With Asymmetrical Winding Arrangement and Different Neutral Configurations

Low-order current harmonics arise in ac drives due to nonlinearities, producing torque ripple and extra losses. In multiphase machines, which offer advantages over three-phase ones, the latter is aggravated because some harmonics map in low-impedance no-torque subspaces. A multiple-resonant-controller (MRC) structure, combining resonant controllers and synchronous frames, was proposed for harmonic cancellation. It permits substantial computational saving over the multiple-synchronous-frame (MSF) strategy, which includes proportional-integral control in one synchronous frame per harmonic. However, such MRC method is only suitable for symmetrical winding arrangements (SWAs), while asymmetrical winding arrangements (AWAs) are also widespread. Adapting the MRC for AWAs is not straightforward, since the harmonic mapping differs significantly from SWAs, and the effect of neutral configurations on it is more complicated and has hardly been studied. In this paper, an MRC strategy for multiphase machines with AWA is developed. Different neutral configurations are considered; particularly, it is shown and taken into account that for a single isolated neutral, unlike with SWAs, certain subspaces are coupled and unbalanced. The optimum frequencies of the resonant controllers and synchronous frames are assessed. The computational burden of the MRC and MSF schemes is compared, and the differences with SWAs are established. Experimental results are provided.

An Asymmetric Three-Level Neutral Point Diode Clamped Converter for Switched Reluctance Motor Drives

An asymmetric three-level neutral point diode clamped converter for switched reluctance motor drives is proposed in this paper. The modulation method, the dc-link voltage balancing algorithm, and the current control scheme of this converter are presented. The proposed three-level converter is compared with the conventional two-level asymmetric half-bridge converter in terms of cost, current ripple, noise, and power losses. Compared to the conventional two-level converter, the proposed three-level converter has much lower current ripple, lower noise, and higher efficiency. The effectiveness of the proposed converter is verified by both simulation and experimental results.

Comparative Study of E-Core and C-Core Modular PM Linear Machines With Different Slot/Pole Combinations

Four modular permanent magnet linear machines (PMLMs) with E-core and C-core primary segments and 12-slot/13-pole (12s/13p) and 12-slot/14-pole (12s/14p) slot/pole combinations are compared in this paper. The influences of flux gap width on the electromagnetic performances and power losses have been investigated based on 2-D finite-element modeling. It has been found that, by choosing proper flux gap width, not only the average thrust force can be improved but also the force ripple and iron losses can be reduced for all the machines. Also, the E-core modular PMLM has higher thrust force and lower detent force compared with the C-core modular PMLM with respect to the same slot/pole combination. Moreover, the 12s/13p modular PMLMs can achieve better electromagnetic performances than the 12s/14p ones regardless of E-core or C-core primary structures. Finally, by shaping the end teeth, the detent force and force ripple of the four modular PMLMs are further mitigated. The 12s/13p E-core modular PMLM is proven to be the best type among these four modular machines.

A 60-kW 3-kW/kg Five-Level T-Type SiC PV Inverter With 99.2% Peak Efficiency

A silicon carbide (SiC) T-type LCL inverter can achieve smaller device loss than two-level topology, however, its improvement on power density is limited by current ripple loss on magnetic components as switching frequency increases. This paper presents a five-level T-type (5LT2) photovoltaic (PV) inverter that achieves better utilization of SiC devices than the traditional three-level T-type LCL topology at higher switching frequency. The operation principle of the SiC 5LT2 PV inverter has been presented. The key design aspects including magnetic balancing, short-circuit protection, and digital controller computation time have been discussed and methods are developed. A 60-kW PV converter including boost stage and inverter stage has been built in the laboratory, which achieves a power density of 27 W/in3 and 3 kW/kg, and measured peak efficiency of 99.2%.

Optimal Design and Implementation of High-Voltage High-Power Silicon Steel Core Medium-Frequency Transformer

A 1.5 kV, 35 kW, 1 kHz silicon steel core medium-frequency transformer is designed and prototyped for a 10 kV, 0.5 MW electronic power transformer. This transformer uses 0.18 mm silicon steel as core material due to the advantages of easy processing, high saturation flux density, low noise, and low cost. The detailed design considerations and an optimal design method are presented in this paper. Different from the previous work on medium-frequency transformer design, the proposed approach takes ripples into account. Core loss model under square wave excitation with ripple and winding loss model considering sideband harmonics are established. Besides, two-dimensional finite-element simulations are adopted to obtain ac/dc resistance factors. Finally, the proposed approach is verified by experiments on prototype. The test results show performance better than expected, with desirable no-load loss and power density of 2.9623 × 106 W/m3.

Calculation of prompt loss and toroidal field ripple loss under neutral beam injection on EAST

Neutral beam injection is a major auxiliary heating method in the EAST experimental campaign. This paper gives detailed calculations of beam loss with different plasma equilibria using the guiding center code ORBIT and NUBEAM/TRANSP. Increasing plasma current can dramatically lower the beam ion prompt loss and ripple loss. Countercurrent beam injection gives a much larger prompt loss fraction than co-injection, and ripple-induced collisionless stochastic diffusion is the dominant loss channel.

Design of permanent magnet synchronous generators for wave power generation

In this paper, a design method for ocean wave permanent magnet synchronous generator(PMSG)is proposed with new performance criteria to obtain better output performance at the cost of less permanent magnet material. Besides, a simple equivalent analytical geometry method is put forward to calculate the sizes of permanent magnets. Based on geometric and electromagnetic models, four types of rotor structures are compared, i.e., embedded, tangential, tile surface mount and convex surface mount structures. The designs and comparisons of machine are performed with the same permanent magnet volume. Moreover, the influences of mechanical pole-arc coefficient of tile surface mount PMSG on electrical efficiency, output power, material corrosion, core loss, and torque ripple are investigated. Finite-element analysis method is applied to verify the results using Ansoft/Maxwell.