Transient Overload Research Articles

Stabilization of liquid tin surfaces under D plasma irradiation by a capillary porous system

Liquid metal divertors are discussed as a potential alternative to divertor components made entirely of solid materials such as tungsten. However, liquid metal interaction with H isotope plasmas poses entirely new challenges, including the stability of the liquid surface. In this article, the interaction of low-temperature D plasmas with both free liquid tin surfaces, and the liquid metal confined in a capillary porous system (CPS) is presented. Free surfaces showed intolerable instabilities due to formation of gas bubbles in the melt, as opposed to a strong stabilizing effect of the CPS. A tendency of liquid tin to well up and entirely cover the surface of the CPS may be beneficial in terms of quickly re-establishing a tin surface after depletion by transient overloading. On the other hand, this appears to counteract efforts to fully suppress superficial bubble formation and bursting, and the resulting ejection of tin droplets by designing a CPS with very small pores.

Open-Phase-Tolerant Online Current References for Maximum Torque Range and Minimum Loss With Current and Torque-Ripple Limits for n-Phase Nonsalient PMSMs With Nonsinusoidal Back EMF

Multiphase permanent-magnet synchronous machines (PMSMs) with nonsinusoidal back-electromotive force (back-EMF) offer high fault tolerance and torque density for electric vehicles. Most current-reference generation methods either minimize stator copper loss (SCL) or maximize achievable torque. Optimization of both goals is accomplished by full-torque-range minimum-loss (FRML) strategies, but so far just for sinusoidal back-EMF. Thus, FRML for nonsinusoidal back-EMF should be sought. Moreover, many methods are only suitable for healthy conditions or specific machines, harmonics, or open-phase-fault (OPF) scenarios. Additionally, the torque range may be extended by permitting torque ripple or (transiently) greater rms current, but this approach is not general nor FRML yet. This paper proposes online FRML current-reference generation for multiphase PMSMs with nonsinusoidal back-EMF: nonsinusoidal-back-EMF FRML (NSBE-FRML). When the torque reference is feasible, minimum SCL is attained while maximizing the achievable torque (i.e., FRML). For higher torque references, the instantaneous torque deviation is minimized, and the torque reference is saturated in consecutive samples limiting the torque ripple to a pre-specified threshold. Furthermore, the rms current is limited after transient overload by automatically decreasing the torque reference. The NSBE-FRML is suitable for any harmonics, healthy/OPF conditions, and multiphase PMSMs with negligible saliency ratio. Experiments are performed with a six-phase PMSM.

Grid connection transients of small hydropower generator

This paper presents a transients of an cage induction generator connected to the power grid as it is in small hydropower station. In such power station, there is no control of prime mover speed. The no load speed of water turbine and then induction generator depends on reservoir water level and water pipe diameter. The transient state during connection of the cage induction generator to the power grid is discussed in dependence on generator initial slip. The negative impact of connected cage induction generator on the line is described. The transient current to grid connected generator is very high and produces transient overload of the supply system. The reduction of that negative influence is proposed by using a power electronics converter which works as reactive power compensator. The power electronic compensator is used in steady state to reduce demand of the grid reactive power needed by induction generator and in transients to reduce surge current. The computer model of the generation system, made form induction generator and power electronic compensator, has been designed and used to preliminary verification. Moreover a laboratory generation system has been built and tested.

Mixed Convective Heat Transfer Characteristics of Graphene Nanofluid Strengthened by Periodically Direction-Switching Electric Field

Abstract Transformer-oil with low thermal conductivity and large viscosity has poor heat dissipation capability, which leads to the thermal drive failure caused by transient overload. To improve its cooling capability, this paper has proposed first the method which combined the periodically direction-switching electric field and graphene nanofluid to enhance the mixed convective heat transfer properties of transformer-oil, and analyzed the effects of switching periods, nanofluid concentration, electric field strength, heat flux, and Reynolds number on mixed convection heat transfer experimentally. The results show that the heat transfer characteristic of transformer-oil is improved up to 52% by the periodically direction-switching electric field and graphene nanofluid. As the switching period decreases, the thermal performance of the suspension is enhanced more significantly. Moreover, by analyzing the heat transfer mechanism, the periodically direction-switching electric field causes the nanoparticles to move reciprocally, repeatedly impacting and breaking the boundary layer of the heat exchange surface to enhance the perturbation, thus enhancing the heat transfer effect. Meanwhile, the predicted correlation has been proposed on the basis of influence factors, which are in good agreement with the experimental data.

General Online Current-Harmonic Generation for Increased Torque Capability With Minimum Stator Copper Loss in Fault-Tolerant Multiphase Induction Motor Drives

This paper proposes a current-reference generation method including current harmonic injection (CHI) for enhancing the torque capability of multiphase induction machines (IMs) with negligible space-harmonic effects, which is useful, e.g., during transient overload in electric vehicles. The admissible torque is increased because the harmonics reduce the phase-current peaks, so that the instantaneous peak-current constraint of the drive, usually associated with the converter ratings, is respected. The harmonics are injected in the so-called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x-y</i> subspaces of the IM, which do not produce torque, so that no torque ripple is introduced. The optimum harmonics are found online for each load, making it possible to minimize the stator copper loss (SCL) per torque in the entire torque range, ensuring full-range minimum loss (FRML). The method is suitable for healthy operation or open-phase faults, and for multiphase machines of any phase number and with either symmetrical or asymmetrical windings. Compared with FRML methods without CHI, higher torque is achieved. Although some techniques were available for increasing the torque capability by CHI, FRML was not attained, laborious offline optimization was needed, or they were only suitable for specific drives or for healthy conditions, unlike the proposal. Experimental results with a symmetrical six-phase IM are provided.

Decentralized Robust Control of a Network of Inverter-Based Distributed Generation Systems

This paper presents the design of decentralized robust controllers for a network of inverter-based distributed generation systems with LC filters in the scale of a nanogrid. Using overlapping decomposition, the network of inverters is clustered into several subnetworks such that all inverters within a subnetwork are strongly coupled and there is no or a weak coupling effect between any two inverters from different subnetworks. For the inverters within the same subnetwork, decentralized robust controllers are designed sequentially in the μ-synthesis framework. In addition, all controllers are designed to be robust against ±10% variations in the LC filter parameters. To assess the performance of the proposed sequentially-designed controllers and compare it to that of the benchmark independently-designed ones, the distances between two neighboring inverters from the same and different subnetworks are considered to be 200 (m) and 800 (m), respectively. In this case, time-response and robustness analysis results illustrate the superiority of the proposed sequentially-designed controllers in the overlapping decomposition framework over the benchmark independently-designed ones. Moreover, transient overload and nonlinear load analyses demonstrate that the proposed sequentially-designed decentralized controllers are able to keep the load voltage within ±10% of the nominal value and the harmonic voltage distortions to less than 4%.

710 NEW PROSPECTIVES IN THE USE OF ELECTROCARDIOGRAM IN ANDERSON-FABRY DISEASE ON AND OFF SPECIFIC DISEASE THERAPY: EARLY DIAGNOSIS AND RESPONSE TO THERAPY

Abstract Background Anderson Fabry disease (AFD) is a rare X-linked lysosomal storage disorder caused by deficient activity of α-galactosidase A bringing to intracellular accumulation of globotriaosylceramide (Gb3) in affected tissues, including heart. Progressive cardiac involvement has shown to cause electrocardiographic modifications in these patients. Treatment with enzyme replacement therapy (ERT) or chaperone therapy has demonstrated to decrease Gb3 levels in the heart, but little is known about its influence on ECG evolution. Purpose to gain new insights about ECG evolution in AFD patients on and off specific disease therapy and to assess its potential role in the diagnosis and the follow-up of these patients. Methods we analysed the ECG evolution of a multicentre study cohort of 170 patients with a diagnosis of AFD (64 males 38%, median age 46±15 years) for a median follow-up of 64±48 months, dividing them into patients off (group A, N=63) and on (group B, N= 107) specific therapy. Results the two groups did not differ as regard age at baseline (47±14 vs 44±12 years; p=0,171) but patients off specific disease therapy (group A) showed lower prevalence of male sex [13(21%) vs 51(48%); p=&amp;lt;0,001], classic phenotype [36(57%) vs 82(77%); p&amp;lt;0,001)] and lower values of maximal wall thickness [11±3 vs 13±4 mm; p=&amp;lt;0,0001]. At baseline group A presented more frequently a normal ECG [44(70%) vs 41(38%), p=0,0001] showing lower prevalence of repolarization anomalies [16(25%) vs 51(48%), p=0,005] and left ventricular hypertrophy [14(22%) vs 51(48%), p=0,001]. During follow-up we observed ECG progression in 9 patients in group A (14%), characterized by the development of repolarization anomalies (N=5; 8%), incomplete right bundle branch block (N=4; 6%), shortening of PR interval (N=2; 3%), left ventricular hypertrophy (N=2; 3%), left atrial enlargement (N=2; 3%) and complete right bundle branch block (N=1; 2%). Differently, in group B an ECG evolution was observed in 31 patients (29%) characterized by the development of repolarization anomalies (N=19; 18%), left atrial enlargement (N=12; 12%), complete right bundle branch block (N=8; 8%), left anterior fascicular hemiblock (N=4; 4%) and left ventricular hypertrophy (N=3; 3%).We observed an improvement in ECG features with a regression of repolarization anomalies only in 1 patient off therapy, which could be explained by the presence of transient overload anomalies. We didn't detect any left bundle brunch block among the patients of the two groups. Conclusion We observed ECG progression despite specific disease therapy in 29% of patients of group B showing a potential role of ECG as a marker of cardiac specific response to therapy in these patients. Differently we detected ECG progression in 14% of patients off specific therapy, which is consistent with their less advanced cardiac involvement (lower prevalence of male sex, classic phenotype and lower maximum wall thickness), suggesting that ECG could be an important tool to detect an initial cardiac involvement in these patients even in absence of hypertrophy. The absence of left bundle branch blocks in the two groups compared with a significant prevalence of complete and incomplete right conduction delay could suggest a prevalent involvement of the right bundle branch in these patients and could represent a red flag for the diagnosis of AFD.

Provably-Stable Overload Ride-Through Control for Grid-Forming Inverters Using System-Wide Lyapunov Function Analysis

A key challenge associated with a grid-forming (GFM) inverter based resource (IBR) is its behavior during severe grid disturbances: since a GFM inverter regulates voltage in the fast timescale instead of current or power, it may experience a transient overload of current, power and/or energy during a severe grid disturbance. While many promising control strategies for overload ride-through have been proposed over the past two decades, transient stability of the system during and after the transition to an overload ride-through control mode remains difficult to guarantee. In this article, a novel overload ride-through control strategy is proposed for a system of grid-forming inverters that takes both self-protection and system-wide transient stability into account. A proposed system-level supervisory control uses slow communication to pre-emptively assign a set of local ride-through control parameters to individual GFM IBR, including a current-limiting virtual reactance, that guarantees that synchronism is still preserved for any set of anticipated grid disturbances. At the core of the supervisory control lies a Lyapunov-function-based routine capable of establishing a strong, albeit conservative, transient stability guarantee for the system. The proposed overload ride-through control strategy is validated via numerical integration of a reduced-order model, as well as through detailed electromagnetic transient (EMT) simulation.

Coupled Electromagnetic–LPTN Analysis Under Steady and Transient Overload Condition of High-Speed PMSM for Mechanical Vapor Recompression Applications

Coupled Electromagnetic–LPTN Analysis Under Steady and Transient Overload Condition of High-Speed PMSM for Mechanical Vapor Recompression Applications

Electrocardiographic evolution in Anderson-Fabry disease patients on and off specific therapy: a potential marker to study the therapeutic cardiac goal

Abstract Background Anderson Fabry disease (AFD) is an X-linked lysosomal storage disorder leading to a deficiency in α-galactosidase A and globotriasylceramide (Gb3) deposition in different organs, including the heart. In AFD patients electrocardiogram (ECG) represents an important tool to detect cardiac involvement. AFD specific therapy (enzyme replacement or chaperon therapy) has shown to modify the natural history of the disease and to decrease Gb3 levels, but so far there are no data on its influence on ECG evolution. Purpose To assess the progression of ECG features in AFD patients on and off specific disease therapy and to evaluate the potential role of ECG in studying the cardiac specific response to therapy. Methods We recruited 170 patients with an established AFD diagnosis, ≥18 years old (64 males 38%, median age 46±15 years) in a multicentre study cohort. We analysed their ECG evolution for a median follow-up of 64±48 months in patients off (group A, N=63) and on (group B, N=107) specific therapy. Results AFD patients off specific disease therapy (group A) had similar age at baseline compared to those on therapy (47±14 vs 44±12 years; p=0,171), however significantly differed for males prevalence [13 (21%) vs 51 (48%); p≤0,001], classic phenotype [36 (57%) vs 82 (77%); p&amp;lt;0,001)] and maximal wall thickness [11±3 vs 13±4 mm; p≤0,0001]. As regards ECG features at baseline, group A showed a lower prevalence of repolarization anomalies [16 (25%) vs 51 (48%), p=0,005], left ventricular hypertrophy [14 (22%) vs 51 (48%), p=0,001], pseudo necrosis [4 (6%) vs 18 (17%) vs, p≤0,060] and short PR [2 (3%) vs 12 (11%), p=0.0845]. During the follow-up ECG progression was observed in 9 patients in group A (14%), characterized by the development of repolarization anomalies (N=5; 8%), incomplete right bundle block (N=4; 6%), shortening of PR interval (N=2; 3%), left ventricular hypertrophy (N=2; 3%), left atrial enlargement (N=2; 3%) and complete right bundle block (N=1; 2%). Differently, in group B an ECG evolution was observed in 31 patients (29%) characterized by the development of repolarization anomalies (N=19; 18%), left atrial enlargement (N=12; 12%), complete right bundle block (N=8; 8%), left anterior fascicular hemiblock (N=4; 4%), left bundle block (N=4, 4%) and left ventricular hypertrophy (N=3; 3%). Among patients off therapy we observed an improvement of ECG in 1 patient characterized by regression of repolarization anomalies, which could be explained with the presence of transient overload anomalies. Conclusion In AFD patients off and on specific disease therapy, ECG evolution was detected in 14% and 29% respectively, consistently with the more advanced cardiac involvement in patients on therapy (higher prevalence of male sex, classic phenotype and higher maximum wall thickness). The fact that one third of the patients showed ECG changes progression despite being on specific disease therapy could be relevant to better defined the therapeutic cardiac goal. Funding Acknowledgement Type of funding sources: None.

High-heat-flux performance limit of tungsten monoblock targets: Impact on the armor materials and implications for power exhaust capacity

• Results of the extensive high-heat-flux tests of tungsten monoblock-type divertor target mock-ups are presented. • Impacts of various slow/short transient overloads relevant to European DEMO divertor on the armor materials and the joining interfaces are addressed. • Comprehensive high-quality data comprising in-situ IR thermography, ultrasonic reflectometry and electron microscopy (EBSD) are presented. • Implications of the novel test results for the power exhaust requirements are discussed. Development of a reliable high-heat-flux (HHF) technology is one of the crucial requirements of power exhaust strategy for a fusion reactor. The baseline HHF technology of the EU-DEMO, which inherited mostly the ITER technology, is based on the tungsten monoblock design and hot radial pressing joining technique. Thermal resilience and structural integrity under all off-normal transient events foreseen are essential prerequisites for validation of the technology towards the demonstration of full-scale prototype manufacture. Hence, the HHF performance of the baseline technology needs to be evaluated also in the transient overload regime. To this end, we conducted an extensive HHF testing campaign using small-scale test mock-ups of the tungsten monoblock target for two slow (10s) overloads at 20 MW/m 2 (up to 2000 pulses) and 25 MW/m 2 (1000 pulses), and for a short (0.4s) overload at 40 MW/m 2 (5000 pulses). Furthermore, excessive heat loads (32-37 MW/m 2 ) were applied beyond the armor melting event to test the structural stability at limit loads. IR thermography, ultrasonic inspection and electron microscopy (EBSD) delivered direct information and insight on the structural integrity and the impact on the armor microstructure. It was found that the tungsten monoblock target remained fully intact at least up to 1000 heating cycles at 20 MW/m 2 (10s) and survived 2000 cycles without any major failure. At 25 MW/m 2 (10s), the mock-ups remained nearly intact at least up to 500 heating cycles and survived 1000 cycles without critical failure. However, the armor surface showed substantial deformation roughening with the height of 1000 µm after 1000 cycles. At 40 MW/m 2 with short pulses (0.4s), the mock-ups remained fully intact without any serious damage at least up to 5000 cycles. The mock-ups even withstood the limit heat load of 32 MW/m 2 at least for a few pulses. Under excessive overloads (33-37 MW/m 2 ) above the critical incident heat flux, armor melting preceded any other potential failures (e.g. pipe rupture by coolant boiling).

Integrating I-DEVS and schedulability methods for analyzing real-time systems constraints

The design of embedded real-time systems (RTS) is challenging due to the criticality of the timing constraints of these systems. Various informal and formal methods for RTS design have been proposed, both in the design space and the real-time execution at the hardware level, but many of these methods are not effective when the complexity of the system scales up. Here, we discuss a new method to integrate a modeling (and simulation) formalism that allows designing complex systems specifications for real-time constraints called Imprecise-DEVS (I-DEVS), and the mapping of such high-level models into a real-time task model. This method allows analyzing real-time constraints both at the high level of modeling as well as the low level of the tasks executed by the processing units and the Operating System. A new method to study the schedulability of the task models is proposed. The method provides a design analysis space from the model level, up to the individual tasks, with a focus on the schedulability of real-time constraints under transient overloading conditions.

Coordinative frequency-constrained unit commitment model for HVDC interconnected AC systems

Considering the increasing penetration of renewable energy resources (RES) and the higher capacity of HVDC system that responsible for RES transition, our paper proposes a coordinative frequency-constrained unit commitment (FCUC) model to manage the frequency stability after credible contingency with bulk power loss. The robust enhanced emergency frequency control strategy is proposed in this paper, wherein the transient overload capabilities of HVDC system are exploited to provide inertial response when ensuring the effectiveness and speed. Afterwards, the AC-DC primary response model considering the descent rates of HVDC is derived for the first time. This HVDC decline induces an extra steady-state power rescheduling procedure in this model, based on day-ahead schedule and emergency control procedures, the optimized AC-DC secondary response solution in power rescheduling further promotes the model economic benefits. In view of the max–min structure of emergency control problem and the solution domain formation of power reschedule problem, an improved three-level algorithm combining the features of Benders decomposition and C&CG method is developed to solve the problem. After applying the proposed coordinative FCUC model on two scales of asynchronous systems with parallel HVDC lines interconnection, it is validated that by formulating the multi-speed response services among procedures coordinately, the flexibility of operation scheme is further excavated.

ESD Stress Analysis and Suppression in a Single-Junction Thermal Converter

This article presents an outline of Electric Transient Disturbances (ETDs), represented by the ElectroStatic Discharge (ESD) in accordance with the Human-Body Model (HBM), on the AC-DC transfer measurement standard, represented by the Single-Junction Thermal Converter (SJTC) Thermal Element (TE). Mitigation technique against the power dissipation build-up, higher than the operational margins recommended by a manufacturer, on the TE were proposed and modelled using Laplace Transform (LT) analysis. A mathematical model and an optimization algorithm were developed to determine the equivalent circuit model parameters of a Transient Overload Protection Module (TOPM) that would offer adequate protection against destructive power dissipation levels build-up on the TE. The mathematical model was developed using an 8 kV ESD, which was expected to deliver short-circuit current with a peak value of approximately 5.33 A through a load impedance of approximately 1 m\varOmega. The ESD stress signal was injected into the TOPM connected in parallel with the TE. The active power dissipated by the SJTC TE per period of transient response was calculated from the current and voltage obtained from the mathematical analysis, and the results indicate a power dissipation of 10 mW by the TE. From the algorithm, the model parameter that noticeably influences the power dissipation capabilities of the TOPM is the inductance and it must be smaller than 1.2 nH. A CAD based simulation model was developed and analysed. The simulation results agreed with the mathematical model.

PLL-Free Voltage Oriented Control Strategy for Voltage Source Converters Tied to Unbalanced Utility Grids

Asymmetrical working conditions of the utility grid introduce the large-amplitude negative-sequence component to the output current of the voltage source converter (VSC), causing power semiconductor devices to suffer from thermal fatigue and thermal damage. Though the conventional phase-locked loop (PLL) based voltage oriented control (VOC) solution can suppress the steady-state negative-sequence current effectively, it has a weak suppression ability of transient overload current, and even aggravates the transient current asymmetry and causes more severe transient impact to the VSC. This paper first analyzes the transient performance of the conventional VOC strategy, especially its dynamic response time and the main factors for performance limitation. On this basis, the PLL-free VOC strategy for VSCs tied to unbalanced grids is proposed, and its critical parts, namely, the reference current calculation and the fast detection of the grid voltage sequence components, are implemented. Besides, to improve the frequency adaptability, a high-performance grid frequency detection strategy is developed based on the difference-frequency phase caused by the frequency variation. Finally, experiments are performed to verify the effectiveness and advancement of the proposed method. Specifically, the results proved the rapidity, accuracy, and frequency adaptability of the proposed method in suppressing the VSC negative-sequence current, both in transient and steady-state conditions.

Effect of Endogenous Failure Events on the Survivability of Turboelectric Distributed Propulsion System

Recent advancements in aircraft electrification have led to the introduction of turboelectric distributed propulsion (TeDP). For instance, NASA&#x0027;s N3X airplane aims to curb jet fuel emissions with the aid of TeDP. However, it is crucial to analyze the survivability of the TeDP system during extreme conditions. The endogenous failure events are of specific interest as they were found to cause a significant number of accidents for commercial aircraft. While the distribution reconfiguration is necessary to meet the critical load demands under extreme failure events, it can also create a transient overload condition in the turboshaft engine. The power system survivability is further deteriorated in the presence of constant power loads. In this article, a mathematical analysis of the survivability of the system is presented to make the aircraft power system highly resilient to endogenous failure events. A power system collapse mitigation strategy is proposed by adding an energy storage system. Moreover, the analytical expressions are formulated to size the energy storage unit to prevent the system collapse. Various failure conditions are modeled using PSCAD&#x002F;EMTDC to study the minimum energy storage required to prevent system collapse.

Numerical and experimental studies on the thermal and static characteristics of multi-leaf foil thrust bearing

Foil bearing is considered to be a promising supporting technology in high-speed centrifugal machinery. Due to the high-speed shearing effect in the viscous lubricant film, heat generation could not be ignored. In this paper, a thermo-elastic model of the multi-leaf foil thrust bearing is proposed to predict its thermal and static characteristics. In the model, modified Reynolds equation, energy equation, and Kirchhoff equation are solved in a coupling way. The contact area between the foil and welding plate is taken into account. Besides, the effect of cooling air on the bearing temperature is investigated. The ultimate load capacity and transient overload failure process of the bearing is analyzed and discussed. The effect of rotation speed on the bearing temperature is more obvious than that of the bearing load. The bearing temperature drops obviously by introducing the cooling air, and the cooling effect is improved with the supply pressure. The transient overload failure of the bearing occurs when the bearing load exceeds the ultimate value.

A deferring strategy to improve schedulability for the imprecise convergence on-line tasks

The imprecise real-time scheduling can be used for minimizing the bad effects of timing faults by leaving less important tasks unfinished if necessary when a transient overload occured. In the imprecise scheduling, every time-critical task can be logically decomposed into two tasks : a mandatory task and an optional task. Recently, some studies in this field showed good schedulability performance and minimum total error by deferring the optional tasks. But the schedulability performance of the studies can be shown only when the execution time of each optional task was less than or equal to the execution time of its corresponding mandatory task. Therefore, in this paper, a new deferring strategy is proposed under the reverse execution time restriction to the previous studies. Nevertheless, the strategy produces comparable or superior schedulability performance to the previous studies and can minimize the total error also.

Hybrid-Excited PM Motor for Electric Vehicle

This paper deals with the potentials of a Hybrid-Excitation Permanent-Magnet (HEPM) machine. The HEPM machine is characterized by a rotor including both permanent magnets (PMs) and excitation coils. The PMs produce a constant flux at the air gap of the machine, while an excitation current is supplied so as to regulate such a flux. A flux increase could be necessary during transient overload operations, while a flux decrease is useful during Flux-Weakening (FW) actions to operate at speeds higher than the nominal speed. Torque, power, efficiency, flux density and losses of an interior permanent magnet (IPM) motor and an HEPM motor are analyzed in detail. It is shown that this excitation winding produces a great advantage in terms of torque and power performance during the operations at speeds higher than the nominal speed. Despite the additional rotor losses, it is shown that there is a higher efficiency.

Thermal capability of electric vehicle PMSM with different slot areas via thermal network analysis

In this paper, the effect that a varied stator slot size has on the efficiency and thermal capability of a permanent magnet synchronous machine for an electric vehicle, is evaluated and quantified. A machine with four differently sized slot areas was electromagnetically evaluated with finite element analysis, and thermally with a lumped parameter network model. By decreasing the slot size while keeping other dimensions fixed, the core losses reduce due to the wider magnetic path, whereas the winding losses increase. Additionally, a higher maximum torque is reached due to reduced saturation. Results are compared in the machine’s torque-speed operating area regarding machine-part and total losses, continuous torque and transient overload capability, as well as during 19 low, middle and high-speed drive cycles regarding energy losses and peak winding temperature. The largest slot showed the lowest winding losses and thus the highest thermally limited torque capability. In contrast, the energy losses with the largest slot were the highest in 13 of the drive cycles, and the lowest in 11 of them with the smallest slot due to its lower part load (i.e. core) losses. The smallest slot would also result in the lowest material cost since it has the least copper. • Larger PMSM stator slot gives higher continuous torque than a smaller with same rotor and current. • Smaller PMSM stator slot gives higher peak torque than a larger with same rotor and peak current. • Smaller PMSM stator slot gives lower total losses than a larger during many official drive cycles.