1,721,260 research outputs found
Psychosocial interventions and opioid detoxification for drug misuse: summary of NICE guidance
No full textDrug misuse is an increasing problem that not only impairs the physical and mental health of people who misuse drugs but also negatively affects their families and wider society (for example, in its association with crime). Recently expanded drug services in the United Kingdom involve general practitioners to a considerable degree, who care for at least a third of opioid misusers in treatment. Many clinicians remain pessimistic, however, about the possible benefits of any treatment and how to engage drug users in treatment.1 This article summarises two new NICE guidelines that identify the most effective, safe detoxification regimens for primary and secondary care, the most cost effective psychosocial interventions, and effective ways to promote patient engagement
Sensitivity analysis of magnetizing inductance in solid rotor induction machine
No full textSolid Rotor Induction Machines (SRIM) gained lot of interesting in the last decades due to the increasing demand for high speed drives. The low manufacturing cost, the rotor robustness and the capability operating in of harsh environments comes along with the drawbacks of difficult design process, necessity of multi-physics analysis and poor power factor. The magnetizing inductance play an important role for what concerns the power factor. In this work the impact of the solid rotor material properties and the air gap of the machine on the magnetizing inductance is investigated
Thermal-Electromagnetic Analysis of Solid Rotor Induction Machine
No full textThe increasing demand for high speed, direct drive systems is driving a significant research effort on high speed electrical machines. Thermal management becomes a significant aspect to deal with as power loss per cooling surface area reduces as speed increases. Solid rotor induction machines are often considered at the high end of the speed spectrum as they offer a mechanically robust rotor structure. The current density distribution within their rotor structure typically results in high rotor losses and a significant portion of the total machine losses. In such machines the current distribution in the rotor itself is highly dependent on the rotor resistance and hence on the rotor temperature distribution. This paper will detail an effective model coupling both the electromagnetic and thermal domains to simulate operation of solid rotor induction machines
Sensitivity analysis of rotor parameters in solid rotor induction machine
No full textSolid Rotor Induction Machines (SRIM) gained lot of interesting in the last decades due to the increasing demand for high speed drives. The low manufacturing cost, the rotor robustness and the capability operating in of harsh environments comes along with the drawbacks of difficult design process, necessity of multi-physics analysis and poor power factor. The single phase lumped parameter equivalent circuit is widely adopted for design and analysis purposes. The impact of the solid rotor material properties as saturation flux density, relative permeability and electrical resistivity are discussed in this work for what concerns mainly the rotor resistance and rotor leakage inductance. Finite Element simulations are performed to determine the equivalent circuit parameters dependencies on the solid material selected for the rotor structure
Development and testing aspects of high speed induction machines
No full textThis paper reviews the development and testing aspects of high speed induction machines, through a case study involving a 120 [kW], 25000 [rpm] Induction Machine for a power generation application. In the first part, developments in materials and components including electrical steels and copper alloys are discussed, and their impact on the machines' design and construction is investigated. In the second part of this paper, the testing aspects and test results of the prototyped Induction Machines are reported
A high-speed permanent-magnet machine for fault-tolerant drivetrains
Full text linkThis paper details the design considerations of a permanent magnet (PM), three phase, high speed, synchronous machine for fault tolerant operation. A multidisciplinary approach to the optimal design of the machine is adopted targeted at minimising the additional losses resulting from faulty operating conditions and accounting for the remedial control strategy implemented. The design of a closed slot, 6 slots, 4 pole machine is presented. The machine is prototyped and tested to validate the analytical-computational performances predicted in the design and analysis stage under healthy and faulty condition
Demagnetisation analysis for Halbach array configurations in electrical machines
Full text linkThis paper proposes and investigates an analytical method for assessing the risk of potential, irreversible demagnetisation in the PMs of electrical machines, equipped with n-stages, Halbach arrays. The higher risk of demagnetisation, synonymous with Halbach arrays imposes that the method be both load and temperature dependant. In fact, the proposed method studies the magnetic field distribution in the air-gap and PM region, for various operating temperatures and expresses these fields as analytical expressions for the no-load and peak load conditions. The model can cater for Halbach arrays with up to n stages, thus making it a versatile tool that can be utilised for various Halbach configurations. Finite element analysis is used to validate the method.
The analytical tool is then used for the design and analysis of a high torque density, outer rotor, traction motor. The motor is for an aerospace application and its operating duty cycle imposes very high, short time, peak load conditions at elevated temperatures, posing an elevated risk of irreversible, PM demagnetisation. The model is used to investigate various Halbach configurations for this application, in order to reduce the demagnetisation risk and also improve the general performance of the machine. The analytical method thus provides a computationally efficient tool that can be used to predict and prevent demagnetisation in Halbach-equipped, electrical machines operating in harsh environments such as the aerospace sector
Braking torque compensation strategy and thermal behavior of a dual three-phase winding PMSM during short-circuit fault
No full textPermanent magnet synchronous machines (PMSMs)employing the dual three-phase winding represent a suitable solution for complying with the reliability requirements typically needed in safety-critical applications. Their inherent fault-tolerant capability allows to operate the system (e.g. electro mechanical actuator or traction drive-train), even after the occurrence of a three-phase short-circuit in one winding set. Nevertheless, an appropriate post-fault control strategy is indispensable for preventing the PMSM performance derating. In this work, the design of a dual three-phase PMSM, intended for aerospace application, is presented. The PMSM performance is evaluated via finite element (FE)analysis, in both healthy and three-phase short-circuit conditions. A post-fault control strategy aimed at balancing the braking torque is then discussed. Since the implemented strategy is based on the current overload of the healthy winding, the temperature rise is experimentally investigated on the PMSM prototype. The thermal analysis verifies the compensation strategy feasibility, by proving that the thermal overload does not have a major effect on the wire insulation lifetime
Permanent magnet reduction by current harmonics injection for surface permanent magnet machines
No full textThis paper presents the analysis of multi-harmonic current injection in multi-three phase surface permanent magnet (SPM) machines. An analytical model, extended to a generic harmonic order, is used to describe and determine the no load flux density, the back electromotive force (BEMF) and the electromagnetic torque produced. These are analysed as a function of the permanent magnet span. Based on the BEMF, the harmonics injection technique is adopted to increase the torque in the machine, while keeping the RMS current constant, thus without affecting the Joule losses. In order to understand how the torque is affected by the harmonics injection, considering different PMs rotor span, a comparison with and without injection is presented. It is shown how, thanks to specific harmonics injection, it is possible to reduce the permanent magnet content in SPM machines while generating the same torque performance of a motor with higher PM content, without harmonic injection. The analytical results are finally validated by means of Finite Element Analysis (FEA) considering two different PM rotor span, as a case study, highlighting the benefits of the proposed method
Structural design optimization of a high speed synchronous reluctance machine
No full textSynchronous reluctance machines, including the permanent magnet assisted variants are competitive motor topologies if the application requires high efficiency and a cost effective solution with a high flux weakening capability. However, increasing speeds incur challenging design and development decisions, in order to find an optimal solution between the machine performance and its structural integrity. In this paper, a comprehensive design procedure for such machines is presented, where a 5kW, 80000 rpm synchronous reluctance machine is considered. The proposed strategy consists of a two-step procedure in which the electromagnetic and structural designs have been properly decoupled dividing the design space in two subsets. Each subset mainly affects the electromagnetic or the structural performances. Several structural design optimizations have been performed with the aim of finding the optimal trade-off between the rotor geometrical complexity (i.e. computational time) and the electromagnetic performance. The results shown in this paper validate the proposed design strategy which can be used as general guidelines on the structural design of synchronous reluctance machines
- …
