scholarly journals Thermally Induced Mechanical Stress in the Stator Windings of Electrical Machines

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2113 ◽  
Author(s):  
Bishal Silwal ◽  
Peter Sergeant
Keyword(s):  
Mechanical Stress ◽  
Temperature Cycling ◽  
Electrical Machines ◽  
Electrical Machine ◽  
Thermally Induced ◽  
Stator Windings ◽  
Mechanical Models ◽  
Set Up ◽  
Winding Insulation ◽  
Main Factor

The lifetime of an electrical machine mainly depends on the thermal overloading. Modern day applications of electrical machines on one hand require compact machines with high power density, while on the other hand force electrical machines to undergo frequent temperature cycling. Until recently, in the case of electrical machines, the main factor related to the degradation of the winding insulation was thought to be the thermal oxidization of the insulation materials. It has now been revealed that thermal overloading can also induce mechanical stress in the windings of electrical machines, which over time could lead to fatigue and degradation. In this paper, a comprehensive study of the thermally induced mechanical stress in the windings of an electrical machine is presented. The study is performed using combined thermo-mechanical models. The numerical results are validated by experiments on a segmented stator winding set-up.

scholarly journals Assessment of Different Cooling Techniques for Reduced Mechanical Stress in the Windings of Electrical Machines

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1967 ◽  
Author(s):  
Bishal Silwal ◽  
Abdalla Hussein Mohamed ◽  
Jasper Nonneman ◽  
Michel De Paepe ◽  
Peter Sergeant
Keyword(s):  
Mechanical Stress ◽  
Thermal Loading ◽  
Three Dimensional ◽  
Electrical Machines ◽  
Water Jacket ◽  
Traction Motors ◽  
Dimensional Finite Element ◽  
Mechanical Models ◽  
Set Up ◽  
Three Dimensional Finite Element

Thermal loading can induce mechanical stresses in the windings of electrical machines, especially those impregnated with epoxy resins, which is mostly the case in modern traction motors. Although designers look for cooling techniques that give better performance in terms of the power density and efficiency of the machine, several thermal cycles can lead to fatigue and the degradation of the copper insulation, epoxy and consequently the windings. In this paper, the performance of different cooling techniques has been compared based on the temperature distribution and the mechanical stress induced in the windings. Three-dimensional finite element thermo-mechanical models were built to perform the study. Two different variants of water jacket cooling, two configurations of direct coil cooling and two cases of combined water jacket and direct coil cooling methods have been considered in the paper. The results show that the combined water jacket and direct coil cooling perform the best in terms of the temperature and also the mechanical stress induced in the windings. An experimental set-up is built and tested to validate the numerical results.

scholarly journals Mechanically and Thermally Induced Degradation and Modification of Cereal Biopolymers during Grinding

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 448 ◽  
Author(s):  
Sabina Paulik ◽  
Mario Jekle ◽  
Thomas Becker
Keyword(s):  
Mechanical Stress ◽  
Structural Modification ◽  
Wheat Starch ◽  
Water Addition ◽  
Scanning Calorimetry ◽  
Hydration Properties ◽  
Thermally Induced ◽  
Induced Changes ◽  
The Impact ◽  
Main Factor

It is presumed that structural and functional alterations of biopolymers, which occur during grinding, are caused by a mechanical modification of polymers. As a result, thermally induced changes of flours are neglected. In this study, the impact of thermo-mechanical stress (TMS), as occurring during general grinding procedures, was further differentiated into thermal stress (TS) and mechanical stress (MS). For TS, native wheat flour, as well as the purified polymers of wheat—starch and gluten—were heated without water addition up to 110 ∘ C. Isolated MS was applied in a temperature-controlled ultra-centrifugal grinder (UCG), whereby thermal and mechanical treatment (TMS) was simultaneously performed in a non-cooled UCG. TS starch (110 ∘ C) and reference starch did not show differences in starch modification degree (2.53 ± 0.24 g/100 g and 2.73 ± 0.15 g/100 g, AACC 76-31), gelatinization onset (52.44 ± 0.14 ∘ C and 52.73 ± 0.27 ∘ C, differential scanning calorimetry (DSC)) and hydration properties (68.9 ± 0.8% dm and 75.8 ± 3.0%, AACC 56-11), respectively. However, TS led to an elevated gelatinization onset and a rise of water absorption of flours (Z-kneader) affecting the processing of cereal-based dough. No differences were visible between MS and TMS up to 18,000 rpm regarding hydration properties (65.0 ± 2.0% dm and 66.5 ± 0.3% dm, respectively). Consequently, mechanical forces are the main factor controlling the structural modification and functional properties of flours during grinding.

Diamond enriched lamination and winding insulation for electrical machines

2019 ◽  
Vol 38 (4) ◽  
pp. 1245-1252
Author(s):  
Aron Szucs ◽  
Zlatko Kolondzovski ◽  
Jan Westerlund ◽  
Juha Vahala
Keyword(s):  
Thermal Conductivity ◽  
Thermal Management ◽  
System Analysis ◽  
Electrical Machines ◽  
Production Costs ◽  
Electrical Machine ◽  
Paradigm Change ◽  
Electrical Insulator ◽  
Content Type ◽  
Winding Insulation

Purpose The thermal management of electrical insulations poses a challenge in electrical devices as electrical insulators are also thermal insulators. Diamond is the best solid electrical insulator and thermal conductor. This can lead to a paradigm change for electrical machine winding and lamination insulation design and thermal management. The paper introduces these techniques and discusses its effect for the design of electrical machines and its potential consequences for electromagnetic analysis, for example, in multi-physics modelling. The diamond winding insulation is patent-pending, but the diamond enriched lamination insulation is published for the benefit of the scientific community. Design/methodology/approach The windings of electrical machines are insulated to avoid contact between the coil and other conductive components, for example, the stator core. The principle of using mica tape and resin impregnation has not changed for a century and is well established to produce main insulation on a complex conductor shape and size. These insulations have poor heat-conducting properties. Similarly, the insulation of laminated steel sheets comprising the stator and rotor restrict heat flow. Diamond-based insulation provides a new path. Increased thermal conductivity means reduced temperature rise and the reduced thermal time constants in multi-physics simulations and system analysis. Findings The largest benefit of a diamond-based core insulation is in electrical machines in which the losses are conducted axially to the coolant. These are machines with radial ducts and effective cooling in the end regions. The main benefit will be in reducing the number of radial ducts that positively affect the size, production costs and the copper losses of the machine. The increased thermal conductivity of the diamond insulation system will reduce the thermal constants noticeably. These will affect system behavior and the corresponding simulation methods. Originality/value Diamond insulation can lead to a paradigm change for electrical machine winding and lamination insulation design and thermal management. It might also lead to new modeling requirements in system analysis.

Numerical Modeling of Dynamic Processes of the Reciprocating Reversible Electrical Machine

2015 ◽  
Vol 792 ◽  
pp. 134-142
Author(s):  
Igor Vladimirovich Ivshin ◽  
Andrey Michailovich Kopylov ◽  
Alfred Robertovich Safin
Keyword(s):  
Numerical Modeling ◽  
Internal Combustion Engines ◽  
Permanent Magnets ◽  
Electric Machines ◽  
Electrical Machines ◽  
Design Parameters ◽  
Electrical Machine ◽  
Operating Cycle ◽  
Stator Windings ◽  
Linear Electric Machine

Now rotational electrical machines are used mainly for the implementation a reciprocating motion of working mechanisms and also as the electric generators powered by internal combustion engines. It is achieved by means of the kinematic transfers complicating a design and reducing the drive efficiency. The use of linear reciprocating electric machines allows to eliminate these defects. It should be noted that the most effective ones are the cylindrical designs of reciprocating electric machines with permanent magnets, whose efficiency reaches 93 – 95%. However, the rarity and lack of a mass production of this machine type and special recommendations for their design causes the need of research, directed on search of optimum constructive decisions. The article describes the types of linear electrical machines and summarizes the results of numerical modeling of dynamic characteristics for the three versions of the reciprocating cylindrical machine with permanent magnets of 10 kW with the oscillation frequency of the translator 20 Hz and the length of operating cycle of 120 mm. The most effective design parameters of linear electric machine were determined on the basis of its specific characteristics and analysis of the EMF graphics shape, appearing on the stator windings in the generator mode.

scholarly journals Reliability-Oriented Design of Inverter-Fed Low-Voltage Electrical Machines: Potential Solutions

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4144
Author(s):  
Yatai Ji ◽  
Paolo Giangrande ◽  
Vincenzo Madonna ◽  
Weiduo Zhao ◽  
Michael Galea
Keyword(s):  
Power Density ◽  
High Speed ◽  
High Performance ◽  
Low Voltage ◽  
Electrical Machines ◽  
Design Stage ◽  
Switching Frequency ◽  
Special Focus ◽  
Electrical Machine ◽  
Engineering Approach

Transportation electrification has kept pushing low-voltage inverter-fed electrical machines to reach a higher power density while guaranteeing appropriate reliability levels. Methods commonly adopted to boost power density (i.e., higher current density, faster switching frequency for high speed, and higher DC link voltage) will unavoidably increase the stress to the insulation system which leads to a decrease in reliability. Thus, a trade-off is required between power density and reliability during the machine design. Currently, it is a challenging task to evaluate reliability during the design stage and the over-engineering approach is applied. To solve this problem, physics of failure (POF) is introduced and its feasibility for electrical machine (EM) design is discussed through reviewing past work on insulation investigation. Then the special focus is given to partial discharge (PD) whose occurrence means the end-of-life of low-voltage EMs. The PD-free design methodology based on understanding the physics of PD is presented to substitute the over-engineering approach. Finally, a comprehensive reliability-oriented design (ROD) approach adopting POF and PD-free design strategy is given as a potential solution for reliable and high-performance inverter-fed low-voltage EM design.

scholarly journals Ceramic-like Composite Systems for Winding Insulation of Electrical Machines

2020 ◽  
Author(s):  
Soren Miersch ◽  
Ralph Schubert ◽  
Thomas Schuhmann ◽  
Uwe Schuffenhauer ◽  
Markus Buddenbohm ◽  
...  
Keyword(s):  
Electrical Machines ◽  
Composite Systems ◽  
Winding Insulation

scholarly journals The Impact of Thermal Degradation on Properties of Electrical Machine Winding Insulation Material

2016 ◽  
Vol 52 (4) ◽  
pp. 2951-2960 ◽  
Author(s):  
Malgorzata Sumislawska ◽  
Konstantinos N. Gyftakis ◽  
Darren F. Kavanagh ◽  
Malcolm D. McCulloch ◽  
Keith J. Burnham ◽  
...  
Keyword(s):  
Thermal Degradation ◽  
Electrical Machine ◽  
Insulation Material ◽  
Winding Insulation ◽  
The Impact

scholarly journals Effciency of an Electrical Machine in Electric Vehicle Application

2016 ◽  
Vol 11 (1) ◽  
pp. 20-29 ◽  
Author(s):  
S. B. Shah ◽  
B. Silwal ◽  
A. Lehikoinen
Keyword(s):  
Electric Vehicle ◽  
Standard Method ◽  
Operating Cost ◽  
Electrical Machines ◽  
Electrical Machine ◽  
Test Machine ◽  
Current Component ◽  
Element Analysis ◽  
Voltage Drops ◽  
Wide Range

Machines have always made life simpler, directly or indirectly. They have been developed for a very wide range of applications. For the per- formance analysis of any machine, one important parameter to be considered is the machine loss. This consideration has signifcances like determining the effciency of the machine which in turn infuences the operating cost, determining the heating of machine and for accounting the voltage drops or current component associated with the cause of the losses and many more. Losses in electrical machines can be categorized according to the causes or phenomena that produce them. The effciency of an electrical machine directly depends on different kind of losses in the machine. Therefore, in this paper we primarily focus on the losses in the machine. First, all possible losses, their causes and effects in an electrical machine have been explained. A brief account of calculating those losses has also been explained. The standard method of calculating the effciency follows after that. Finally, a fnite element analysis is performed for a test machine and the losses and the effciency of the test machine is stud- ied. Journal of the Institute of Engineering, 2015, 11(1): 20-29 

scholarly journals Modeling of Losses Due to Inter-Laminar Short-Circuit Currents in Lamination Stacks

2013 ◽  
Vol 3 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Sahas Bikram Shah ◽  
Paavo Rasilo ◽  
Anouar Belahcen ◽  
Antero Arkkio
Keyword(s):  
Boundary Layer ◽  
Short Circuit ◽  
Tangential Component ◽  
Electrical Machines ◽  
Electrical Machine ◽  
Induced Current ◽  
Layer Model ◽  
Boundary Layer Model ◽  
Fine Mesh ◽  
Additional Losses

Abstract The cores of electrical machines are generally punched and laminated to reduce the eddy current losses. These manufacturing processes such as punching and cutting deform the electrical sheets and deteriorate its magnetic properties. Burrs are formed due to plastic deformation of electrical sheets. Burr formed due to punching on the edges of laminated sheets impairs the insulation of adjacent sheet and make random galvanic contacts during the pressing of stacked sheets. The effect of circulating current occurs if the burrs occur on the opposite edges of the stacks of laminated sheets and incase of bolted or wielded sheets, induced current return through it. This induced current causes the additional losses in electrical machine. The existence of surface current on the boundary between two insulated regions causes discontinuity of tangential component of magnetic field. Hence, based on this principle, the boundary layer model was developed to study the additional losses due to galvanic contacts formed by burred edges. The boundary layer model was then coupled with 2-D finite element vector potential formulation and compared with fine mesh layer model. Fine mesh layer model consists of finely space discretized 950028 second order triangular elements. The losses were computed from two models and were obtained similar at 50 Hz. The developed boundary layer model can be further used in electrical machines to study additional losses due to galvanic contacts at the edges of stator cores.

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