Uncertainty in the design space of electric machines
by Tim Miller of Motivity Ltd, Galashiels; University of Glasgow

Prof. Miller will begin with a humorous and somewhat philosophical review of uncertainty in engineering, together with numerous examples ranging from the simple to the advanced, including mathematical uncertainties and a discussion of tolerancing. The importance of measurement is emphasized throughout.

Insulation system design considerations and validation for higher voltage and inverter fed machines
by Ian Cotton of aHV Solutions

The use of higher voltages in aerospace and automotive applications challenges the use of conventional insulation systems – particularly where the voltage exceeds 800V DC. This presentation will explore the key issues that mean the designer has to take special care in the design of such high voltage insulation systems and the solutions that may be required in future platforms.

Inferior performance of electric motors caused by manufacturing-induced degradation of stator magnetic properties
by Lukasz Mierczak of Brockhaus

Accurate design and prediction of electric motor performance is not a trivial task. Motor design engineers make use of advanced numerical and analytical methods for electromagnetic and thermal analysis, and still find considerable differences in efficiency of modelled and manufactured machines. One of the primary sources for this mismatch is the inaccuracy in stator lamination magnetic properties, such as BH curve and power loss, which are used as input data for calculating flux linkages of the coils and heat dissipation, and consequently determining the main motor parameters including torque and operating temperature. Typically, the magnetic properties implemented in motor modelling are provided by the material supplier based on the Epstein frame measurements, according to the International Standard IEC 60404-2. The effects of processing of the magnetic materials during motor manufacturing are neglected which gives rise to uncertainty in prediction of motor performance. In this presentation the results from industrial case studies involving advanced magnetic measurements will be presented, including characterization of stress sensitivity of soft magnetic materials, optimization of stamping and stacking methods in production of stator cores, as well as evaluation of manufacturing technologies for mitigation of eddy current loss in permanent magnets. Moreover, the presentation will explore the direct correlation between the deterioration in magnetic properties and the inferior performance of EV IPM electric motor to emphasize the importance of maintaining the quality of stator cores to ensure optimal powertrain performance

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Voltage stresses in motor windings of inverter fed machines, their impact and mitigations
by Antonio Griffo of University of Sheffield

Power electronic converter-fed machines and drives are now ubiquitous in transport, renewable energy generations and industrial automation applications. Converters operating with pulse width modulated (PWM) waveforms produce voltage pulses at a high frequency and high voltage slew rate (high dv/dt) which can result in excessive voltage at the machine terminal and non-uniform voltage distribution within the machines windings. These voltage transients can significantly reduce the lifetime of the insulation of the connected machine/generator due to increased voltage overshoot, increased voltage across turns, phases and phase-to-ground, and higher frequencies. These will be exacerbated by the increased use of wide band-gap devices with fast-fronted voltage transients with dv/dt in excess of 10-30kV/us. In this talk, the effects of high frequency PWM voltages produced by fast-switching power electronic converters on voltage distributions in machine winding and insulation systems are analysed and characterised. Both high frequency oscillation modes due to the interaction of inverter, cables and machines, as well as a low frequency oscillation mode associated with the common mode impedance of machines, will be presented. Lifetime test results under partial discharges caused by high voltage slew rate will also be highlighted together with a number of mitigation measures.

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Characterisation of Stranded Random Windings and their Impact on AC losses of Electrical Machines
by Josh Hoole of Bristol University

The electrification of the automotive sector demands power dense and volume electric traction motors. These requirements lead to the adoption of stranded random windings. However, mass production results in significant variability in the sources of AC winding loss due to the random transposition of the strands within the winding. Such variability is rarely characterised leading to conservatism in machine design and the inability to accurately predict the long-term reliability of such windings. This presentation will cover recent work that aims to characterise the manufacturing variability in random windings and quantify the impact they have on electrical machine losses.

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Design of an Electric Motor Housing, concepts and challenges
by Red Blaylock of iNetic

The talk will focus on the design of an electric motor housing, first by introducing a couple of different housing concepts used in the automotive industry. The talk will then build on this by exploring different coolant concepts and challenges associated with each design.

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A chicken and egg problem – uncertainties in thermal design of electrical machines
by Rafal Worbel of Newcastle University

An appropriate thermal management is one of the key considerations when developing new or upgrading existing electrical machines. However, a reliable thermal design of electrical machines is very challenging, frequently requiring numerous redesign and hardware iterations. This results from inherent uncertainties associated with the thermal design process, where empirically derived data is usually needed. Consequently, to experimentally inform design of an electrical machine a legacy hardware (an electrical machine) is required. Hence, the thermal design of electrical machines is something of a chicken and egg problem. This presentation discusses selected sources of uncertainties related to thermal design of electrical machines. The subject matters included in the presentation are focused on, but not limited to the heat source distribution, equivalent material thermal properties, manufacturing and assembly factors, and application specific operating requirements.

Manufacturing effects on NdFeB laminated magnet and how designers can allow for these when designing motors
by Domenico Violante of Arnold Magnetic Technologies

High efficiency motor applications demand best materials and laminated magnets are proven to reduce eddy current losses. Fewer eddy current losses means lower heat and greater efficiency. Manufacturing techniques have a direct impact on NdFeB laminated magnet performance. In this presentation, different manufacturing techniques are examined, analyzing the effect of each of them on the demagnetization curve of the magnet. Based on this investigation, a finite element model of laminated magnet which considers the manufacturing effects is presented, with the aim of determining its demagnetization curve, which represents a key input parameter when designing motors using NdFeB laminated magnet.

Uncertainties and Opportunities of Hairpin Winding Development for High Performance Electric Vehicle Traction: From Manufacturing Perspective
by Tianjie Zou of PEMC Institute, University of Nottingham

Windings housed within stators of electrical machines are the “central pivot” of electromechanical energy conversion, operating at inherently higher temperatures due to DC and AC power losses, which to a large extent determine the motor’s power density level. The ever increasing requirements on power density and efficiency of electrical machines have prompted a revolution of winding technologies. Hairpin winding as an emerging winding solution based on advanced manufacturing, is a key enabler in gaining step-change performance improvements of machines in multi-physics domains, which makes it popular in electric vehicle traction. This presentation will start with introducing basic guideline of hairpin winding layout configuration by highlighting its “design for manufacturing” feature. Then, some dedicated analytical tools developed at research level will be discussed, which are aimed at rapidly addressing the uncertainties and flexibility in winding layout selection, power losses prediction, CAD modelling, as well as manufacturing. Finally, specific hairpin winding demonstrators developed and manufactured for 150kW and 400kW EV traction will be introduced.