Stefano Nuzzo

About Stefano Nuzzo

Stefano Nuzzo, With an exceptional h-index of 20 and a recent h-index of 20 (since 2020), a distinguished researcher at Università degli Studi di Modena e Reggio Emilia, specializes in the field of Electrical Machines, Drives, Power Electronics.

His recent articles reflect a diverse array of research interests and contributions to the field:

An Asymmetrical Additively Manufactured Hairpin Winding for increased efficiency and sustainability

An integrated 2D/3D numerical methodology to predict the thermal field of electric motors

Optimal Sizing of Hairpin Conductors in highway operation with PWM power supply

Multi-objective Optimizations of Copper and Aluminum Hairpin Windings: a Comparison

Performance Analysis of a Permanent Magnet Motor with Continuous Hairpin Winding

Refined structural design and thermal analyses of a high-speed wound-field generator for the more electrical aircraft

Upgrade of Exciter for Synchronous Generators basing on the Hybrid Excitation Concept

Review and future developments of wound field synchronous motors in Automotive

Stefano Nuzzo Information

University

Università degli Studi di Modena e Reggio Emilia

Position

Research Fellow Italy & University of Nottingham

Citations(all)

1395

Citations(since 2020)

1248

Cited By

348

hIndex(all)

20

hIndex(since 2020)

20

i10Index(all)

35

i10Index(since 2020)

29

Email

University Profile Page

Università degli Studi di Modena e Reggio Emilia

Stefano Nuzzo Skills & Research Interests

Electrical Machines

Drives

Power Electronics

Top articles of Stefano Nuzzo

An Asymmetrical Additively Manufactured Hairpin Winding for increased efficiency and sustainability

Authors

Riccardo Notari,Stefano Nuzzo,Filippo Savi,Silvio Defanti,Davide Barater

Journal

IEEE Transactions on Transportation Electrification

Published Date

2024/3/7

Recently, hairpin windings (HWs) have been among the most studied and implemented winding topologies to enhance torque and power density of electrical machines (EMs), especially in the automotive sector. The aim of this work is threefold. First, it proposes an asymmetrical configuration for HWs, which exploits the possibility of reducing AC losses through the implementation of conductors featuring variable cross-section within the slot. Second, this asymmetrical winding is envisioned using additive manufacturing (AM), given the constraints imposed by the conventional manufacturing process of HWs. Third, a suitable aluminium (Al) alloy is selected as winding material, thus replacing copper (Cu), with the aim of achieving a more sustainable design. These three objectives are achieved through extensive analytical and numerical analyses and comparisons between conventional and asymmetrical windings, as …

An integrated 2D/3D numerical methodology to predict the thermal field of electric motors

Authors

Clara Iacovano,Fabio Berni,Giuseppe Cicalese,Stefano Nuzzo,Stefano Fontanesi

Journal

Case Studies in Thermal Engineering

Published Date

2024/4/1

The present work aims at providing a predictive numerical methodology for the thermal characterization of electric motors. The methodology relies on a 2D-FE simulation for the estimation of the electromagnetic (iron and joule) losses. The latter are then exploited in a 3D-CFD Conjugate Heat Transfer analysis for the evaluation of the thermal field.The CFD model includes both the solid components and the fluid domains. The main novelty of the paper is represented by the copper coil modelling. In fact, copper, air, epoxy resin and enamel are synthetized in a single homogeneous body able to reproduce the thermal behaviour without including the single components, to reduce the computational cost.The methodology is validated against experimental data on a three-phase squirrel-cage induction motor. As for the experimental data (available at three different operating conditions), temperature distributions are …

Optimal Sizing of Hairpin Conductors in highway operation with PWM power supply

Authors

R Notari,G Devito,F Bernardi,M Pastura,D Barater,S Nuzzo

Published Date

2023/4/13

Nowadays, one of the key challenges in the design of electric drives’ components is the reduction of high losses at high-frequency operations. The aim of this work is to investigate the AC losses in hairpin windings (HWs) triggered by a space vector pulse width modulation (SVPWM) during both maximum torque per Ampère (MTPA) and flux-weakening (F-W) operations of an interior permanent magnet synchronous motor (PMSM). The ensuing additional losses are evaluated and a fast methodology for the conductor sizing is illustrated. Subsequently, after evaluating the harmonic content of the current feeding the electric motor, estimated considering a standardized highway driving cycle, the losses are assessed using analytical and finite element methods (FEM) and then compared with an HW layout taken as benchmark. The results demonstrate that HWs, when appropriately sized, can significantly reduce AC …

Multi-objective Optimizations of Copper and Aluminum Hairpin Windings: a Comparison

Authors

Gregorio Cutuli,Stefano Nuzzo,Tianjie Zou,Giovanni Franceschini,Chris Gerada,Davide Barater

Published Date

2023/10/29

This work critically analyzes the possibility of adopting aluminum hairpin windings as alternative to copper in electric traction machines for automotive applications. Copper and aluminum hairpin winding solutions are compared based on two proposed scenarios. In the first one, the same winding Joule losses are kept, whereas in the second scenario the same machine volume is maintained. In both cases, copper and aluminum solutions are independently optimized through a Multi-Objective Genetic Algorithm, with the aim of reaching the required peak torque performance, while reducing the weight and the losses in specific drive conditions. For both analyzed scenarios, the optimal designs are compared in terms of weight/volume, costs, power losses and sustainability. Finally, a hybrid layout consisting in adopting both conductor materials in the same slot is proposed, thus achieving a reasonable trade-off solution …

Performance Analysis of a Permanent Magnet Motor with Continuous Hairpin Winding

Authors

Mohammad Soltani,Stefano Nuzzo,Davide Barater,Mauro Di Nardo

Published Date

2023/4/13

The global decarbonization targets require increasingly higher levels of efficiency, torque and power density, reliability, etc. of electrical machines intended for transport applications. Recently, hairpin windings are receiving more and more interest from both industry and academia, as they are a promising solution to achieve the above requirements altogether. However, a number of challenges still need to be addressed, including electromagnetic, thermal and manufacturing aspects. One of these is the reliability of the welding process, where the solution could be adopting continuous hairpin windings. However, these result in open slot designs or special stator arrangements, which can produce undesirable effects in motors, such as ripple torque, increased permanent magnet losses, etc. This paper aims at comparing the main electromagnetic performance metrics for a conventional hairpin winding, wound onto a …

Refined structural design and thermal analyses of a high-speed wound-field generator for the more electrical aircraft

Authors

A Guiducci,SG Barbieri,S Nuzzo,D Batater,F Berni,G Cicalese,S Fontanesi,G Franceschini

Published Date

2023/4/13

Wound-field synchronous machines are widely used as generators to cover the electric energy demands in various low-speed applications. The main advantages over their rare earth permanent magnet counterpart are the ease of control, the inherent fault tolerance, the low cost, the use of more sustainable materials, etc. However, permanent magnet machines are well known to provide higher power density and efficiency values, which make them the usually preferred choice as generator on board of aircraft. This is also enabled by the more robust structure of the rotor which allows operations at relatively high speeds. Contrarily, the rotor of the wound-field machine comprises salient poles, making it unsuitable for high-speed operations. This paper aims at investigating the structural and thermal performance of a high-speed wound-field generator for aircraft applications. The electromagnetic aspects, extensively …

Upgrade of Exciter for Synchronous Generators basing on the Hybrid Excitation Concept

Authors

Stefano Nuzzo,Valerio Arces,Paolo Bolognesi

Published Date

2023/7/17

In the classical brushless arrangement, the field current of wound-field synchronous generators (SGs) is provided by exciters through rotating diode rectifiers. The control of the SG field current is achieved indirectly by regulating the field current of the exciter, whose excitation winding is stationary. This paper investigates the possibility to equip the exciter with hybrid excitation by adding surface-mounted permanent magnets (PMs). While a hybrid PM - field winding exciter has already been proposed in a recent work, where the selected condition was the rated no-load operation of the SG, in this paper the PMs are designed to sustain the generating set (genset) operation at a suitably selected load condition. This permits to further reduce the excitation losses of the exciter and to operate the genset even in case of full failure in the exciter field system, including the related electronic controller.

Review and future developments of wound field synchronous motors in Automotive

Authors

Gaia Petrelli,Stefano Nuzzo,Tianjie Zou,Davide Barater,Giovanni Franceschini,Chris Gerada

Published Date

2023/3/29

Electric motors are increasingly spreading in the automotive sector, following the progressive electrification of transportation aimed to reduce CO 2 emissions and increase sustainability. Most of the employed motors are permanent magnets (PM) based and these materials are subjected to price fluctuations. In addition, they are not the key for sustainability, especially when referring to rare earth materials. An alternative to the classic PM motors is the wound field synchronous machine (WFSM) which, thanks to the absence of magnets, represents an inherent more sustainable solution. In addition, this machine presents higher controllability and fault tolerance compared to their PM counterpart, which on the other hand features higher torque density and efficiency values. While WFSMs have been widely adopted and studied as power generators in grid-connected and isolated power plants, their use as traction motors …

Potential of Powertrain Electrification in a mid-size Tractor for a more sustainable agriculture

Authors

Riccardo Sassetti,Simone Ferrante,Nicola Lenzini,Stefano Nuzzo,Stefano Fiorati,Davide Barater

Published Date

2023/7/17

Nowadays, global warming and emission regulations are leading manufacturers and scientific community interests towards off-highway vehicles electrification. This work provides potentials evaluation of powertrain electrification applied to a mid-size tractor. Modelling tools are exploited to perform simulations. Given the lack of standardized working cycles, field data measurements are exploited to build 6 different working cycles representative of specific tractor working conditions. A full hybrid series architecture with a thermostat control logic is investigated as a possible solution for a mid-size tractor. As result, a performance comparison is made between the traditional Internal Combustion Engine and the proposed electrified powertrain. Benefits are evaluated in terms of engine efficiency and fuel consumption.

AC losses analysis and design guidelines for hairpin windings with segmented conductors

Authors

Marco Pastura,Riccardo Notari,Stefano Nuzzo,Davide Barater,Giovanni Franceschini

Journal

IEEE Transactions on Transportation Electrification

Published Date

2023/3/9

In the last years, hairpin windings are amongst the most studied and implemented winding topologies to increase torque and power densities of electrical machines, especially in the traction field. However, their main drawback remains the elevated ohmic losses generated at high frequency operations. Recently, hairpin windings with segmented conductors have been proposed to overcome this challenge, but an analytical model to predict the losses in such unconventional winding is missing, as well as a critical analysis on the extra manufacturing complexities needed. In this paper, first a simple analytical formulation for the estimation of AC losses in segmented hairpin conductors is proposed, developed and validated at various operating frequencies, both through finite element analyses and experimental measurements. Then, an in-depth analysis of the main advantages and disadvantages of this winding …

Rare Earth Materials Reduction in a Hypercar Propulsion System

Authors

Giampaolo Devito,Francesco Puglisi,Davide Barater,Stefano Nuzzo,Mauro Giacalone,Giovanni Franceschini

Published Date

2023/7/17

Low-usage and rare earth free high-performance machines are in high demand, pushed by increasing costs and supply issues of rare earth materials. High torque density and high efficiency are key requirements in traction field. The challenge is designing propulsion systems which achieve such objectives while pursuing a global optimization logic in costs. This paper fits into this context by proposing a solution in which the same interior permanent magnet motor design is used for a four-wheel drive of a hypercar. A proper adaptation in axial length and magnets arrangement of the rear axle motor makes it suitable for the front axle requirements. Electromagnetic finite element analyses are performed to test different solutions with and without ferrite magnets. Torque, torque ripple, base speed, efficiency and rare earth reduction are the outputs under investigation. The best configurations are further studied via finite …

Preliminary Sensitivity Analysis and Optimisation of a Wound Field Synchronous Motor for Traction Applications

Authors

Gaia Petrelli,Stefano Nuzzo,Davide Barater,Tianjie Zou,Giovanni Franceschini,Chris Gerada

Published Date

2023/7/17

The automotive field is switching to electric propulsion to guarantee a more efficient and sustainable transportation. Several motor configurations can be adopted for this purpose. Permanent magnet-based motors are usually preferred, but they are the most expensive and the least sustainable, especially when rare-earth materials are employed. Wound Field Synchronous Motors (WFSMs) represent an interesting alternative for their reduced costs, excellent field controllability, acceptable torque performance and inherent fault tolerance. Most importantly, being a rare-earth free technology, they fit with the ever more stringent sustainability demands required by the automotive sector. The aim of this research is to highlight the influence that rotor design parameters of a traction WFSM have on the performance in terms of average torque and torque ripple. To this purpose, multi-objective optimisations are performed …

On the fault tolerance and PM demagnetisation of a high-performance aircraft propulsion motor

Authors

Ahmed Hebala,Stefano Nuzzo,Peter H Connor,Chris Gerada,Michael Galea

Published Date

2022/9/5

In this paper, a study of the fault-tolerance and demagnetisation of a high-performance aircraft propulsion motor is investigated. The motor is proposed with either three or four sets of three-phase windings, while maintaining the same magnetic and thermal design. The design and performance of each motor are evaluated and presented. A study on the performance of the motor in the case of a single-phase or a three-phase group loss is performed. Furthermore, the reduction in output power due to phase loss is compensated by an increase in the phase current scheme. Finally, the PM demagnetisation under severe fault and temperature conditions is considered. The results are validated through an FE transient simulation. The paper presents a robust motor design against faulty and severe operating conditions.

Output voltage overshoot suppression control for multilevel inverter architectures

Authors

Fabio Bernardi,Emilio Lorenzani,Filippo Savi,Stefano Nuzzo,Davide Barater

Published Date

2022/10/17

Wide-bandgap (WBG) power semiconductor devices have acquired more and more interest in power circuits, since they allow to operate at higher switching frequencies and temperatures compared to the conventional silicon-based devices, while also improving efficiency and power density. In electric drive applications they can produce significant electrical stress at the machine terminals due to their inherently elevated voltage gradients (dv/dt), hence resulting in a reduced lifetime of the entire system. Voltage overshoot at the electrical machine terminals depends on many factors, such as voltage dv/dt, cables type and length, electrical machines input impedance etc. In this paper, a novel control based on a recent multilevel drive architecture is presented. This control is able to minimize the voltage overshoot at the terminals of an electrical machine independently form the system layout, increasing the overall …

Combined magnet shaping and asymmetries in surface-mounted permanent magnet machines for improved torque performance

Authors

Giampaolo Devito,Stefano Nuzzo,Davide Barater,Mohammad Soltani,Giovanni Franceschini

Published Date

2022/9/5

Nowadays, the comfort standard required by vehicles are very stringent. Vibration and noise caused by cogging torque and torque ripple must be reduced. This paper analyzes the positive effects of combining magnets’ shaping techniques with asymmetric magnets’ placements on the torque ripple reduction of surface-mounted permanent magnet machines. An existing electrical machine designed for a racing car application is taken as a case study. A 2D finite element model is used and parametrized to accurately reproduce the existing design and compare its electromagnetic performance against other possible solutions. The same 2D finite element model is modified to analyze and compare asymmetric designs. General considerations are finally drawn, ensuing from very promising results being achieved when analyzing the combined effects of shaping and asymmetrically placing the magnets.

Analysis and Mitigation of AC Losses in High Performance Propulsion Motors

Authors

Ahmed Hebala,Stefano Nuzzo,Peter H Connor,Giuseppe Volpe,Chris Gerada,Michael Galea

Journal

Machines

Published Date

2022/9/7

In this paper, the AC copper losses in classical random windings are investigated and mitigated using several techniques across a range of permanent magnet synchronous motor designs. At high operating frequencies, AC copper losses can represent a substantial share of the total loss in electrical machines, thus, reducing the machine’s overall performance, and increasing the thermal loading. Recently, different approaches for modelling AC copper losses have been proposed. This paper utilises simulation software to quantify the expected AC losses in six different propulsion motor designs. The motor designs are then modified to reduce the AC winding losses through the implementation of five different methods. Using two-dimensional finite element analysis, the magnetisation direction, magnet to airgap ratio, copper stranding, magnetic wedges and the motor slot openings are modified to reduce AC losses. The paper considers distributed, fractional, slot and concentrated windings, and the results show promising reductions across these different winding configurations.

Investigation of the Temperature Effects on Copper Losses in Hairpin Windings

Authors

Mohammad Soltani,Stefano Nuzzo,Davide Barater,Giovanni Franceschini

Journal

Machines

Published Date

2022/8/20

Today, an extensive electrification is occurring in all industrial sectors, with a special interest seen in the automotive and aerospace industries. The electric motor, surely, is one of the main actors in this context, and an ever-increasing effort is spent with the aim of improving its efficiency and torque density. Hairpin windings are one of the recent technologies which are implemented onto the stator of the electric motor. Compared to conventional random windings, it inherently features lower DC resistance, higher fill factor, better thermal performance, improved reliability, and an automated manufacturing process. However, its bottleneck is the high ohmic losses at high-frequency operations due to skin and proximity effects (AC losses), resulting in a negative impact on the temperature map of the machine. Nevertheless, while it is well-known that DC losses increase linearly with the operating temperatures, the AC losses trend needs further insight. This paper demonstrates that operating the machine at higher temperatures could be beneficial for overall efficiency, especially at high-frequency operations. This suggests that a paradigm shift is required for the design of electric motors equipped with hair-pin windings, which should therefore focus on a temperature-oriented approach. In addition, the effect of the rotor topology on AC losses, which is often overlooked, is also considered in this paper. The combination of these effects is used to carry out observations and, eventually, to provide design recommendations. Finite element electromagnetic and thermal evaluations are performed to prove the findings of this research.

Analysis of voltage distribution and connections within a high-frequency hairpin winding model

Authors

Marco Pastura,Stefano Nuzzo,Davide Barater,Giovanni Franceschini

Published Date

2022/9/5

In the last years the adoption of hairpin windings is increasing, especially in the automotive sector, mainly due to their inherently high fill factor and electric loading capability.A critical aspect related to the reliability and lifetime of every winding typology is the voltage stress due to the uneven voltage distribution. This phenomenon has already been largely analyzed in conventional stranded conductors, while a few studies are available for hairpin windings. With the spreading of wide bandgap devices, the investigation on voltage distribution becomes an ever-timely topic due to their short rise times. This paper presents an analysis of the uneven voltage distribution triggered within hairpin windings by a low rise time waveform, using a complete high-frequency winding model. The different options to series-connect different paths are investigated, providing simple but essential guidelines to reduce the electrical stress …

A simplified analytical approach for hybrid exciters of wound-field generators

Authors

Giampaolo Devito,Stefano Nuzzo,Davide Barater,Giovanni Franceschini

Journal

IEEE Transactions on Transportation Electrification

Published Date

2022/4/18

Midpower wound-field generators are predominantly used for grid applications, marine naval ships, industrial buildings, and critical standby power applications. They are often equipped with brushless excitation systems (ESs), where an exciter supplies the generator through a diode rectifier. Here, the uncontrolled nature of the rectification process can determine a significant reduction of the mean value of the output voltage. Hence, the root causes must be identified and properly modeled for an accurate evaluation of the system performance. In this article, a simplified analytical model is proposed for such purposes, taking as case study a consequent-pole, hybrid exciter of a wound-field generator for naval applications. The approach is based on the calculation of the diodes’ commutation angle, which permits to estimate the exciter’s armature current waveforms. Special focus is given to the voltage waveforms, which …

On the AC losses in the end conductors of hairpin windings

Authors

Marco Pastura,Riccardo Notari,Stefano Nuzzo,Davide Barater,Giovanni Franceschini

Published Date

2022/9/5

In the last years, several resources have been employed to increase torque and power density values in electrical machines, especially in those intended for transport applications. In this context, the adoption of hairpin conductors is spreading thanks to their inherently high fill factor. Their main drawback is represented by their sensitivity to high-frequency phenomena, which can have a significant impact on the Joule losses and thus on the overall efficiency.While several researches have recently focused on ways to model and reduce such high-frequency losses in the slots, i.e. within the conductors’ active sides, a few data are available on their impact in the end winding regions.This work provides an investigation on the AC losses occurring in the end conductors of a hairpin winding traction motor. The losses are determined through 3D finite element simulations for a wide frequency range, and compared against …

See List of Professors in Stefano Nuzzo University(Università degli Studi di Modena e Reggio Emilia)

Stefano Nuzzo FAQs

What is Stefano Nuzzo's h-index at Università degli Studi di Modena e Reggio Emilia?

The h-index of Stefano Nuzzo has been 20 since 2020 and 20 in total.

What are Stefano Nuzzo's top articles?

The articles with the titles of

An Asymmetrical Additively Manufactured Hairpin Winding for increased efficiency and sustainability

An integrated 2D/3D numerical methodology to predict the thermal field of electric motors

Optimal Sizing of Hairpin Conductors in highway operation with PWM power supply

Multi-objective Optimizations of Copper and Aluminum Hairpin Windings: a Comparison

Performance Analysis of a Permanent Magnet Motor with Continuous Hairpin Winding

Refined structural design and thermal analyses of a high-speed wound-field generator for the more electrical aircraft

Upgrade of Exciter for Synchronous Generators basing on the Hybrid Excitation Concept

Review and future developments of wound field synchronous motors in Automotive

...

are the top articles of Stefano Nuzzo at Università degli Studi di Modena e Reggio Emilia.

What are Stefano Nuzzo's research interests?

The research interests of Stefano Nuzzo are: Electrical Machines, Drives, Power Electronics

What is Stefano Nuzzo's total number of citations?

Stefano Nuzzo has 1,395 citations in total.

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