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Claudio BIANCHINI

Ricercatore t.d. art. 24 c. 3 lett. B presso: Dipartimento di Ingegneria "Enzo Ferrari"


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Pubblicazioni

2021 - Improvement on Flux Weakening Control Strategy for Electric Vehicle Applications [Articolo su rivista]
Bianchini, Claudio; Franceschini, Giovanni; Torreggiani, Ambra
abstract

This paper proposes an optimized flux weakening (FW) control strategy for interior permanent-magnet synchronous electric motor to address the critical issues that could occur under torque setpoint transition in flux weakening region, due, for example, to an emergency braking. This situation is typical in electric vehicles where the electrical machines operate over a wide speed range to reach high power density and avoid gearboxes. Two modified traditional flux weakening strategies are proposed in this paper to improve torque control quality during high speed torque transition. The proposed modified control strategies were validated both by Matlab/Simulink simulations, modeling the power train of a light vehicle application, and extensive experimental tests on a dedicated test bench.


2020 - Design of low-cost synchronous machine to prevent demagnetization [Articolo su rivista]
Bianchini, C.; Torreggiani, A.; Davoli, M.; Bellini, A.
abstract

The request for high efficiency motor paves the way for the replacement of induction motors with permanent magnet synchronous motors. Although the efficiency is increased, for medium and high power, the current ripple causes significant additional losses in the magnet and lamination; and, high temperature can lead to demagnetization. In this paper, a new rotor topology is proposed and compared to a traditional surface permanent magnet rotor to reduce the magnet losses and protect them from demagnetization. A reference surface permanent magnet machine is compared with the proposed one in terms of performance and magnet losses. Both analytical and experimental analysis are carried out and discussed.


2020 - Design of motor/generator for Flywheel Batteries [Articolo su rivista]
Bianchini, Claudio; Torreggiani, Ambra; David, Danilo; Bellini, Alberto
abstract


2020 - Fault Tolerance Analysis of a Ironless PM Machine for Energy Storage [Relazione in Atti di Convegno]
Bianchini, C.; Torreggiani, A.; David, D.; Davoli, M.; Bellini, A.
abstract

Energy storage is an emerging technology that can enable the transition towards renewable-energy-based distributed generation, reducing peak power demand and the time difference between production and use.Energy storage can be implemented both at grid level or at user level and nowadays different technologies are available for this purpose. Chemical batteries represent the de facto standard of storage systems for performance and maturity, however, chemical batteries feature a quite large environmental footprint and use precious raw materials.Mechanical storage technologies could be a viable alternative, because of their reduced impacts on the environment and on the exploitation of raw materials. Mechanical storage technologies require a motor/generator as an interface between the flywheel, the grid and a renewable energy source. In this paper a custom machine based on an ironless surface permanent-magnet structure is compared with iron core structures, with special reference to fault tolerance. In fact, the electrical machine shall work either as a motor or as a generator and it is the enabler for some critical specifications: high-discharge duration and compatible size/dimension. For this application, high rejection of faults is an important option, that requires an efficient fault detection system and a fault tolerant configuration. The proposed solution is based on the ironless dual-rotor surface permanent-magnet machine that is perfectly suited for these specifications. The ironless dual-rotor configuration features two main advantages: (1) the phases are magnetically and electrically isolated; (2) reactive components are much lower than resistive components. In addition, the ironless machine topology is less sensitive to unbalanced air gap radial forces that arise during fault operations due to a non symmetrical air gap magnetic field. These forces would strongly affect magnetic or air bearings, that are a mandatory option to reduce mechanical losses and to increase discharge duration. Hence, the proposed ironless structure is the best suited for the energy storage application.In this paper three synchronous electrical machines are modeled and compared via finite element analysis and a prototype of the dual-rotor ironless machines was realized and tested.


2020 - Slot design optimization for copper losses reduction in electric machines for high speed applications [Articolo su rivista]
Bianchini, C.; Vogni, M.; Torreggiani, A.; Nuzzo, S.; Barater, D.; Franceschini, G.
abstract

The need of a wide operating range and a high power density in electric machines for fulland hybrid electric vehicles in traction applications has led to an increase in the operating frequency of the machine. When the electric frequency increases, the additional losses in stator windings become an issue and they have to be taken into account in the design of the electric machine. This issue is more critical when hairpin windings are employed, due to the the skin and proximity effects which produce increased copper losses. In this paper, the relationships between different stator slot parameters (tooth width, slot opening, etc.) and stator winding copper losses have been analysed in order to identify an optimal design of a single stator slot.


2019 - Demagentization Issues in Low Cost Synchronous Machine [Relazione in Atti di Convegno]
Bianchini, C.; Torreggiani, A.; Davoli, M.; David, D.; Bellini, A.; Formentini, A.
abstract

The request for high efficiency motor opens the possibility of substituting induction motors with more efficient permanent magnet synchronous motors. For medium and high power, the current ripple causes significant additional losses in the magnet and lamination and correlated demagnetization issues of the rotor permanents magnets due to high temperature. In this paper a new rotor topology is proposed and compared to a traditional surface permanent magnet rotor to reduce the magnet losses and protect them from demagnetization. A reference surface permanent magnet machine is compared with the proposed one in terms of performance and magnet losses. Both analytical and experimental analysis are carried out and shown in the following.


2019 - Design for reliability: The case of fractional-slot surface permanent-magnet machines [Articolo su rivista]
Torreggiani, A.; Bianchini, C.; Davoli, M.; Bellini, A.
abstract

Surface permanent-magnet machines are widely used in different applications, from industrial automation to home appliance and electrical traction. Among any possible machine topology, the fractional-slot surface permanent-magnet one has gained increasing importance, because of its high torque density, low cogging torque, extended flux weakening capability and high efficiency. In addition, fractional-slot machines are attractive for tooth concentrated windings, which allow some optimized manufacturing solutions such as modular stator tooth and high slot filling factor, which result in copper volume reduction; cost reduction, and lower stator parasitic resistances. The slot-pole combination is one of the most important design parameter and, as shown in this paper, it affects performances and the robustness of the machine with respect to the manufacturing imperfections. In the literature, slot-pole combinations are optimized at design phase by finite-element analysis relying on a healthy machine model. The original contribution of this paper is a design for reliability method that models manufacturing defects and includes them at design phase in the optimization process of slot-pole combinations. A method is presented that allows defining the optimal design parameters for maximum performances and robustness towards unavoidable imperfections caused by tolerances of the manufacturing process.


2019 - Design optimization and analysis of a synchronous reluctance machine for fault-tolerant applications [Relazione in Atti di Convegno]
Babetto, C.; Bianchi, N.; Torreggiani, A.; Bianchini, C.; Davoli, M.; Bellini, A.
abstract

This paper deals with the design and optimization of a synchronous reluctance machine with dual three-phase winding for fault-tolerant applications. The target is to investigate several design solutions, in terms of winding arrangements and machine geometry, to achieve a good drive system reliability both in healthy and faulty conditions. The fault reliability is evaluated in terms of torque quality, unbalanced force and magnetic coupling between the healthy and the faulty three-phase winding. In the first part of the work, two different optimization strategies of the rotor geometry are proposed and an optimal solution is selected. In the second part, the performance of the selected individual are evaluated in several healthy and faulty operating conditions to investigate the reliability of the proposed design procedure.


2019 - Enhanced Internal Permanent-Magnet Machines Flux Weakening Control Strategies for Traction Applications [Relazione in Atti di Convegno]
Fornari, Raffaele; Franceschini, Giovanni; David, Danilo; Torreggiani, Ambra; Bianchini, Claudio; Frigieri, Matteo
abstract


2019 - Optimal Design and Experimental Validation of a Synchronous Reluctance Machine for Fault-Tolerant Applications [Relazione in Atti di Convegno]
Babetto, C.; Bianchi, N.; Torreggiani, A.; Bianchini, C.; Davoli, M.; Bellini, A.
abstract

In this paper a dual-three phase synchronous reluctance machine is optimized for fault-tolerant applications. The main objective of such a design is improving the fault-tolerant capability by means of a proper motor geometry and winding arrangement paying attention to the torque density, torque ripple, mutual magnetic coupling and the maximum short circuit currents in several operating conditions. Finally, a prototype is manufactured and tested in order to validate the simulation predictions yielding good results.


2019 - Stator fault diagnosis by reactive power in dual three-phase reluctance motors [Relazione in Atti di Convegno]
Bianchini, C.; Torreggiani, A.; Davoli, M.; Bellini, A.; Babetto, C.; Bianchi, N.
abstract

Electrical machines are wide spread because of their intrinsic robustness, versatility and reduced impact on energy and resources. Recently, the demand has focused on specific features: compatibility with power converters and fault tolerance. In fact, a wide range of applications require variable speed drives and high rejection of faults, i.e. safe operation also for non-critical applications. Here, a dual three-phase stator configuration is used, and a novel method for stator fault detection is presented. This method is based on reactive power measurements from both three-phase systems. A differential diagnostic index is defined, that can be used to detect effectively stator faults, isolating them from torque oscillations, load unbalances or other pitfalls.


2018 - Ironless Dual-Rotor Permanent-Magnet Machine for Flywheel Batteries [Relazione in Atti di Convegno]
David, D; Bianchini, C; Torreggiani, A; Bellini, A
abstract

Energy storage is an emerging technology that can enable the transition towards renewable-energy-based distributed generation, reducing peak power demand and the time difference between production and use.The energy storage could be implemented both at grid level or at user level and nowadays different technologies are available for this purpose. In particular chemical batteries represent the de facto standard of storage systems for performance and maturity, however batteries feature a quite large environmental footprint and use precious raw materials. As an alternative to chemical batteries, mechanical storage technologies could be evaluated because of their reduced impacts on the environment and on the exploitation of raw materials. This paper presents the design, the prototyping and the experimental results of an ironless surface permanent-magnet (SPM) synchronous machine for a flywheel energy storage at household level. The electrical machine can work either as a motor or as a generator and it is the main item to fulfill the major challenges of a household application: high discharge duration and compatible size/ dimension. The performance of the proposed ironless SPM machine are also compared with traditional iron core SPM synchronous machine by means of Finite Element Analysis (FEA).


2018 - Reduction of Torque Ripple in Synchronous Reluctance Machines through Flux Barrier Shift [Relazione in Atti di Convegno]
Ferrari, S.; Pellegrino, G.; Davoli, M.; Bianchini, C.
abstract

Synchronous Reluctance (SyR) machines are a viable alternative to other kinds of electrical machines in many fields. The simple rotor structure allows a high efficiency level with low manufacturing costs and higher safety in high-speed operations. However, one of the main problems of the SyR machines is the torque ripple generated by the interaction of the stator and rotor Magneto-Motive Force harmonics. Many design solutions have been proposed to date, but heavy torque ripple reduction has only been achieved with long optimizations runs or with complex machine structures. This paper presents an easy and effective method to reduce torque ripple through flux barrier shift. Two machines were designed in order to compare the proposed design with a state-of-the-art procedure. The machines designed with flux barrier shift presents similar performances to the optimized machine, with a lower design time and a more general design method.


2017 - CSI7: a Modified Three-phase Current Source Inverter for Modular Photovoltaic Applications [Articolo su rivista]
Lorenzani, Emilio; Immovilli, Fabio; Migliazza, Giovanni; Frigieri, Matteo; Bianchini, Claudio; Davoli, Matteo
abstract

This paper analyzes the performance of a gridtied, wide power range, transformerless, modified threephase Current Source Inverter (CSI), named CSI7. The CSI7 topology is here analyzed along with a suitable Space Vector Modulation (SVM) strategy able to attenuate the excitation of the output CL filter. The theoretical analysis and simple analytic expressions highlighted the performance and limitations of the topology when employed as a singlestage PV inverter, with particular emphasis on injected grid currents distortion and ground leakage current values. The inverter wide input range allows interfacing PV strings of different module count with a simple closed loop control. The principle of operation and control is described, the viability of the CSI7 topology was assessed with simulations and extensive experiments on a full-size laboratory prototype.


2017 - Ground leakage current in PV three-phase current source inverter topologies [Relazione in Atti di Convegno]
Lorenzani, E.; Migliazza, G.; Immovilli, F.; Bianchini, C.; Buticchi, G.
abstract

Current source inverter (CSI) is a family of power converters which has been recently investigated for photovoltaic power conversion in grid-tied operation, due to the inherent boost capability and ease of control. This paper assess Photovoltaic three-phase Current Source Inverters by two different CSI topologies and space vector modulation commutation strategies. Different CSI solutions are therefore analyzed by means of numerical simulations and the results are compared in terms of ground leakage current and THD of the injected grid currents. Extensive simulation results show that the CSI7 topology can improve the common mode performance while at the same time increasing the efficiency of the conventional CSI, at the price of a negligible added complexity.


2017 - Parametric Design Method for SPM Machines Including Rounded PM Shape [Relazione in Atti di Convegno]
Lu, C; Ferrari, S; Pellegrino, G; Bianchini, C; Davoli, M
abstract

Surface-mounted permanent magnet (SPM) machine is widely applied in industry application because of its high torque density, high efficiency and simple rotor structure. This study presents a parametric design plane, which makes the desired machine performance visualized during the machine design process. Based on that, a new parametric design method is introduced to simplify the design procedure of SPM motors. Besides the standard radial PM shape, the presented method applies to magnets of modified shape called "rounded", intended for torque ripple minimization at no additional manufacturing cost and such as stator skewing, rotor stepping or the like. The design flowchart for the method is illustrated and the output designs are validated by finite element analysis (FEA) and experimental tests. The proposed design method is embedded in a machine design instrument available online.


2016 - A design method to reduce pulsating torque in PM assisted synchronous reluctance machines with asymmetry of rotor barriers [Relazione in Atti di Convegno]
Davoli, Matteo; Bianchini, Claudio; Torreggiani, Ambra; Immovilli, Fabio
abstract

In this paper a design method for ferrite assisted synchronous reluctance machine is proposed in order to reduce torque ripple and cogging torque. An asymmetrical layout of the rotor flux barriers is proposed in order to reduce the harmonics components of the pulsating torque. The proposed analytical method is validated, employing finite elements simulations, for pure synchronous reluctance (SyR) and permanent magnet assisted synchronous reluctance machines (PMSyR) considering different slot-pole configurations. Simulated machines present a cogging torque and a torque ripple reduction respectively up to 92% and up to 70%. Moreover the electromotive force waveform is improved too. These results are achieved without reducing nominal torque and without increasing machines production costs.


2016 - Ground leakage current reduction in single-phase current source inverter topologies [Relazione in Atti di Convegno]
Migliazza, Giovanni; Lorenzani, Emilio; Immovilli, Fabio; Bianchini, Claudio
abstract

This paper presents a grid-tied single phase photovoltaic microinverter based on Current Source Inverter (CSI) topology. The main topic of this work is related to the identification of a topology and a PWM strategy able to minimize the obvious issues of the basic CSI solution: efficiency and ground leakage current. The strong reduction of this last issue allows the use of the proposed solution in conjunction with Photovoltaic module in building integrated installations. Simulation results and a low voltage experimental validation present the effectiveness of the proposed solution in mitigating ground leakage currents.


2015 - Active Rectifier With Integrated System Control for Microwind Power Systems [Articolo su rivista]
Buticchi, Giampaolo; Lorenzani, Emilio; Immovilli, Fabio; Bianchini, Claudio
abstract

This paper presents simple and effective control strategies for the active rectifier stage (AC/DC stage) of a grid-connected low power system for micro wind applications employing Permanent Magnet Synchronous Generator (PMSG). In particular a novel algorithm for the estimation of the rotor angle of the PMSG, based on flux estimators, was implemented using an adaptive low-pass filter coupled with a feed-forward compensator. This enabled a very smooth start-up operation of the PMSG, obtained by pre-loading the values of the flux estimator and using a single voltage transformer (VT) transducer. The solution for the power flow control between the active rectifier and the other(s) power converters connected to the common DC link was implemented without any digital communication between them, in order to obtain a solution suitable for modular architectures (e.g. to be used in conjunction with a grid-connected converter and/or an energy storage system). Simulation and experimental results confirmed the effectiveness of the proposed solutions. The experimental validation was conducted using a grid-connected converter as load for the proposed active rectifier.


2015 - Evaluation of combined reference frame transformation for interturn fault detection in permanent-magnet multiphase machines [Articolo su rivista]
Immovilli, Fabio; Bianchini, Claudio; Lorenzani, Emilio; Bellini, Alberto; Fornasiero, Emanuele
abstract

This paper focuses on modeling and experimental validation of a diagnostic fault classification procedure for interturn fault detection in permanent-magnet (PM) multiphase machines designed for fault-tolerant electric drives. The diagnostic procedure is based on the symmetrical component theory and relies upon the combined space vector D that gathers information from the two original space vectors obtained with different reference frames. The diagnostic index effectiveness and robustness were also investigated against other fault types such as rotor eccentricities and magnet damage to assess its discrimination capability. The proposed procedure was experimentally evaluated for the interturn fault case on a five-phase PM machine. Experiments were carried out at different speed and load levels, with increasing numbers of short-circuited turns. Both simulation and experimental results demonstrated the feasibility of the proposed diagnostic method.


2015 - Low cost PM synchronous servo-applications employing asynchronous-motor frame [Relazione in Atti di Convegno]
Bianchini, Claudio; Davoli, Matteo; Pellegrino, Gianmario; Immovilli, Fabio; Lorenzani, Emilio
abstract

This paper presents a comparison among low cost permanent magnet synchronous machine (PMSM) solutions, employing the frame and the stator laminations of an asynchronous machine. The comparison is carried out by means of finite element simulations. This work aims at obtaining machines with reduced cost, competitive in terms of nominal torque, torque ripple and cogging torque. The baseline for comparison is a surface mounted PMSM with high-strength magnets and non-skewed rotor. In order to reduce torque ripple and cogging torque, magnets with sinusoidal profiles radial wise are first introduced. Second, enhanced hybrid permanent magnets poles are adopted, replacing part of high strength NdFeB material with cheaper ferrite to reduce the production costs of the magnetic pole. Finally these PMSMs are compared to a synchronous reluctance and ferrite-assisted synchronous reluctance machines. The presented results indicate that the hybrid-magnets solution is the best trade-off between performance, cost and manufac-turability and that the ferrite-assisted synchronous reluctance machine is quite competitive and low cost.


2014 - Design optimization for torque ripple minimization and poles cost reduction with hybrid permanent magnets [Relazione in Atti di Convegno]
Bianchini, Claudio; Davoli, Matteo; Immovilli, Fabio; Lorenzani, Emilio
abstract

This paper presents design strategies for the optimized design of the rotor poles in synchronous permanent magnet machines. The strategies are aimed at the reduction of torque ripple and cogging torque. Sinusoidally rounded magnet and rotor step-skewing are investigated, then a new proposal to reduce the cost of magnetic pole made in rare earth is presented. The goal is to introduce into a rotor pole, a fraction of low cost ferrite magnets on either side of the main rare earth NdFeB permanent magnet. The design procedure begins with some analytical consideration that allows to optimize the geometrical design of the magnets. Using Finite Element (FE) simulations, the effectiveness of the analytical model is verified and the results of the various methods are compared.


2014 - Enabling technologies for a fault tolerant linear actuation drive [Relazione in Atti di Convegno]
Buticchi, G.; Galea, M.; Empringham, L.; De Lillo, L.; Gerada, C.; Bianchini, C.
abstract

In safety critical applications, such as for the aerospace industry, where fault tolerant systems are mandatory, the ability of an electric actuator to detect a malfunctioning and eventually operate in faulty conditions is of paramount importance. This paper is concerned with the fault tolerance operation of a linear actuation drive, consisting of a tubular, linear motor controlled and driven by a high performance matrix converter for an aerospace application. The aim of this work is thus to propose and validate techniques addressing specific faulty operation conditions. The main points of interest addressed in this paper are the operation of the position sensor and operation during a fault on one of the phases of the motor. An Extended Kaiman Filter is adopted for the double goal of improving the measured data of the position sensor and to continuously monitor its condition. On the other hand, the TLPM motor is operated under the assumption of a total fault of a single phase. In this work the modification to the Field Oriented Control (FOC) with only two phases is described, and the results are compared to those of the healthy machine. Theoretical analysis, simulations and experiments confirms the feasibility of the described strategies.


2013 - Axial Flux Permanent Magnet Machine Desing and Optimization Using Multi Layer 2D Simulation [Relazione in Atti di Convegno]
Bianchini, Claudio; Immovilli, Fabio; Lorenzani, Emilio; A., Bellini; L., Felici
abstract

This paper presents the design of an axial flux permanent magnet machine for in-wheel application. The machine design and optimization are developed using two-dimensional (2-D) multi-layer finite element analysis approach. The threedimensional model of the machine has been approximated with a set of simulations in which the two-dimensional geometrical parameters were varied appropriately in order to reproduce the actual three-dimensional magnetic behavior. During design optimization, special attention was paid to the reduction of flux linkage harmonic content and to the reduction of cogging torque through the change of the permanent magnet profile and dimensions. Finally, a prototype machine was built to validate the effectiveness of the proposed method.


2013 - Bearing fault model for induction motor with externally induced vibration [Articolo su rivista]
Immovilli, Fabio; Bianchini, C.; Cocconcelli, Marco; Bellini, Alberto; Rubini, Riccardo
abstract

This paper investigates the relationship between vibration and current in induction motors operated under external vibrations. Two approaches are usually available to define this relationship. The former is based on airgap variations, the latter on torque perturbation. This paper is focused on the airgap variations model. The ball bearing fault is modeled by contact mechanics. External vibrations often occur in many industrial applications where external induced vibrations of suitable amplitude cause cyclic radial loading on the machine shaft. The model is validated by experiments, thanks to a dedicated test setup, where an external vibration source (shaker) was employed, together with ball bearing alterations in order to decrease the stiffness of the support along radial direction. To maximize the effects of externally induced vibrations, the frequency chosen was near the flexural resonance of the rotor (determined by FEM analysis). The direction of the external vibration is radial with respect to the axis of the electric machine under test. During tests, both stator phase currents and vibration of the machine were sampled. The test setup allowed to vary machine speed and load, vibration amplitude and bearing stiffness (damage level). Radial effects are usually visible only in case of large failures that result in significant airgap variations, as confirmed by experiments


2013 - Experimental Evaluation of Combined Reference Frames Transformation for Stator Fault Detection in Multi-Phase Machines [Relazione in Atti di Convegno]
Bianchini, Claudio; Immovilli, Fabio; Lorenzani, Emilio; Bellini, Alberto; E., Fornasiero
abstract

This paper focuses on the modeling and experimental validation of a diagnostic index for fault detection in multiphase machines. Experiments are carried out on of a five-phase permanent-magnet machine designed for fault tolerant applications. The diagnostic index is aimed at stator faults detection and is based upon the combination of information from two different reference frames. The diagnostic index effectiveness and robustness are assessed by Finite Element analysis and experiments.


2013 - Performance Analysis of a Modified Current Source Inverter for Photovoltaic Microinverter Applications [Relazione in Atti di Convegno]
Lorenzani, Emilio; Immovilli, Fabio; Bianchini, Claudio; A., Bellini
abstract

This paper analyzes the performance of a grid-tied photovoltaic module integrated, transformerless, three-phase Current Source Inverter (CSI). The design exploits CSI inherent step-up capability to obtain a single stage power interfacing between the low voltage PV input and the high AC voltage output, to be fed into the distribution grid. A modified CSI converter topology is proposed along with a suitable PWM strategy and a simple closed loop control. The theoretical analysis and simple analytic expressions highlighted the performance and limitations of the topology when employed in single-stage PV microinverter supplied by a single low voltage PV panel. The principle of operation and control is described, and the traditional CSI topology has been simulated numerically in Matlab/Simulink environment. Results obtained with the proposed topology are presented and evaluated in order to validate the theoretical assumptions.


2013 - Power Losses Analysis in Interleaved Flyback Based PV Grid Connected Micro-Inverters [Relazione in Atti di Convegno]
Causo, Alberto; Salati, Andrea; Lorenzani, Emilio; Immovilli, Fabio; Bianchini, Claudio
abstract

This paper analyzes the power losses of photovoltaic micro-inverters based on flyback topology. A double secondary winding flyback converter topology was considered to inject alternating current into the grid. The purpose of this work is the identification and quantification of the different power losses present in a simple flyback topology and in the interleaved version with two different control strategies. The power losses comparison was carried out after designing a 250 W power converter using commercial, low cost components. Simulations in Matlab/Simulink environment highlighted the effectiveness of the interleaved architecture.


2012 - Dynamic Modeling of Double Cage Induction Machines for Diagnosis of Rotor Faults [Relazione in Atti di Convegno]
Lorenzani, Emilio; Salati, Andrea; Bianchini, Claudio; Immovilli, Fabio; Bellini, Alberto; Lee, S. B.; Yoo, J.; Kwon, C.
abstract

Double cage induction motors are typically employed in applications that require high starting torque for frequent, loaded starts. This makes the starting (outer) cage susceptible to fatigue failure since it must withstand the large thermo-mechanical stress associated with the high starting current and long acceleration time. Conventional FFT-based spectrum analysis techniques are insensitive to outer cage faults due to the small outer cage current under steady state operation, and the fault indicators and thresholds applied to single cage rotors cannot be used. Therefore, there is a strong industrial need for research and development of analysis techniques and advanced fault detection algorithms for double cage machines. However, there are only a few publications that investigate double cage rotor faults. In this paper, a dynamic model for rotor cage faults in double cage motors, which is the first step towards double cage rotor fault research, is derived. A 7.5 Hp separate end ring fabricated copper double cage rotor is built for experimental verification of the proposed fault model (copper inner cage/brass outer cage). The tests performed under startup and steady state operation show that the proposed fault model can provide sufficient accuracy and can be used as the basis for interpretation of FFT results and development of advanced fault detection algorithms.


2012 - Micro Wind Turbine System Integration Guidelines PMSG and Inverter Front End Choices [Relazione in Atti di Convegno]
Bianchini, Claudio; Immovilli, Fabio; Lorenzani, Emilio; Bellini, Alberto; G., Buticchi
abstract

This paper is aimed at the modeling and simulation of wind power system, with particular emphasis on small wind turbines employing surface permanent magnet synchronous gen- erators (SPMSGs). Generator and inverter front-end interaction is analytically and numerically modeled, in order to evaluate the generator’s efficiency depending on its electric parameters, both during normal and power limited operation. Passive and active rectifier front-end are taken into account to assess the influence of power electronics front-end over system performances. The final target of this work is to determine design guidelines for small wind turbine system optimization. The analysis is carried out through simulations which take into account the interactions of the SPMSG’s electrical parameters and through the evaluation of the generator’s efficiency at different operating conditions and inverter front-end architectures. The data obtained was further validated with experimental characterization of two different system architectures.


2012 - Optimal System Control of a Back-to-Back Power Converter for Wind Grid-Connected Converter [Relazione in Atti di Convegno]
G., Buticchi; Lorenzani, Emilio; Bianchini, Claudio
abstract

The most common topology for micro wind turbine systems is composed of the wind turbine directly connected to a Permanent Magnet Synchronous Generator (PMSG) followed by a AC/DC/AC converter. The converter is realized with a AC/DC passive rectifier, a DC/DC boost converter and a DC/AC full-bridge inverter which injects the electric power into the grid. Considering the cost reduction of power switches and Digital Signal Processors (DSP), back-to-back inverter topologies have to be considered for new projects, since they allow to obtain better energy productivity of the wind systems. In this paper a complete solution based on back-to-back topology is presented. This solution includes the sensorless vector control for the PMSG, the Maximum Power Point Tracker (MPPT) algorithm, the d-q vector control of the single-phase grid connected inverter and the power flow control strategies from the PMSG to the grid. It is worth noticing that the two full-bridge power converters are controlled by two different DSP which can exchange information only through the value of the DC Link voltage. Experimental results confirm the effectiveness of the adopted solutions.


2012 - Review of Design Solutions for Internal Permanent Magnet Machines Cogging Torque Reduction [Articolo su rivista]
Bianchini, Claudio; Immovilli, Fabio; Lorenzani, Emilio; Bellini, Alberto; Davoli, M.
abstract

Internal permanent magnet synchronous machinesare spreading in industrial production.They feature high torque density and extended speed rangethat are key issues in many fields of applications, however theircogging torque is typically quite high.Many methods and design guidelines for cogging torquereduction exist in literature and this paper compares them. Forthis purpose, the different design guidelines are applied to acommon reference machine in order to assess their effectiveness.Computer Finite Element Analysis (FEA) are carried out for eachcase in order to compare the cogging torque reduction capabilityof the different techniques. The side effects of these techniques,such as back-emf and rated torque profile distortions, willbe taken into account. The paper contribution is to comparethe various cogging torque reduction techniques and magneticgeometries on a common reference machine to identify the mosteffective ones.


2011 - A test bench for accelerated thermal ageing of III–V concentration solar cells using forward bias injection [Relazione in Atti di Convegno]
Immovilli, Fabio; Bianchini, Claudio; Bellini, Alberto; Sala, A.
abstract

Power production from solar photovoltaic systems is constantly increasing. In the last few years concentration photovoltaic (CPV) system using III-V multijunction cells appeared on the market, promising doubled efficiencies compared to traditional silicon PV solar panels. For CPV systems to be competitive on the market, they must be reliable to assure long-term operation. This paper presents the design and construction of a test bench for thermal cycling characterization of dense array receivers employing III-V multijunction cells mounted on a microchannel heat sink. Instead of a climatic chamber, the proposed test bench employs forward bias injection (FBI) to heat the cells, in order to better mimic on-field operating conditions. The experimental results of the accelerated ageing test are coherent with preliminary on-field trials, with a good agreement on the fault mechanism.


2011 - Currents and Vibrations in Asynchronous Motor with Externally Induced Vibration [Relazione in Atti di Convegno]
Immovilli, Fabio; Bianchini, C.; Cocconcelli, Marco; Bellini, Alberto; Rubini, Riccardo
abstract

This paper presents an experimental investigation ofthe airgap variation model for vibration and current harmonicsrelationship in induction motors. To this aim, an external vibrationsource was employed, together with ball bearing alterationsin order to decrease stiffness. The direction of the externalvibration is radial with respect to the axis of the electricmachine under test. To maximize the effect of externally inducedvibrations, the frequency chosen was near the flexural resonanceof the rotor, determined by FEM analysis.During tests both currents and vibration of the machine wereacquired. The test rig allowed to vary speed, vibration level andbearing stiffness. An electromagnetic brake provided a variableoutput load for the electric machine. The focus of the paper isthe review of fault models used in literature. Radial effects areusually visible only in case of large failures that result in air-gapvariations, as the experiments confirmed


2011 - Fault Detection of Linear Bearings in Brushless AC Linear Motors by Vibration Analysis [Articolo su rivista]
Bianchini, C.; Immovilli, F.; Cocconcelli, M.; Rubini, R.; Bellini, A.
abstract

Electric linear motors are spreading in industrial automation because they allow for direct drive applications with very high dynamic performances, high reliability, and high flexibility in trajectory generation. The moving part of the motor is linked to the fixed part by means of linear bearings. As in many other electric machines, bearings represent one of the most vulnerable parts because they are prone to wear and contamination. In the case of linear roller bearings, this issue is even more critical as the rail cannot be easily fully enclosed and protected from environmental contamination, unlike the radial rotating bearing counterpart. This paper presents a diagnostic method based on vibration analysis to identify which signature is related to a specific fault


2011 - Homopolar Generators: an Overview [Relazione in Atti di Convegno]
Bianchini, Claudio; Immovilli, Fabio; Bellini, Alberto; Lorenzani, Emilio; C., Concari; M., Scolari
abstract

Homopolar generators are a particular class of electrical machines capable of generating DC current without the use of mechanical commutators or electronic rectifiers. This paper presents an overview of the typical configurations of homopolar DC machines. The paper focuses on generating operation, trying to assess the optimal configuration for a high efficiency generator. Among the possible solutions, a specific configuration which uses permanent magnets for the excitation field was chosen and built to perform a set of experiments.


2010 - Cogging torque reduction methods for internal permanent magnet motors: Review and comparison [Relazione in Atti di Convegno]
Bianchini, Claudio; Immovilli, Fabio; Bellini, Alberto; Davoli, Matteo
abstract

Internal permanent magnet synchronous machines are spreading in industrial production. High torque density and extended speed operation range are key issues in many fields of applications. Many methods and design guidelines for cogging torque reduction exist in literature and this paper compares them. To this aim, the different design guidelines are applied to a reference machine to assess their effectiveness. Computer FEA analysis are carried out for each case in order to compare the cogging torque reduction potential of the different techniques. Other side effects, such as b.e.m.f and torque quality will be taken into account. The paper contribution is to compare various techniques on a common ground (the reference machine) to identify the most effective ones. ©2010 IEEE.


2009 - Design of linear alternators for thermoacoustic machines [Relazione in Atti di Convegno]
Rossi, Andrea; Immovilli, Fabio; Bianchini, Claudio; Bellini, Alberto; Serra, Giovanni
abstract

This paper compares the available technologies for linear electromagnetic alternators and categorizes them in order to find the best solutions for the thermoacoustic based CHCP. Tubular oscillating permanent magnet actuator featuring SMC stator with a quasi-Halbach PM slider is analyzed and modeled theoretically. Here, a similar configuration is compared to other moving magnet structure but employing open modular construction with laminated magnetic steel winding cores and a critical comparison is made relying on electromagnetic and mechanical simulations to retrieve the best solution for the thermoacoustic application. © 2009 IEEE.


2009 - Fault Diagnosis of Linear Bearings in Brushless AC Linear Motors [Relazione in Atti di Convegno]
Bianchini, C.; Immovilli, Fabio; Cocconcelli, Marco; Rubini, Riccardo; Bellini, Alberto
abstract

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2009 - Fault diagnosis of linear electric generators for thermoacoustic machines [Relazione in Atti di Convegno]
Rossi, Andrea; Immovilli, Fabio; Bianchini, Claudio; Bellini, Alberto; Serra, Giovanni
abstract

Energy generation and its optimal use are key issues nowadays. In this framework the use of cogeneration (CHP) or trigeneration (CHCP) is an attractive solution towards higher system efficiency. Traditional thermal machines are used as a prime mover in a CHP/CHCP plant. Recently novel technologies were investigated for prime mover and cooler. Among them thermoacoustics is attractive as it allows to embed a prime mover, a cooler and an alternator in a single machine. Moreover, it features reduced maintenance cost as it requires no moving parts but the electric alternator. The design of an efficient electric alternator is one of the major challenge, as it must convert into electricity a small linear displacement of the mover at high frequency. The latter is a critical item in terms of diagnostics also. Here the fault diagnosis of a thermoacoustic generator is investigated, where the major defects are ageing or fatigue of the spring used to center and sustain the mover of electric generator. The fault diagnosis is based on the non invasive analysis of electric signals at the generator terminal. The paper also deals with post fault strategies. © 2009 IEEE.


2009 - Stator fault detection for multi-phase machines with multiple reference frames transformation [Relazione in Atti di Convegno]
Bianchini, C.; Fornasiero, E.; Matzen, T. N.; Bianchi, N.; Bellini, A.
abstract

The paper focuses on a new diagnostic index for fault detection of a five-phase permanent-magnet machine. This machine has been designed for fault tolerant applications, and it is characterized by a mutual inductance equal to zero and a high self inductance, in order to limit the short-circuit current. This paper defines a diagnostic index for stator fault detection based upon the combination of information from two different reference frames. Both analytical and simulation analysis are adopted to validate the new diagnostic index. The analytical results are currently being validated by experiments on a dedicated test bed. ©2009 IEEE.


2008 - Arc Linear Motors for Direct Drive Robots: Galileo Sphere [Relazione in Atti di Convegno]
Bianchini, Claudio; Immovilli, Fabio; P., Mignano; Bellini, Alberto
abstract

This paper presents the design of an arc linear motor for a new type of robot, named Galileo Sphere, based on direct drive technology for pick and place operations. Pick and place robots require high dynamics and position accuracy and repeatability. A classical implementation is based on rotating electric machines with reduction gearboxes and kinematic mechanisms that convert the rotating motion to linear where necessary.The direct drive technology reduce mechanical losses, backlash, MTBF and a number of components. This technology also achieves higher dynamic and accuracy.The robot has a polar-like configuration with 5 degree of freedom.A dynamical simulator was used to assess motors, that satisfies a typical pick and place trajectory with the different payload. The proposed solution resulted feasible, even at high working frequencies and with payloads up to 4 kg. The precisionand repeatability remained high, within 100 micron.The working is a spherical sector with 1870 mm maximum diameter, and 450mm vertical reach.


2008 - Comparative analysis of CHCP systems based on solar energy [Relazione in Atti di Convegno]
Immovilli, Fabio; Bellini, Alberto; Bianchini, Claudio; Rossi, Andrea; Franceschini, G.
abstract

The combined production of heating, cooling and electricity (CHCP) or trigeneration in a grid-connected energy market may become profitable with respect to traditional systems, where electricity, heat, and cooling are produced or purchased separately. Namely, the use ofsolar energy as a primary energy source can lead to a substantial improvement, overcoming many of the traditional drawback associated with micro-cogeneration and trigeneration.So doing a CHCP system with renewable energy sources is realized, that is an attractivesolution for domestic needs, provided that a cost-effective technical solution is available.This paper reviews and compares CHCP system and technologies based on solar energy.


2008 - Fault detection of a five-phase permanent-magnet motor [Relazione in Atti di Convegno]
Bianchini, Claudio; T., Matzen; E., Fornasiero; N., Bianchi; Bellini, Alberto
abstract

The paper focuses on the fault detection of a five-phase Permanent-Magnet (PM) machine. This machine has been de- signed for fault tolerant applications, and it is characterised by a mutual inductance equal to zero and a high self inductance, with the purpose to limit the short circuit current. The effects of a limited number of short-circuited turns were investigated by theoretical and Finite Element (FE) analysis, and then a procedure for fault detection has been proposed, focusing on the severity of the fault (i.e. the number of short- circuited turns and the related current).


2008 - Solar trigeneration for residential applications, a feasible alternative to traditional micro-cogeneration and trigeneration plant [Relazione in Atti di Convegno]
Immovilli, Fabio; Bellini, Alberto; Bianchini, Claudio; Franceschini, G.
abstract

Trigeneration stands for the combined production of electricity, heat, and cooling (CHCP).This paper reviews and compares CHCP system based on solar energy with respect to traditional CHCP ones.A further comparison is made among the possible technologies for solar CHCP to assess the technical solutions more suited to residential applications. Beyond photovoltaic based systems, two other solutions are proposed: a concentrated sunlight all-thermoacoustic system and an hybrid thermo-photovoltaic system.In a grid-connected energy market, the adoption of CHCP plants may become profitable with respect to traditional systems, where the single energies are produced or purchased separately. Specifically, the onset of solar trigeneration can lead to a substantial improvement, overcoming many of the traditional drawback associated with micro-cogeneration and trigeneration.The result is a trigeneration system based totally on renewable energy. This is especially attractive for the residential demand, provided that a cost-effective technical solution is available.