Alfredo Vagati

Bio: Alfredo Vagati is an academic researcher from Polytechnic University of Turin. The author has contributed to research in topics: Magnetic reluctance & Reluctance motor. The author has an hindex of 36, co-authored 98 publications receiving 4613 citations. Previous affiliations of Alfredo Vagati include Instituto Politécnico Nacional & University of Turin.

Performance Comparison Between Surface-Mounted and Interior PM Motor Drives for Electric Vehicle Application

Abstract: Electric vehicles make use of permanent-magnet (PM) synchronous traction motors for their high torque density and efficiency. A comparison between interior PM and surface-mounted PM (SPM) motors is carried out, in terms of performance at given inverter ratings. The results of the analysis, based on a simplified analytical model and confirmed by finite element (FE) analysis, show that the two motors have similar rated power but that the SPM motor has barely no overload capability, independently of the available inverter current. Moreover, the loss behavior of the two motors is rather different in the various operating ranges with the SPM one better at low speed due to short end connections but penalized at high speed by the need of a significant deexcitation current. The analysis is validated through FE simulation of two actual motor designs.

Comparison of Induction and PM Synchronous Motor Drives for EV Application Including Design Examples

Abstract: Three different motor drives for electric traction are compared, in terms of output power and efficiency at the same stack dimensions and inverter size. Induction motor (IM), surface-mounted permanent-magnet (PM) (SPM), and interior PM (IPM) synchronous motor drives are investigated, with reference to a common vehicle specification. The IM is penalized by the cage loss, but it is less expensive and inherently safe in case of inverter unwilled turnoff due to natural de-excitation. The SPM motor has a simple construction and shorter end connections, but it is penalized by eddy-current loss at high speed, has a very limited transient overload power, and has a high uncontrolled generator voltage. The IPM motor shows the better performance compromise, but it might be more complicated to be manufactured. Analytical relationships are first introduced and then validated on three example designs and finite element calculated, accounting for core saturation, harmonic losses, the effects of skewing, and operating temperature. The merits and limitations of the three solutions are quantified comprehensively and summarized by the calculation of the energy consumption over the standard New European Driving Cycle.

Design of low-torque-ripple synchronous reluctance motors

Abstract: A design approach oriented to the minimization of torque ripple is presented for synchronous reluctance motors of the transverse-laminated type. First, the possible types of rotors are classified and the more suited rotor structure is evidenced, to be matched to a given stator. Then, the inner rotor design is described, pointing out the low-ripple measures. Lastly, experimental results are given from three different rotors; they confirm the validity of the proposed approach.

Cross-Saturation Effects in IPM Motors and Related Impact on Sensorless Control

Abstract: Permanent-magnet-assisted synchronous reluctance motors are well suited to zero-speed sensorless control because of their inherently salient behavior. However, the cross-saturation effect can lead to large errors on the position estimate, which is based on the differential anisotropy. These errors are quantified in this paper as a function of the working point. The errors that are calculated are then found to be in good accordance with the purposely obtained experimental measurements

Design criteria of high performance synchronous reluctance motors

Abstract: The main problems related to the design of a synchronous reluctance servomotor are examined. The most suitable rotor structure is identified among different alternatives. A simplified but general algorithm is found for calculating the internal optimized anisotropy ratio. Optimization algorithms are given regarding minimization of the q-axis magnetic flux and maximization of torque for given outside diameter and power dissipation capability. A maximum torque design is illustrated in the general case, practical involvements of this design are pointed out and discussed. >

Power Electronics and Motor Drives in Electric, Hybrid Electric, and Plug-In Hybrid Electric Vehicles

Abstract: With the requirements for reducing emissions and improving fuel economy, automotive companies are developing electric, hybrid electric, and plug-in hybrid electric vehicles. Power electronics is an enabling technology for the development of these environmentally friendlier vehicles and implementing the advanced electrical architectures to meet the demands for increased electric loads. In this paper, a brief review of the current trends and future vehicle strategies and the function of power electronic subsystems are described. The requirements of power electronic components and electric motor drives for the successful development of these vehicles are also presented.

Pulsating torque minimization techniques for permanent magnet AC motor drives-a review

Abstract: Permanent magnet AC (PMAC) motor drives are finding expanded use in high-performance applications where torque smoothness is essential. This paper reviews a wide range of motor- and controller-based design techniques that have been described in the literature for minimizing the generation of cogging and ripple torques in both sinusoidal and trapezoidal PMAC motor drives. Sinusoidal PMAC drives generally show the greatest potential for pulsating torque minimization using well-known motor design techniques such as skewing and fractional slot pitch windings. In contrast, trapezoidal PMAC drives pose more difficult trade-offs in both the motor and controller design which may require compromises in drive simplicity: and cost to improve torque smoothness. Controller-based techniques for minimizing pulsating torque typically involve the use of active cancellation algorithms which depend on either accurate tuning or adaptive control schemes for effectiveness. In the end, successful suppression of pulsating torque ultimately relies on an orchestrated systems approach to all aspects of the PMAC machine and controller design which often requires a carefully selected combination of minimization techniques.

Automotive Electric Propulsion Systems With Reduced or No Permanent Magnets: An Overview

Abstract: Hybrid and electric vehicle technology has seen rapid development in recent years. The motor and the generator are at the heart of the vehicle drive and energy system and often utilize expensive rare-earth permanent magnet (PM) material. This paper reviews and addresses the research work that has been carried out to reduce the amount of rare-earth material that is used while maintaining the high efficiency and performance that rare-earth PM machines offer. These new machines can use either less rare-earth PM material, weaker ferrite magnets, or no magnets; and they need to meet the high performance that the more usual interior PM synchronous motor with sintered neodymium-iron-boron magnets provides. These machines can take the form of PM-assisted synchronous reluctance machines, induction machines, switched reluctance machines, wound rotor synchronous machines (claw pole or biaxially excited), double-saliency machines with ac or dc stator current control, or brushless dc multiple-phase reluctance machines.

Comparative Study of Interior Permanent Magnet, Induction, and Switched Reluctance Motor Drives for EV and HEV Applications

Abstract: With rapid electrification of transportation, it is becoming increasingly important to have a comprehensive understanding of criteria used in motor selection. This paper presents the design and comparative evaluation for an interior permanent magnet synchronous motor (IPMSM) with distributed winding and concentrated winding, induction motor (IM), and switched reluctance motor (SRM) for an electric vehicle (EV) or hybrid electric vehicle (HEV) application. A fast finite element analysis (FEA) modeling approach is addressed for IM design. To account for highly nonlinear motor parameters and achieve high motor efficiency, optimal current trajectories are obtained by extensive mapping for IPMSMs and IM. Optimal turn- on and turn- off angles with current chopping control and angular position control are found for SRM. Additional comparison including noise vibration and harshness (NVH) is also highlighted. Simulation and analytical results show that each motor topology demonstrates its own unique characteristic for EVs/HEVs. Each motor’s highest efficiency region is located at different torque-speed regions for the criteria defined. Stator geometry, pole/slot combination, and control strategy differentiate NVH performance.

A physically insightful approach to the design and accuracy assessment of flux observers for field oriented induction machine drives

Abstract: Rotor flux observers can provide an attractive means for achieving direct field oriented control of induction machines. This paper presents a physics-based design methodology and uses it to evaluate open-loop observers and to develop a new closed-loop flux observer. It is shown that the new flux observer is a straightforward structure with properties that combine the best features of known methods. A distinction is made between observers, which use only integration and feedback summation operations, and those estimation methods requiring approximate differentiation which are, in essence, "cancellation" methods. Furthermore, a clear distinction is made between accuracy and dynamic robustness of the observer. This distinction is important because the accuracy of flux observers for induction machines is inherently parameter sensitive, whereas robustness of observers, in a controls sense, is not parameter sensitive. Moreover, it is shown how flux observers can provide robust field oriented control because the flux angle is substantially more correct than the flux magnitude. A distinctive form of frequency response function (FRF) analysis similar to that used in classical control engineering is demonstrated to be a useful and insightful tool even though flux observers are multiple-input, multiple-output systems. Finally, the limits of such flux observers are experimentally evaluated. >