Mario Mezzarobba
University of Trieste
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Mario Mezzarobba.
IEEE Transactions on Industry Applications | 2012
F. Luise; Stefano Pieri; Mario Mezzarobba; Alberto Tessarolo
Some high-torque electric machines, such as low-speed wind generators, may be very difficult to test on load because of the large and expensive mechanical equipment required to load them (motors) or to drive them (generators). In this paper, a full-load regenerative testing methodology is described which does not require any rotating equipment to be coupled to the machine where the rated active power flows in a closed loop between the machine and a suitably connected dual-stage converter. The successful application of this methodology to a 780-kW 14-r/min wind generator prototype is addressed as a study case. Relevant experimental results are reported in a companion paper.
international conference on electrical machines | 2014
C. Bruzzese; Alberto Tessarolo; Mario Mezzarobba; Mauro Bortolozzi; D. Zito; T. Mazzuca; L. Piva
A fault-tolerant machine used for safety-critical tasks must a) guarantee at least a reduced-performance operation in case of partial machine fault and b) guarantee avoidance of drive mechanical jam/stall in case of total machine fault, to allow for the intervention of the back-up systems. Classical hydrostatic transmissions used on board ships for critical tasks such as rudder and stabilizing fin steering gears fulfill both the requirements a), b) above, but recent proposals for substitution with full-electric drives (rotary motors coupled with multistage reduction gears) usually do not. Especially the requirement b) needs particular attention and increased complexity when dealing with geared drives. This paper proposes a linear permanent-magnet direct drive fulfilling both the requirements above, for (but not limited to) rudder/fin steering gears. The absence of gears grants the requirement b), whereas the full-modular structure satisfies a), with independently fed stator modules and multiple inverters. This paper addresses some fault scenarios including electrical failures, in the machine winding (short-circuited coils) and in the inverters (trip of one or more units). The performance degradation is studied and assessed for the cases considered by both simulations and measurements on a prototype.
IEEE Transactions on Industry Applications | 2012
F. Luise; Stefano Pieri; Mario Mezzarobba; Alberto Tessarolo
The on-load factory testing of high-power electric machines may be a challenge due to the large mechanical equipment required to drive or load them. In a companion paper, a regenerative full-load testing strategy has been proposed, where the power flows in a closed loop between the electric machine and a dual-stage converter so that only the power corresponding to system losses needs to be supplied by the test facility and no mechanical equipment is needed. In this paper, the implementation of such testing strategy on a 780-kW 14-r/min permanent-magnet alternator with fractional-slot concentrated stator winding is described. Test results are presented and compared with the predictions made in Part I, showing a satisfactory accordance between theoretical and experimental results.
IEEE Transactions on Magnetics | 2015
Alberto Tessarolo; Mario Mezzarobba; Roberto Menis
Spoke-type interior permanent magnet (IPM) machines are an attractive topology for high-performance electric motors, especially designed for vehicle traction applications. In this paper, a special design for a spoke-type IPM motor is presented to enhance motor flux-weakening capability in the operation over a wide speed range. The proposed design consists of a simple and robust mechanical device that includes radially displaceable rotor yokes, connected to the shaft by means of springs. At high speed, the centrifugal force prevails over the elastic one due to springs, causing the mobile yokes to displace radially and establish a partial magnetic short circuit between PMs. This increases PM leakage flux and consequently reduces the air-gap field. As a result, a mechanical flux weakening effect is achieved at high speed, which helps significantly to reduce the demagnetizing d-axis current to be injected by the inverter, along with the related copper losses and demagnetization issues. The proposed design is investigated in this paper using an analytical model whose parameters are computed by finite-element analysis. The effectiveness of the solution being set forth is successfully proven by some testing on a laboratory prototype. Experimental results are compared with analytical predictions showing a satisfactory accordance.
electrical systems for aircraft, railway and ship propulsion | 2012
Roberto Menis; Mario Mezzarobba; Alberto Tessarolo
Permanent-magnet synchronous motors are widely used in vehicular traction applications due to their high efficiency and torque density. A critical point of their operation is the flux weakening needed at high speed, which usually implies injecting a d-axis demagnetizing current by the inverter. This paper presents a critical survey of the alternative approaches found in the literature and patent databases to enhance flux-weakening performance by acting on motor mechanical and electromagnetic design.
international conference on electrical machines | 2010
Alberto Tessarolo; Mario Mezzarobba; Alfredo Contin
In three-phase induction machines, the non-sinusoidal winding distribution normally causes space harmonics in the air-gap field, with negative impacts on stray-load losses and parasitic torques. An appropriate coil pitch choice is a traditional design strategy to improve the air-gap field waveform. In this paper an alternative technique is investigated based on using stator coils with unequal size. The proposed method does not affect the machine manufacturing process except for requiring two differently sized stator coil types. The effectiveness of the methodology is assessed both analytically and by mean of finite-element analysis, with a good accordance between the results independently obtained in the two ways.
electrical systems for aircraft, railway and ship propulsion | 2012
Alberto Tessarolo; F. Luise; Mauro Bortolozzi; Mario Mezzarobba
In electric permanent-magnet motors for traction applications, an open slot stator design is to be used when the winding is composed of flat-turn coils. The open slot design, combined with rotor permanent magnets, can produce remarkable cogging torque effects. This paper describes a magnetic wedge design which allows for a significant cogging torque reduction and, at the same time, allows for a fine adjustment of stator phase inductance values. The new wedge concept is applied in the paper to a 12-slot surface permanent-magnet motor. Finite-element analysis is used to study the wedge design effects on motor phase inductance and cogging torque amplitude.
conference of the industrial electronics society | 2016
Alberto Tessarolo; Mario Mezzarobba; Nicola Barbini
Fractional slot windings based on concentrated tooth coils are frequently used in todays electric machines. A drawback of these windings is the occurrence of large space harmonics in the air gap, which can cause torque ripple issues and rotor additional losses. Various provisions have been proposed in the literature to improve the air-gap harmonic content due to concentrated-winding armature reaction. This paper proposes an enhancement based on a multiple-layer design characterized by tooth coils with different number of turns. The improvement is proposed for 12-slot 10-pole permanent magnet machines but can be generalized to other possible topologies. It is shown that the proposed approach leads to the same air-gap field harmonic content as for a dual-three-phase dual-layer winding with all space harmonics reduced by the same coefficient (equal to 0.928). Pros and contras of the proposed design with respect to other existing improved solutions are highlighted in the paper. Comparisons and assessments are provided based on Finite Element Analysis (FEA).
international conference on ecological vehicles and renewable energies | 2014
Alberto Tessarolo; Mario Mezzarobba; Roberto Menis
In many applications, electric machines are designed for operation over a wide speed range and require important flux weakening capabilities at high speeds. This paper presents and innovative rotor mechanical design that endows an interior permanent magnet (IPM) machine with an intrinsic capability of reducing its own rotor flux at high speeds. Unlike most state-of-the-art flux-weakening techniques, the design does not involve any additional current source nor demagnetization currents to be injected into stator circuits. It relies on a purely mechanical device that establishes a partial magnetic short circuit between rotor permanent magnets. The device is able to self-activate by centrifugal force when the speed exceeds a given threshold that can be fixed by design. The paper presents criteria for dimensioning the new IPM rotor and a mathematical model to predict its performance. The proposed solution is implemented into a motor prototype whose manufacturing and testing are discussed for experimental validation.
electrical systems for aircraft, railway and ship propulsion | 2012
Alberto Tessarolo; F. Luise; Mario Mezzarobba; Mauro Bortolozzi; Lorenzo Branz
Permanent magnet synchronous machines, especially if designed with open stator slots, may suffer from important cogging torque issues. A special magnetic wedge design has been presented in a companion paper to cope with this problem. The design of such wedge is herein processed through a genetic algorithm in order to find the optimal configuration, which leads to cogging torque minimization. An optimal design configuration is found and compared to non-optimal ones to quantify the benefits that can be achieved by genetic optimization.