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The linear induction motor is mainly adopted for traction or motion transmission applications. Some advantages of linear induction motors are: a direct electromagnetic thrust propulsion (no need of mechanical transmissions), low maintenance costs and precision linear positioning; on the other hand, this motor topology has low power factor and efficiency, longitudinal and transversal edge-effect. This paper proposes a novel fast simulation method to evaluate the performance and machine parameters of a double-sided linear induction motor via 2-D finite element analysis considering both a magnetic time-harmonic and magnetostatic problems. The thrust force is computed tuning the secondary aluminum plate resistivity as a function of the path length of the induced eddy currents due to the fundamental of the air gap magnetomotive force. The proposed method has been verified via several 2-D finite element simulations and validated with experimental tests.

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, the range of applications requires variable speed drives and high rejection of faults, i.e. safe operation also for non-critical applications.Here, a dual three-phase stator configuration for a synchronous reluctance motor is investigated. The power supply of the two three-phase system is independently regulated in order to reduce torque ripple compensating the current ripple via harmonic cancellation. The finite element analysis shows that a quite perfect compensation of the torque ripple can be achieved with a suitable displacement of the PWM carrier of the three-phase system supply.

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.

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.

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.

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.

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.

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.

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.

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.

This paper analyzes the performance of a grid-tied, wide power range, transformerless, modified three-phase current-source inverter (CSI), named CSI7. The CSI7 topology is here analyzed along with a suitable space vector modulation 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 single-stage photovoltaic (PV) inverter, with a particular emphasis on injected grid current 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.

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.

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.

Internal permanent-magnet synchronous machines are spreading in industrial production. They feature high torque density and ex- tended speed range that are key issues in many fields of applications, however their cogging torque is typically quite high. Many methods and design guidelines for cogging torque reduction exist in literature and this paper compares them. For this purpose, the different de- sign guidelines are applied to a common reference machine in order to assess their effectiveness. Computer finite element analysis (FEA) are carried out for each case in order to compare the cogging torque reduction capability of the different techniques. The side effects of these techniques, such as back-EMF and rated torque profile distortions, will be taken into account. The paper contribution is to compare the various cogging torque reduction techniques and magnetic geometries on a common reference machine to identify the most effective ones.

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.

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.