Enrico Carraro

Traction PMASR Motor Optimization According to a Given Driving Cycle

Electric motors are ideal candidates for traction applications due to their optimal electromechanical characteristic, high efficiency, and manufacturing simplicity. Nowadays, the most attractive solutions are represented by the synchronous machines, due to the great advantages in terms of high performance and mass saving. Motor optimization is often performed in one or few operating points, usually located along the continuous or overload torque profile. On the other hand, the actual motor operation depends on the driving cycle of the vehicle, which might be different than the rated conditions. This paper deals with the design and optimization of a permanent-magnet-assisted synchronous reluctance motor according to two different duty cycles, one for city driving and another for mixed driving operation. A procedure is proposed to evaluate the most effective design areas by means of a series of representative points, which have been considered for the global optimization. The results and the advantages of the adopted methodology against the conventional procedure and optimized solutions are highlighted and discussed.

Selection Criteria and Robust Optimization of a Traction PM-Assisted Synchronous Reluctance Motor

In the coming years, the electrification and the deployment of the electric motors in the urban transports will become a more and more widespread reality. The optimization stage of the electric motors usually does not consider in detail the real driving conditions of the car in which the motor is installed. It follows that the actual motor performance in operating points, particularly as regards the torque ripple and the efficiency, might be worse than expected. A robust solution is a required target. This paper deals with the design and optimization of a high-speed permanent-magnet-assisted synchronous reluctance motor for traction applications, taking into account both city and highway driving cycles. A procedure is employed in order to evaluate the most representative operating points, which have to be considered when a global optimization is required. An analysis of the solution robustness has been performed. Both results and advantages of the adopted methodology are highlighted.

Electric Vehicle Traction Based on Synchronous Reluctance Motors

It was recently demonstrated that the synchronous reluctance motor is well suited for electric as well as for hybrid electric vehicles. This paper deeply investigates the capabilities of a synchronous reluctance motor and compares them with those of a permanent-magnet-assisted synchronous reluctance motor, according to the typical requirement of a traction application. A proper rotor design is necessary. The average torque is due to the rotor anisotropy. The permeance difference between the direct- and the quadrature-axis is achieved by means of a high number of flux barriers. The position of the flux barrier ends and proper rotor asymmetries are chosen so as to reduce the torque ripple, mainly due to the slot harmonics. The impact of the rotor design on the motor performance is presented deeply, showing several simulation and experimental results, carried out on synchronous reluctance motors with different rotor geometries. Permanent magnets can be inset in the flux barriers to assist the synchronous reluctance motor improving its capabilities, but avoiding to use rare-earth permanent magnets. The main advantages of the permanent magnet assistance is an increase of the main torque density and of the power factor. They are evaluated experimentally. However, the drawback of adopting permanent magnets is the possible demagnetization of the magnets themselves. This can greatly limit the maximum overload capability of the motor, which is a salient requirement of a traction motor.

Performance comparison of fractional slot concentrated winding spoke type synchronous motors with different slot-pole combinations

Fractional Slot Concentrated Winding (FSCW) Interior Permanent Magnet (IPM) synchronous motors are nowadays an attractive solution in automotive applications due to their important advantages in terms of high performance and manufacturing simplicity. Among the different topologies, the spoke type is an effective configuration when high torque density is required. On the other hand, the motor performance are heavily related to the selected slot-pole combination. This is a critical issue when there are high constraints in terms of torque quality, flux weakening performance and noise/vibration/harshness. This paper deals with the design and analysis of FSCW IPM spoke type motors, comparing eight optimal slot-pole combinations. Two different low cost PM typologies are considered. Design and optimization procedures, based upon a finite element analysis, are presented. The torque density, torque quality, electromechanical performance and deformation of the machines are compared, highlighting the advantages and the differences among the solutions.

Permanent magnet volume minimization of spoke type fractional slot synchronous motors

The combination of the spoke type interior permanent magnet synchronous motor together with the NdFeB is an effective solution when high torque density is required. On the other hand, in the last years, the instability and the high price of the rare earth make the magnet minimization and the optimization of the motor design critical and mandatory. This paper deals with the design criteria of a spoke type, fractional slot concentrated winding, interior permanent magnet motor, especially as regards the minimization of the magnet volume, maximization of the airgap flux density and optimization of the split ratio. An analytical procedure is presented and validated by means of finite element analysis. At last, the advantages and the differences among the solutions are highlighted.

Permanent magnet volume minimization in permanent magnet assisted synchronous reluctance motors

In the recent years the study on new motor topologies for automotive applications has found an increasing interest. The environmental impact of conventional internal combustion engine, together with the increasing demand and the cost of the oil, are two of the main reasons that makes electric motors an attractive alternative. Machines that employ interior permanent magnet configurations are widely recognized as good performance motors for traction applications. On the other hands, the exponential increase of the price of rare earths magnets in the last years, is making rare earth motors a very expensive solution. This encourage the research of low cost, rare earth free alternatives, represented by the permanent magnet assisted synchronous reluctance machines. Three different magnet dimension configurations have been considered. This research highlights the influence and benefits of the insertion of ferrite on the machine performance, emphasizing the importance of a careful evaluation of the magnet quantity in order to optimize the performance and reduce the total cost.

Optimization of a traction PMASR motor according to a given driving cycle

Electric motors are intrinsically ideal candidates for traction applications due the optimal electromechanical characteristics, high efficiency and manufacturing simplicity. Nowadays, one of the most attractive solutions is represented by synchronous machines, due to the great advantage in terms of high performance and mass saving. This paper deals with the design and optimization of a permanent magnet assisted synchronous reluctance motor, according to a given driving cycle. A procedure is proposed to evaluate the most effective design area, which has to be considered for the design and global optimization. Both results and advantages of the adopted methodology are highlighted.

Formula SAE electric competition: Electrical motor design

Electric mobility is becoming a growing reality due to increase of the demand and cost of oil and the environmental impact of conventional internal combustion engines. To follow this trend, national student competitions belonging to Formula SAE (Society of Automotive Engineers) series have been introduced for purely electric vehicles, in addition to those traditionally associated with internal combustion engine vehicles. On the other hand, the most promising and known electric motor candidates for traction application, represented by permanent magnet synchronous machines, are highly affected by the remarkable increase of the cost of rare earth magnet. For these reasons the research of rare-earth free alternatives, such as ferrite permanent magnet assisted synchronous reluctance motor, has potentially interesting implications especially in the perspective of industrial mass production. This paper shows the design criteria of ferrite permanent magnet assisted synchronous reluctance motors for a Formula SAE electric vehicle. The electromechanical performance have been evaluated and compared, in terms of torque and power. The most promising candidate has been finally compared with two equivalent size surface mounted permanent magnet machines: one is equipped with the same stator, while the second is characterized by a fractional slot concentrated winding. Finally, this research provides a brief description of the electric supply system in order to accurately and efficiently manage the motors for achieving the requested performance.

Robust optimization of a traction PMASR motor according to given driving cycles

In the coming years, the electrification and the deployment of the electric motors in the urban transports will become a reality more and more widespread. The optimization stage of the electric motors usually does not consider in detail the real driving conditions of the car in which the motor is installed. It follows that the actual motor performance in operating points, especially as regards the torque ripple and the efficiency, might be worsen than expected. A robust solution is a required target. This paper deals with the design and optimization of a high speed permanent magnet assisted synchronous reluctance motor for traction applications, according to both city and highway driving cycles. A procedure is employed in order to evaluate the most representative operating points, which have to be considered for the global optimization. An analysis of the robustness of the solutions has been performed. Both results and advantages of the adopted methodology are highlighted.

PM synchronous machine comparison for light electric vehicles

The research of rare-earth free alternatives, such as ferrite, hot pressed NdFeB Permanent Magnet Assisted Synchronous Reluctance (PMASR) motor or pure reluctance motor, has potentially interesting implications especially in the perspective of industrial mass production. This paper shows the comparison between a sintered NdFeB PMASR, ferrite PMASR, Synchronous Reluctance (REL) and a Surface mounted PM (SPM) machines with the same overall dimensions, winding arrangement and power supply size. The electromechanical performance have been evaluated and compared, in terms of torque and power. Finally, this research provides a description of the electric supply system in order to accurately and efficiently manage the motors for achieving the requested performance.