Electric Vehicles make use of permanent magnet synchronous traction motors for their high torque density and efficiency. A comparison between interior permanent magnet (IPM) and surface mounted permanent magnet (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 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 de-excitation current. The analysis is validated through finite-element simulation of two actual motor designs.Index Terms-Electric Vehicle, PM Synchronous motors, PM motor drives, Constant-power speed range, Iron loss, High speed AC drives. . Manuscript

This paper proposes and formalizes a comprehensive experimental approach for the identification of the magnetic model of synchronous electrical machines of all kinds. The identification procedure is based on controlling the current of the machine under test while this is driven at constant speed by another regenerative electric drive. Compensation of stator resistance and inverter voltage drops, iron loss, and operating temperature issues are all taken into account. A road map for implementation is given, on different types of hardware setups. Experimental results are presented, referring to two test motors of small size, and references of larger motors identified with the same technique are given from the literature.

Three different motor drives for electric traction are compared, in terms of output power and efficiency at same stack dimensions and inverter size. Induction motor, surface mounted permanent magnet (SPM) and interior permanent magnet (IPM) synchronous motor drives are investigated, with reference to a common vehicle specification. The induction motor is penalized by the cage loss but it is less expensive and inherently safe in case of inverter unwilled turn-off 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 the more complicated to be manufactured. Analytical relationships are first introduced and then validated on three example designs, 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 calculation of the energy consumption over the standard NEDC driving cycle.

Different types of electric vehicles (EVs) have been recently designed with the aim of solving pollution problems caused by the emission of gasoline-powered engines. Environmental problems promote the adoption of new-generation electric vehicles for urban transportation. As it is well known, one of the weakest points of electric vehicles is the battery system. Vehicle autonomy and, therefore, accurate detection of battery state of charge (SoC) together with battery expected life, i.e., battery state of health, are among the major drawbacks that prevent the introduction of electric vehicles in the consumer market. The electric scooter may provide the most feasible opportunity among EVs. They may be a replacement product for the primary-use vehicle, especially in Europe and Asia, provided that drive performance, safety, and cost issues are similar to actual engine scooters. The battery system choice is a crucial item, and thanks to an increasing emphasis on vehicle range and performance, the Li-ion battery could become a viable candidate. This paper deals with the design of a battery pack based on Li-ion technology for a prototype electric scooter with high performance and autonomy. The adopted battery system is composed of a suitable number of cells series connected, featuring a high voltage level. Therefore, cell equalization and monitoring need to be provided. Due to manufacturing asymmetries, charge and discharge cycles lead to cell unbalancing, reducing battery capacity and, depending on cell type, causing safety troubles or strongly limiting the storage capacity of the full pack. No solution is available on the market at a cheap price, because of the required voltage level and performance, therefore, a dedicated battery management system was designed, that also includes a battery SoC monitoring. The proposed solution features a high capability of energy storing in braking conditions, charge equalization, overvoltage and undervoltage protection and, obviously, SoC information in order to optimize autonomy instead of performance or vice-versa.

The paper introduces a Unified Direct-Flux Vector Control scheme suitable for sinusoidal AC motor drives. The AC drives considered here are Induction Motor, Synchronous Reluctance and synchronous Permanent Magnet motor drives, including Interior and Surface-mounted Permanent Magnet types. The proposed controller operates in stator flux coordinates: the stator flux amplitude is directly controlled by the direct voltage component, while the torque is controlled by regulating the quadrature current component. The unified directflux control is particularly convenient when fluxweakening is required, since it easily guarantees maximum torque production under current and voltage limitations. The hardware for control is standard and the control firmware is the same for all the motors under test with the only exception of the magnetic model used for flux estimation at low speed. Experimental results on four different drives are provided, showing the validity of the proposed unified control approach.

The high speed operation region of Interior Permanent Magnet motor drives is investigated, with particular attention to the maximum torque per voltage operation. A technique is proposed for the control of the drive in such region, based on direct-flux field oriented vector control. The proposed control is easy to implement, does not require the accurate knowledge of the motor model and showed to be robust toward the effects of iron losses, of position estimation errors and dc-link variations. Moreover, it is suitable for operation in the inverter overmodulation range. Experimental results are provided for a 600 W IPM drive for home appliances.

This paper presents the direct flux control of an interior permanent-magnet (IPM) motor drive in the field-weakening region. The output torque is regulated by the coordinated control of the stator flux amplitude and the current component in quadrature with the flux, and it is implemented in the stator flux reference frame. The control system guarantees maximum torque production taking into account voltage and current limits, in particular in case of large dc-link variations. The field-oriented control does not necessarily require an accurate magnetic model of the IPM motor, and it is able to exploit the full inverter voltage at different dc-link levels with no additional voltage control loop. The feasibility of the proposed control method is investigated in discrete-time simulation, then tested on a laboratory rig, and finally implemented on board of an electric scooter prototype. The motor under test is an IPM permanent-magnet-assisted synchronous reluctance machine, with high-saliency and limited permanent-magnet flux. Index Terms-Direct flux control, motor drives control, synchronous motor drives, variable-speed drives, wide speed range. Gianmario Pellegrino (M'06) received the M.Sc.

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.