Multipolar SPM machines for direct drive application: a comprehensive design approach

A closed-form, per-unit formulation is proposed, for the design of surface mounted permanent magnet motors with high number of poles. The model evaluates the shear stress, the power factor and the specific Joule loss as the indicators of the machine performance, and demonstrates that this is determined by the correct choice of a very limited set of key-geometrical parameters. The design criteria are described analytically and then applied to example designs, FEA validated. Distributed- and concentrated-winding configurations are considered. The conclusions of the paper are consistent with the literature and aim to give a roadmap for designers of PM machines in modern applications, such as wind power synchronous generator

Reduced--cost Permanent Magnet mottor drives: a comprehensive design procedure and a universall approach to the magnettiic modell identification and conttol

This research deals with the design, identification and control of Permanent Magnet Synchronous motor drives. Throughout the project, motor and control designs have been straightly integrated in order to meet the challenging requirements, typically coming from the industrial world. Namely, the purposes leading this research activity are: cost-reduction and standardization of both design and control tasks into straightforward and universal procedures. As a deeper insight, this work proposes a comprehensive procedure for the design of reduced-cost Permanent Magnet based electrical machines and a universal control technique, requiring minimum calibration and a simplified preliminary commissioning stage. The recent price volatility of rare earth raw materials has been compelling designers and manufacturers of electric motors to find out or re-evaluate alternative machine topologies, using either a reduced amount of such rare-earth magnets or lower energy density magnetic materials, such as hard ferrites, still providing for high-performance technologies. This thesis is about facing this issue, while enhancing general approaches to the optimal design of Permanent Magnet Synchronous machines via fully-analytical models showing a twofold purpos

Comparison of Induction and PM Synchronous motor drives for EV application including design examples

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 Cycl

Performance comparison between Surface Mounted and Interior PM motor drives for Electric Vehicle application

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 design

Permanent Magnet minimization in PM-Assisted Synchronous Reluctance motors for wide speed range

This paper presents a technique to modify the rotor lamination of a permanent-magnet-assisted synchronous reluctance motor, in order to reduce the magnet volume with no side effect on performance. A closed-form analysis, which is based on a lumped parameter model, points out that the magnet quantity can be minimized with a significant saving of material volume and cost. At a second stage, the risk of demagnetization is evaluated since the minimized magnets are thinner than the starting ones and work on lower load lines in their respective B-H planes. A feasible drawing is analytically defined, which is robust against demagnetization at overload, showing that the saving of magnet quantity depends on the maximum current overload and can be significant. The theoretical formulation is validated with finite-element analysis and experiments on a prototype machin

Design of Ferrite Assisted Synchronous Reluctance machines robust towards demagnetization

The design of ferrite-assisted synchronous reluctance machines is investigated, with particular attention to the pivotal aspect of avoiding irreversible de-magnetization. Geometric rules for obtaining a robust design are proposed and described analytically. The safe operating area is quantified in terms of the corresponding maximum electrical loading. Such demagnetization limit shows to be depending on the operating temperature and the machine size. Furthermore, the comparison between the continuous load and de-magnetization conditions shows that low and medium size machines can be stiffer against demagnetization, with respect to larger machines, and have room for transient overload. The analysis is validated by finite-elements and a design example is given, namely a twelve poles direct-drive machine, rated 910 Nm, 200 rpm

Ferrite Assisted Synchronous Reluctance Machines: a General Approach

A general approach to the design of high performance ferrite-assisted synchronous reluctance motors is presented. Reference is made to a rectified rotor structure, with multiple flux barriers, designed to optimize the performance and the exploitation of the PM material. The key design issue of de-magnetization is analytically investigated, pointing out the maximum allowed current loading, depending on temperature and machine dimensions. Such current limit is then compared with the one imposed by the thermal constraint. The analysis shows that low and medium size machines tend to be robust against demagnetization, while larger machines are more at risk. The theoretical analysis is confirmed by finite-elements via an example machine desig

Multipolar Ferrite Assisted Synchronous Reluctance machines: a general design approach

A closed-form per-unit formulation for the design of surface-mounted permanent-magnet motors having high numbers of poles is hereby proposed. The analytical expression of machine inductances is presented, covering distributed and concentrated winding configurations. This paper addresses how the slot/pole combination, the geometric variables, and the number of poles are related to the average torque, the Joule loss, and the power factor. The performance of distributed and concentrated winding machines is analytically compared, in normalized quantities. Last, the design approach is tested on four design examples, including all winding types, and is validated by finite-element analysis