[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

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 Cycle.

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Comparison of Induction and PM Synchronous Motor Drives for EV Application Including Design Examples

Electric drive systems, which include electric machines and power electronics, are a key enabling technology for advanced vehicle propulsion systems that reduce the petroleum dependence of the ground transportation sector. To have significant effect, electric drive technologies must be economical in terms of cost, weight, and size while meeting performance and reliability expectations. This paper will provide details of the design, analysis, and testing of two permanent magnet (PM) machines that were developed to meet the FreedomCar 2020 specifications. The first machine is an interior PM (IPM) machine and the second machine is a surface PM (SPM) machine. Both machines are equipped with fractional-slot concentrated windings (FSCW). The goal of this paper is to provide a quantitative assessment of how achievable this set of specifications is, as well as a comparison with the state of the art. This paper will also quantitatively highlight the tradeoffs between IPM and SPM FSCW machines especially in the context of traction applications.

Comparison of Interior and Surface PM Machines Equipped With Fractional-Slot Concentrated Windings for Hybrid Traction Applications

Electric drive systems, which include electric machines and power electronics, are a key enabling technology for advanced vehicle propulsion systems that reduce the petroleum dependence of the ground transportation sector. To have significant effect, electric drive technologies must be economical in terms of cost, weight, and size while meeting performance and reliability expectations. This paper will provide details of the design, analysis, and testing of an advanced interior permanent magnet (PM) machine that was developed to meet the FreedomCAR 2020 specifications. The 12-slot/10-pole machine has segmented stator structure equipped with fractional-slot nonoverlapping concentrated windings. The rotor has a novel spoke structure/assembly. Several prototypes with different thermal management schemes have been built and tested. This paper will cover the test results for all these prototypes and highlight the tradeoffs between the various schemes. Due to the high machine frequency (~1.2 kHz at the top speed), detailed analysis of various loss components and ways to reduce them will be presented. In addition, due to the high coolant inlet temperature and the fact that the machine is designed to continuously operate at 180 °C, detailed PM demagnetization analysis will be presented. The key novelty in this paper is the advanced rotor structure and the thermal management schemes.

Advanced High-Power-Density Interior Permanent Magnet Motor for Traction Applications

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.

Electric Vehicle Traction Based on Synchronous Reluctance Motors

Electrical drive systems, which include electrical machines and power electronics, are a key enabling technology for advanced vehicle propulsion systems that reduce the petroleum dependence of the ground transportation sector. To have significant effect, electric drive technologies must be economical in terms of cost, weight, and size while meeting performance and reliability expectations. Interior permanent magnet machines with fractional-slot concentrated windings have been shown to be good candidates for hybrid traction applications. One of the key challenges is the additional stator magnetomotive force sub- and superharmonic components that lead to higher losses in the rotor as well as saturation effects. This paper tries to address this issue by looking into the concept of stator shifting. The generalized concept of stator shifting in the context of the harmonic components that are targeted for cancellation is presented; the focus is on single-layer and double-layer windings that have stator space subharmonics. It is shown that the stator shifting can reduce the loss-producing harmonics on the rotor as well as help the flux weakening performance of the fractional-slot concentrated winding designs. The cancellation of the loss harmonics is introduced as a method in which a particular harmonic can be targeted as well as reduce the phase inductance of the machine allowing for more room in terms of the operating voltage at higher speed. The concept of stator shifting will be explained, and the effect of varying the shift angle on the various harmonic components and winding factors will be investigated. Various designs, arising out of single-layer and double winding layer 10-pole, 12-slot configuration (targeting the FreedomCAR specifications) with varied shift angles are evaluated. The comparison between these designs in terms of their power density, efficiency, and torque ripple is presented.

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Generalized Approach of Stator Shifting in Interior Permanent-Magnet Machines Equipped With Fractional-Slot Concentrated Windings

Electric drive systems, which include electric machines and power electronics, are a key enabling technology for advanced vehicle propulsion systems that reduce the petroleum dependence of the ground transportation sector. To have significant effect, electric drive technologies must be economical in terms of cost, weight, and size while meeting performance and reliability expectations. This paper will provide details of the design, analysis and testing of an advanced interior permanent magnet (IPM) machine that was developed to meet the FreedomCar 2020 specifications. The 12 slot/10 pole machine has segmented stator structure equipped with fractional-slot concentrated-windings (FSCW). The rotor has a novel spoke structure. Several prototypes with different thermal management schemes have been built and tested. The paper will cover the test results for all these prototypes and highlight the tradeoffs between the various schemes.

Advanced high power-density interior permanent magnet motor for traction applications

Interior PM machines equipped with fractional-slot concentrated-windings are good candidates for high-speed traction applications. This is mainly due to the higher power density and efficiency that can be achieved. The main challenge with this type of machines is the high rotor losses at high speeds/frequencies. This paper will thoroughly investigate the effect of number of winding layers on the performance of this type of machines. It will be shown that by going to higher number of layers, there can be significant improvement in efficiency especially at high speeds mainly due to the reduction of the winding factor/magnitude of the most dominant stator mmf subharmonic component. It will also be shown that there is significant improvement in torque density. Even though there is reduction in the winding factor of the stator synchronous torque-producing mmf component, this is more than offset by increase in machine saliency and reluctance torque. The paper will provide general guidelines regarding the optimum slot/pole/phase combinations based on torque density and efficiency. Sample designs of various slot/pole combinations are used to quantify the benefit of going to higher number of layers in terms of torque density, efficiency, and torque ripple.

Effect of Number of Layers on Performance of Fractional-Slot Concentrated-Windings Interior Permanent Magnet Machines

There has been growing interest in electrical machines that reduce or eliminate rare-earth material content. Traction applications are among the key applications where reducing cost and, hence, reduction of rare-earth materials are key requirements. This paper will assess the potential of different variants of flux-switching machines (FSMs) that either reduce or eliminate rare-earth materials in the context of traction applications. Two designs use different grades of dysprosium-free permanent magnets (PMs), and the third design is a wound-field variant that does not include PMs at all. A detailed analysis of all three designs in comparison to the required set of specifications will be presented. The key opportunities and challenges will be highlighted. The impact of the high pole-count/frequency of the FSMs will also be evaluated. Experimental results for one of the designs with dysprosium-free PMs will also be presented.

Kum-Kang Huh

Papers

Advanced High-Power-Density Interior Permanent Magnet Motor for Traction Applications

Generalized Approach of Stator Shifting in Interior Permanent-Magnet Machines Equipped With Fractional-Slot Concentrated Windings

Advanced high power-density interior permanent magnet motor for traction applications

Effect of Number of Layers on Performance of Fractional-Slot Concentrated-Windings Interior Permanent Magnet Machines

Reduced Rare-Earth Flux-Switching Machines for Traction Applications