High-speed applications involve technical and economical advantages, because as direct drives they avoid the gear as an additional mechanical drive component Permanent magnet synchronous machines are attracting growing attention for high-speed drives. Surface mounted permanent magnet synchronous machines request a glass or carbon fibre bandage to fasten the magnets to the rotor surface at high speed. At rotors with "buried" magnets the rotor iron itself fixes the magnets. The paper presents simple calculation strategies and discusses their limits for the mechanical design of high-speed machines with either surface mounted or buried magnets. The results of the calculations are compared with FE-calculations.

Fixation of buried and surface-mounted magnets in high-speed permanent-magnet synchronous machines

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

This paper reviews many design issues and analysis techniques for the brushless permanent-magnet machine. It reviews the basic requirements for the use of both ac and dc machines and issues concerning the selection of pole number, winding layout, rotor topology, drive strategy, field weakening, and cooling. These are key issues in the design of a motor. Leading-edge design techniques are illustrated. This paper is aimed as a tutor for motor designers who may be unfamiliar with this particular type of machine.

A Review of the Design Issues and Techniques for Radial-Flux Brushless Surface and Internal Rare-Earth Permanent-Magnet Motors

The interior permanent-magnet (IPM) machine is used in many industrial drives. In order to analyze performance and to design efficient and fast controllers, accurate knowledge of machine parameters such as d- and q-axes inductances is essential. Although there are a number of methods available to calculate these inductances, none of them is considered standard. Accuracy levels of all these methods are also not consistent, and some of the measurement methods require complicated arrangements. Among these test methods, the ac standstill test and a newly developed test method that uses vector current control technique are ideal for a laboratory environment. In this paper, these two methods are compared by applying them to a prototype IPM machine. The paper analyzes the test results of the methods and their differences in detail with the help of finite-element analysis

A Comparative Analysis of Two Test Methods of Measuring $d$ - and $q$ -Axes Inductances of Interior Permanent-Magnet Machine

This paper evaluates the design of a new segmented interior permanent magnet (SIPM) machine with very wide constant power operation range. The machine uses segmentation of the rotor magnets with the help of iron bridges between magnet segments. This provides for an inherent flux-weakening capability to the interior permanent magnet (IPM) machine. A very wide flux-weakening range has been achieved by using a standard distributed stator winding only. The flux-weakening capability of the proposed SIPM motor was compared to a conventional IPM machine. The same stator was used in both machines for direct comparison. The paper also presents the design optimization process and experimental verification of the performance of the proposed machine as a case study of a 42 V alternator operation in which the speed range is from 600 to 6000 r/min.

Design and Analysis of an Interior Permanent Magnet (IPM) Machine With Very Wide Constant Power Operation Range

This paper discusses mechanical design considerations that are particular to conventionally (i.e., radially) laminated rotors of interior permanent-magnet synchronous machines. Focus is placed on applications where the radial forces due to high-speed operation are the major mechanically limiting design factor. Proper design of the lamination bridges, or ribs, at the rotor outer diameter is explained in terms of the both material considerations and electromagnetic performance impact. The tradeoff of complexity versus performance associated with using strengthening ribs in the magnet cavities is discussed. The sensitivity of the mechanical design limitations to the rotor-shaft mounting mechanism is also highlighted. These effects are then analyzed using finite-element analysis for a 150-N/spl middot/m/6-kW integrated starter/alternator designed for operation up to 6000 r/min with an annular rotor to accommodate a torque converter or clutch assembly. This example demonstrates that it is possible to significantly improve the rotor's structural integrity using the techniques described in this paper with only a very modest impact on the projected machine drive cost.

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Mechanical design considerations for conventionally laminated, high-speed, interior PM synchronous machine rotors

This paper presents the design and experimental verification of a 6 kW interior permanent magnet (IPM) synchronous machine intended for an automotive direct-drive starter/alternator application The machine was designed using a saturable lumped-parameter magnetic circuit model in combination with a Monte Carlo optimization process that minimized the machine-plus-converter cost An experimental IPM machine has been constructed based on the resulting design specifications Laboratory tests have confirmed the accuracy of the analytical models for predicting the q-axis inductance L/sub q/ (including saturation effects) and the torque production characteristics, but discrepancies between the predicted and measured d-axis inductance L/sub d/ were revealed The impact of these differences on machine performance is discussed, as well as potential adjustments in the IPM analytical model to improve the performance of future machines

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Design and experimental verification of a direct-drive interior PM synchronous machine using a saturable lumped-parameter model

This paper discusses mechanical design that are particular to conventionally (i.e., radially) laminated rotors of interior permanent-magnet synchronous machines. Focus is placed on applications where the radial forces due to high-speed operation are the major mechanically limiting design factor. Proper design of the lamination bridges, or ribs, at the rotor outer diameter is explained in terms of the both material considerations and electromagnetic performance impact. The tradeoff of complexity versus performance associated with using strengthening ribs in the magnet cavities is discussed. The sensitivity of the mechanical design limitations to the rotor-shaft mounting mechanism is also highlighted. These effects are then analyzed using finite element analysis for a 150 Nm/6 kW integrated starter/alternator designed for operation up to 6000 RPM with an annular rotor to accommodate a torque converter or clutch assembly. This example demonstrates that it is possible to significantly improve the rotor's structural integrity using the techniques described in this paper with only a very modest impact on the projected machine drive cost.

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T.A. Keim

Papers

Mechanical design considerations for conventionally laminated, high-speed, interior PM synchronous machine rotors

Design and experimental verification of a direct-drive interior PM synchronous machine using a saturable lumped-parameter model

Mechanical design considerations for conventionally-laminated, high-speed, interior PM synchronous machine rotors