John M. Kern

Effect of Number of Phases on Losses in Conducting Sleeves of Surface PM Machine Rotors Equipped With Fractional-Slot Concentrated Windings

High-speed machines with a solid rotor or a high- strength retaining sleeve could offer design and performance advantages. For a specific application, if the use of a high-strength nonmagnetic metallic retaining sleeve is more advantageous than a nonmetallic (e.g., carbon fiber) one, one needs to evaluate the eddy-current losses due to armature reaction space and time harmonics and/or tooth ripple, as they can be significant. This problem is aggravated furthermore in fractional-slot concentrated-winding machines due to their inherent sub- and super nonsynchronous MMF harmonic components. In this paper, the impact of the number of phases is quantified to help design a lower eddy loss rotor sleeve for a high-speed surface-mounted permanent-magnet rotor machine with fractional-slot concentrated armature winding, FSPCW-SPM. The goal of this paper is to provide a general method for laying out preferred FSPCW configurations. Also, a general method for screening and choosing the optimal slot/pole combinations is presented.

Internal Fault Detection and Isolation for Paralleled Voltage Source Converters

This paper presented a systematic analysis of the protection methods for paralleled VSCs system especially with common DC bus from four types of internal faults, including short or open circuit faults of single switch or diode. The potential damages of such faults relating to circulating current were first explained. After that internal faults detection and isolation schemes based on de-saturation and circulating currents were shown in detail. The study confirmed that if the system can be shut down for a short period, SCRs can be used to recovery the system from internal faults with one redundant VSC. Otherwise, the topology with isolated DC buses for each VSC or other fast DC current breakers should be used. Finally, experimental results using a 2+1 VSCs system validated the analysis and protection schemes.

Effect of Number of Phases on Losses in Conducting Sleeves of High Speed Surface PM Machine Rotors

High-speed machines with a solid rotor or a high strength retaining sleeve could offer design and performance advantages. For a specific application, if the use of a high- strength non-magnetic metallic retaining sleeve is more advantageous than a non-metallic (e.g. carbon fiber) one, one needs to evaluate the eddy current losses due to armature reaction space and time harmonics and/or tooth ripple, as they can be significant. This problem is aggravated furthermore in fractional-slot concentrated winding machines due to their inherent sub and super non-synchronous mmf harmonic components. In this paper, the impact of number of phases is quantified to help design a lower eddy loss rotor sleeve for a high speed surface mounted permanent magnet rotor machine with fractional-slot concentrated armature winding, FSPCW-SPM. The goal of this paper is to provide a general method for laying out preferred FSPCW configurations. Also a general method for screening and choosing the optimal slot/pole combinations is presented.