Rukmi Dutta

A Comparative Analysis of Two Test Methods of Measuring

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

d

In this paper, design of a new interior permanent magnet (IPM) machine with very wide constant power operation range is presented. It has been seen that segmentation of the pole magnets and presence of iron bridges between magnet segments provide an inherent flux-weakening capability to the IPM rotor. Consequently, a very wide flux-weakening range is achievable with standard distributed stator winding. The flux-weakening capability of the new rotor was compared to a conventional IPM rotor using the same stator. The paper also presents the design optimization process and experimental verification of performance characteristic of the proposed machine as a case study of a 42 V alternator operation in which the constant power speed range is from 600 to 6000 r/min

- and

This paper presents the design and the experimental verification of an 18-slot/14-pole fractional-slot concentrated winding interior permanent magnet machine. The prototype machine was optimized for wide constant power speed range (7:1) and very low cogging torque, two of the most important requirements for traction machines. Measured performance of the constructed prototype machine has confirmed the finite-element modeling results. Experience gained from this study has led to develop a set of design rules for the concentrated winding (CW)- interior permanent magnet (IPM) machine. Scaling up of the prototype design based on these rules is also discussed in this paper.

q

This paper investigates inductance characteristics of a novel 14 pole/18 slot, fractional-slot concentrated-winding (FSCW) IPM machine. The variations of the self and mutual inductances were calculated analytically and also obtained from the finite element model. These results were compared with experimentally measured values of the self and mutual inductances of the prototype machine. Study of the inductance characteristics reveals that both self and mutual inductances vary with rotor positions nonsinusoidally. Presence of harmonics in the magnetomotive force (MMF) is responsible for this nonsinusoidal variation of inductances. The conventional distributed winding machine does not have these harmonics. This paper analyses the contribution of these harmonics in the Ld and Lq parameters in a dq-model of the prototype FSCW machine constructed. The self and mutual inductances were represented by a Fourier series in the inductance matrix of the machine for dq-transformation. It was seen that the difference between d- and q-axis inductance is mainly contributed by the harmonic terms of the mutual inductance.

-Axes Inductances of Interior Permanent-Magnet Machine

Wind turbines with higher power ratings are desired to reduce construction and maintenance time and increase energy yield. However, the high capital expenditure (CAPEX) at the start of the project presents a hurdle for such technology especially for gearless permanent magnet synchronous generators (PMSGs). This paper addresses research questions associated with the method by which the energy per cost is calculated. It aims at presenting a more accurate cost calculation based on a combination of methods that takes into account lifetime operation of wind turbines. The proposed method is used to evaluate typical PMSGs designed and reported in this paper as well as others available in the technical literature. The new methods outcome is compared to conventional methods. It is shown that lifetime cost calculations came in favor of gearless PMSGs, which has high CAPEX. It is also shown that when lifetime cost is included in the design optimization, it produces machines that provide lifetime revenues significantly higher than the extra CAPEX required.

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

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 Experimental Verification of an 18-Slot/14-pole Fractional-Slot Concentrated Winding Interior Permanent Magnet Machine

This paper investigates the reduced cogging torque seen in a prototype Segmented Interior Permanent Magnet (SIPM) machine. The Interior Permanent Magnet (IPM) machine in which the rotor pole magnets are segmented to provide an improved flux-weakening capability are called in this paper as the Segmented IPM (SIPM) machine. It has been seen that the cogging torque of the segmented IPM machine is much lower than that of a conventional, non-segmented IPM machine of similar ratings and dimensions. The cogging torques of both the segmented IPM machine and the conventional IPM machine were first calculated using finite element analysis and the results were later verified by the experimental measurements. The same stator was used for both the machine during calculation and measurements. The paper attempts to analyse the reasons behind the reduced cogging torque seen in the prototype SIPM machine.

Winding Inductances of an Interior Permanent Magnet (IPM) Machine With Fractional Slot Concentrated Winding

The use of concentrated windings in the interior permanent magnet (IPM) machine reduces its axial length and increases high-speed performance by enhancing flux- weakening capability although at the expense of higher cogging torque, decrease in winding factor and saliency ratio. In order to take full advantage of the concentrated winding in the IPM machine, optimization is required to minimize cogging torque and to maximize winding factor and saliency ratio. This paper is part of a detail investigation in which authors will attempt to optimize the concentrated winding structure for a high performance IPM machine. The full review of the existing optimization technologies for the concentrated winding applied to the permanent magnet machine is the first step toward developing new methods for the IPM machine. The paper presents the study of the various optimization techniques of the concentrated winding and their suitability in context with the IPM machine.

Lifetime Cost Assessment of Permanent Magnet Synchronous Generators for MW Level Wind Turbines

An analytical modelling technique to calculate the generated magneto-motive force (MMF) and back-EMF of fractional slot concentrated wound (FSCW) permanent magnet synchronous machines (PMSMs) is reported. The generated MMF of a FSCW stator is analyzed and modelled using a Fourier series technique. General expressions of the harmonic winding factors for FCSW stators with different slot-pole combinations are then obtained. A general expression for the generated back-EMF of FSCW PMSMs is then derived. The obtained analytical results are validated through finite-element analysis (FEA) and experimental tests on a prototype FSCW PMSM. A comparison between the generated voltages of various FSCW stator topologies is also performed.

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

Concentrated non-overlapping windings (CNW) have recently gained popularity due to key attributes of reduced machine axial length and simplified manufacturing. These attributes make it relatively more suitable for traction applications where reduced size and cost plays a vital role. In traction applications, good field weakening performance is desired. In this paper, the field weakening performance of the SPM rotor is compared to two different IPM rotor designs. Magnet eddy current loss with sintered, segmented and bonded magnets in SPM and IPM machines are also compared. Finite element analysis with Flux2D is used for this comparison due to its ability to handle complex calculations with non-linear material properties and precise geometry variations.