T.J. Flack

University of Cambridge | Cam

The losses in the electrical power generation system of a conventional internal combustion engine (ICE) vehicle is investigated. The system consists of a six-phase Lundell alternator and a six-phase passive rectifier. The losses of the alternator are measured using a test rig that simulates the ICE operation. It is shown that the Press-fit PN diode...

The development of cryogenic technology and high temperature superconducting (HTS) materials has seen continued interest worldwide in the development of HTS machines since the late 1980s. In this paper, the authors present a conceptual design of a 2.5 MW class synchronous motor. The structure of the motor is specified and the motor performance is a...

High temperature superconducting (HTS) synchronous motors can offer significant weight and size reductions, as well as improved efficiency, over conventional copper-wound machines due to the higher current density of high temperature superconducting (HTS) materials. In order to optimise the design parameters and performance of such a machine, this...

In this paper, the authors investigate the electromagnetic properties of stacks of high temperature super-conductor (HTS) coated conductors with a particular focus on calculating the total transport AC loss. The cross-section of superconducting cables and coils is often modeled as a two-dimensional stack of coated conductors, and these stacks can b...

AC loss can be a significant problem for any applications that utilize or produce an AC current or magnetic field, such as an electric machine. The authors are currently investigating the electromagnetic properties of high temperature superconductors with a particular focus on the AC loss in coils made from YBCO superconductors. In this paper, a 2D...

Purpose The purpose of the paper is to provide a comparison of first‐ and second‐order two dimensional finite element models for evaluating the electromagnetic properties and calculating AC loss in high‐temperature superconductor (HTS) coated conductors. Design/methodology/approach The models are based on the two‐dimensional (2D) H formulation, wh...

The brushless doubly fed machine (BDFM) shows economic promise as a variable speed drive or generator. The optimization of the machine and model-based control strategies both rely on machine models, and the experimental verification of these models. To date, dynamic measurements of rotor quantities have not been possible. The authors present a syst...

This paper investigates the electromagnetic properties of high-temperature superconductors with a particular focus on the AC loss in coils made from YBCO superconductors. The numerical analysis and finite element modelling of the YBCO superconductors used in Cambridge's superconducting permanent magnet synchronous motor currently in development is...

This paper examines the static micromagnetic properties of several configurations of sub-micron permalloy circular dots. Brief details of the two-dimensional (2-D) finite-element model used for the simulations are presented. The model is then applied to a 2×2 array of dots, showing that there is a single ground state in which the four dots assume a...

Experimental results from a frame size 180 brushless doubly fed (induction) machine (BDFM) fitted with four rotor designs are presented. The machine is intended for use as a variable speed generator, or drive. A per phase equivalent circuit for the machine has been developed and a method of obtaining parameters for the circuit is described. Express...

This paper presents a time-stepping shaker modeling scheme. The new method improves the accuracy of analysis of armature-position-dependent inductances and force factors, analysis of axial variation of current density in copper plates (short-circuited turns), and analysis of cooling holes in the magnetic circuit. Linear movement modeling allows arm...

The BDFM shows economic promise as a variable speed drive or generator. One practical obstacle to commercial exploitation is the presence of operating speeds at which BDFM synchronous action cannot be maintained under open loop conditions. In [7] the authors proposed a control strategy using feedback linearization, requiring full state feedback. In...

The paper presents experimental results to assess the performance of a variety of rotors used in a Brushless Doubly Fed Machine (BDFM). In the experiments the torque-speed characteristics were measured on a BDFM fitted with four rotors with five different windings. The measurements were made of the machine excited with just one stator supply with t...

This paper is concerned with the application of permanent magnet synchronous motors to high accuracy, high speed linear positioning systems. A number of possible control strategies for this application are discussed. The state-space model in the d-q reference frame is developed for the motor, and the application of feedback linearisation to this pr...

The BDFM shows economic promise as a variable speed drive. One practical obstacle to commercial exploitation is the presence of operating speeds at which BDFM synchronous action cannot be maintained under open loop conditions. Two control strategies are proposed: feedback linearisation and control winding phase angle control which will enable BDFM...

This paper extends the air-gap element (AGE) to enable the modeling of flat air gaps. AGE is a macroelement originally proposed by Abdel-Razek et al. (IEEE Trans. Magn., vol. 17, pp. 3250-3252, 1981; ibid., vol. 18, pp. 655-659, 1982) for modeling annular air gaps in electrical machines. The paper presents the theory of the new macroelement and exp...

This paper demonstrates how a finite element model which exploits domain decomposition is applied to the analysis of three-phase induction motors. It is shown that a significant gain in CPU time results when compared with standard finite element analysis. Aspects of the application of the method which are particular to induction motors are consider...

In this paper a finite element method, which combines domain decomposition with a novel technique for solving nonlinear magnetostatic finite element problems is described. It is then shown how the method can be extended to, and optimised for, the solution of time-domain problems

This paper describes how the A-ψ formulation may be applied to determine the losses in the stator duct spacers of large AC motors. The model is described in terms of its geometry and boundary conditions. The novel aspects of the application of the formulation to this problem are explained. These include the modelling of fixed currents sources (the...

The effect of the load on the iron loss in induction machines is usually neglected. However, the component of loss associated with high frequency flux ripples caused by stator and rotor slotting and mmf harmonics varies significantly with load, and can account for a substantial portion of the total iron loss. This is confirmed by theoretical and ex...

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The authors outline a technique which enables two-dimensional finite-element analysis to be applied to skewed machines. It involves representing the continuous skewing in a series of discrete steps. Each step may be modeled in two dimensions. The model has been applied to a salient-pole synchronous generator and to a cage induction motor. It is sho...

A three-dimensional finite-element model is used to investigate the effect that radial ventilation ducts have on the equivalent-circuit parameters of cage motors. It is shown that ducts change rotor resistance at starting, and an approximate method is proposed to allow for this effect. Detailed flux calculations are also used to verify some of the...

This paper describes an investigation into the effect that employing closed rotor slot designs in squirrel cage induction motors has on the air-gap flux density waves, and hence on the radial pressure waves acting on the stator. The method of analysis is firstly described, followed by tables of results which illustrate the effect of progressively c...

The authors describe the application of a three-dimensional eddy current formulation to the problem of the calculation of the current density distribution in the bars of cage rotor induction machines with radially ducted rotors under steady-state conditions. The most suitable choice of formulation and its application to the ducted rotor problem are...