Paul Lefley

A novel prototype design for a transformer for high voltage, high frequency, high power use

A prototype transformer has been designed and built which is novel in its combination of high voltage (50 kV), high frequency (20 kHz) and high power (25 kVA) specifications. The design technique utilized a spreadsheet approach which facilitated an iterative design procedure. The transformer used a ferrite core, nylon insulated secondary bobbins and pressurized sulfur hexafluoride encapsulation. It was designed as part of a high-voltage switched-mode power supply for driving electrostatic precipitators. The transformer was field tested at a large coal-fired power station and was found to have an efficiency of better than 98%.

Design and control of the Brushless Doubly Fed Twin Induction Generator (BDFTIG)

The aim of this paper is to present indirect vector control (IVC) for grid operation of a Brushless Doubly Fed Twin Induction Generator (BDFTIG). The goal is to control the power flow into the grid with a variable speed prime mover such as a wind turbine.

Study of the performance characteristics of a surface permanent magnet motor at various magnetization patterns

Purpose In the present paper the influence of the magnetization patterns of rotor magnets on the performance characteristics of a surface permanent magnet (SPM) motor has been investigated. The purpose of this paper is to show how the electromagnetic and electromechanical characteristics of this type of motor can be significantly changed by applying various magnetization patterns of permanent magnets (PM) on the rotor surface. Design/methodology/approach First, a survey of possible and most frequently used magnetization patterns for PM motors is presented. The research is focussed on the comparison of performance characteristics and is developed at three levels. The study starts with investigation of a conventional SPM motor having segmented PM, and two magnetization patterns are considered: parallel and radial. As there was no significant difference in motor performance at parallel and radial magnetization, for further investigation only radial magnetization, being more conventional, was considered. In the second step, the counterparts of SPM with two Halbach array configurations, under the constraint of fixed magnet volume, are studied. Finally, detailed comparative analyses of SPM at radial, Halbach 1, and Halbach 2 magnetic patterns are presented. The advantages and drawbacks of the suggested magnetic configurations are then discussed. Findings The authors have shown how the magnetization pattern of rotor PM can have a substantial impact on the SPM motor performance characteristics. From the analysis of magnetic field properties at various types of magnetization, it is observed that both the shape and the rates of the characteristics, for radial magnetization and Halbach 2 configuration, exhibit similar features. This is because the Halbach 2 array cancels the magnetic flux above the PM – that is, it strengthens the magnetic field in the rotor, and enhances the coupling between the rotor and stator magnetic field. It is worth emphasizing that, because of less saturation of the magnetic core and lower iron loss at Halbach 1 and Halbach 2 magnetization, it is possible to increase the armature current and consequently increase the electromagnetic torque. This finding could be an interesting for further research. Originality/value The paper presents an original comparative analysis of the performance characteristics of a surface permanent motor at various magnetization patterns. The novelty of the paper is seen in the introduction of two Halbach magnetization arrays for PM and improvement of the performance characteristics of the analysed motor.

Analysis of the stator topology impact on cogging torque for surface permanent magnet motor

Purpose – The purpose of this paper is to investigate the impact of the stator core design for a surface permanent magnet motor (SPMM) on the cogging torque profile. The objective is to show how the cogging torque of this type of motor can be significantly reduced by implementing an original compound technique by skewing stator slots and inserting wedges in the slot openings. Design/methodology/approach – At the beginning generic model of a SPMM is studied. By using FEA, for this idealised assembly, characteristics of cogging and electromagnetic torque are simulated and determined for one period of their change. Afterwards, actual stator design of the original SPMM is described. It is thoroughly investigated and the torque characteristics are compared with the generic ones. While the static torque is slightly decreased, the peak cogging torque is almost doubled and the curve exhibits an uneven profile. The first method for cogging torque reduction is skewing the stator stack. The second technique is to in...

Synthesis and analysis of a high‐performance low‐cost permanent magnet brushless DC motor

Purpose – The paper presents design development of a novel high‐performance low‐cost 6/4 pole permanent magnet brushless DC (PMBLDC) motor. The objective is to show how the cogging torque of this new design is minimised by determining the optimum stator pole arc length and the best shoe thickness.Design/methodology/approach – At the beginning a step‐by‐step design synthesis of a reference 6/4 pole PMBLDC motor with concentrated 3‐phase windings and asymmetric stator pole arcs is presented. It is followed by a full performance analysis of the reference motor. The FEM for electromagnetic field computation is employed. The characteristics of the motor are calculated and analysed. By simple variation of the stator pole geometry, two‐stage design optimisation for cogging torque minimisation is performed, and an optimised motor model is proposed. The comparative analyses of the reference and optimised motor models show the advantages of the proposed novel design.Findings – The focus is to show the sensitivity o...

A novel approach to multi-objective efficiency optimisation for a distribution transformer based on the Taguchi method

In this paper a new approach to multi-objective design optimisation of a distribution transformer is proposed. It is based on a combined pattern search optimisation technique and the Taguchi methodology. The objective was to increase the transformer efficiency by reducing the total transformer loss, coupled with the aim to minimise the iron and copper mass, and hence to attain a new, more efficient, lower cost product. The transformer that was selected for this research work was an existing oil immersed three-phase, 50 kVA, 20/0.4 kV unit from the production line of the Rade Koncar factory in Skopje. The Taguchi method and the Design of Experiments (DoE) were employed to achieve the optimisation objective and to minimise the total mass of the active materials. A non-linear mathematical model of the transformer was developed and an objective function, presenting the efficiency, was derived. Pattern search optimisation technique for higher efficiency, lower loss, and lower overall mass was invoked; and the outcome was an optimal transformer design. The results, both analytical and numerical using 3D FEM, have been validated through measurements from a new prototype. They show very good agreement, and prove the new approach was effective and accurate.

Optimal design of a novel single phase PM BLDC motor using Genetic Algorithm

In the past few years Genetic Algorithms (GAs) have proved to be a very powerful and reliable optimisation tool. They have also been successfully applied in the design optimisation of many electromagnetic devices. Therefore, in this paper the optimal design performed on the single phase permanent magnet brushless DC motor (SPBLDCM) is done by using a Genetic Algorithm. The objective function of the optimisation search is selected to be the efficiency of the motor and the design process is defined as a maximisation problem. Based on the values of some specific motor parameters, a comparative analysis of the improved motor and the initial motor design is performed. As an addition to the comparative analysis, a Finite Element Method modeling and analysis of both models is also performed.

Investigation of optimal IGBT switching behaviours under advanced gate control

This paper investigates the advanced IGBT gate driving strategies which optimizes its switching behaviours and compares with the conventional driving method. The optimal IGBT performance not only relies on its advanced semiconductor design and fabrication techniques, but also the optimized local control and protection from intelligent gate drivers and global converter control strategy. An advanced and appropriate driving strategy can further improve the performance and reliability of the power electronics systems, and exerts the full potential of the power semiconductor device. A comparative study of typical active gate drive methods and the effects of varying gate driving parameters has been conducted and examined and their pros and cons have been discussed.

Optimal switching performance of IGBT using active gate drive for PWM converters

This paper investigates the IGBTs switching characteristics and its gate drive with state-of-the-art control strategies. During the switching transients, the turn-on and turn-off delay time, current/voltage overshoot, switching losses dissipated in IGBT and electromagnetic interference are all related to its driving circuit. Hence, an advanced and appropriate driving strategy can further improve the performance and reliability of the power electronics systems, and exerts the full potential of the power semiconductor device. A comparative study of typical active gate drive methods has been conducted and switch dynamics and stress factors are evaluated by analytical expressions and simulations. Their pros and cons have been discussed.

Specific power based optimal design of novel single phase PM BLDC motor using GA

In this paper a genetic algorithm based optimal design of a single-phase permanent magnet brushless DC motor (SPMBLDCM) is proposed. This approach employs a genetic algorithm (GA) technique as a search tool for the optimization process of the SPMBLDCM. The specific power of the motor is selected as an objective function. At the end of the optimisation a best solution is proposed based on the values of the optimisation parameters, as well as other important motor parameters. An overall comparison of the best optimal solution and the basic model of the motor is presented.