Harmonic reduction methods for electrical generation: a review

This paper provides a comprehensive literature review of techniques for harmonic related power quality improvement of electrical generation systems. An increasing interest in these aspects is due to the ever more stringent power quality requirements, deriving from new grid codes and compliancy standards, aimed at limiting waveform harmonic distortion at all points of the distribution network. Although a wealth of literature is available for such techniques, it has never been compiled into a handbook incorporating all the solutions aimed at both electrical machine and power systems engineers

Power quality improvement by pre-computed modulated field current for synchronous generators

Although power quality aspects of electrical machines have been extensively studied and investigated for a large number of years, room for improvement still exists in the field of classic, wound-field, synchronous generators. This paper proposes an innovative method of power quality improvement for single-phase synchronous generators in which the usual DC field current is replaced by a calculated current waveform. The optimised field current waveform is designed in such a way that harmonics created by the machine geometry and the winding configuration are significantly reduced

Simultaneous interplanetary scintillation and Heliospheric Imager observations of a coronal mass ejection

We describe simultaneous Interplanetary Scintillation (IPS) and STEREO Heliospheric Imager (HI) observations of a coronal mass ejection (CME) on 16 May 2007. Strong CME signatures were present throughout the IPS observation. The IPS raypath lay within the field-of-view of HI-1 on STEREO-A and comparison of the observations shows that the IPS measurements came from a region within a faint CME front observed by HI-1A. This front may represent the merging of two converging CMEs. Plane-of-sky velocity estimates based on time-height plots of the two converging CME structures were 325 kms?1 and 550 kms?1 for the leading and trailing fronts respectively. The plane-of-sky velocities determined from IPS ranged from 420 ± 10 kms?1 to 520 ± 20 kms?1. IPS results reveal the presence of micro-structure within the CME front which may represent interaction between the two separate CME events. This is the first time that it has been possible to interpret IPS observations of small-scale structure within an interplanetary CME in terms of the global structure of the event

A methodology to remove stator skew in small-medium size synchronous generators via innovative damper cage designs

This paper proposes and investigates an innovative methodology that can have a significant impact on the market potential of wound field, small-medium size synchronous generators. The technique proposed here is aimed at removing the need for the traditional stator skewing that is so commonly used in synchronous generators to achieve acceptable values of voltage total harmonic distortion. To do this, a non-standard damper cage configuration is proposed that comprises modulation of the damper bars’ positioning. An off-the-shelf, 400kVA generator is used as a benchmark machine. Its rotor is optimized and modified according to the proposed technique. The results of the final machine are then compared to the benchmark machine highlighting the excellent advantages that can be achieved through this technique. A full-scale prototype of the modified generator is then built to experimentally validate the concept. Finally, a detailed analysis on all the performance aspects of the prototype is done, to guarantee that the proposed technique has no negative impact whatsoever on the generator’s performance

The Continuing Search to Find a More Effective and Less Intimidating Way to Teach Research Methods in Higher Education

Existing literature examining the teaching of research methods highlights difficulties students face when developing research competencies. Studies of student-centered teaching approaches have found increased student performance and improved confidence in undertaking research projects. To develop a student-centered approach, it could be beneficial to teach students through active participation, with the development of their research agendas as the basis for progression. To develop this goal, the research methods module for graduate students at a UK business school was restructured into a two-week block utilizing a student-centered approach. The performance of the students was then compared to the performance of students who undertook the same course material presented in a traditional semester-long module and the results were then statistically analyzed. The results of this study provide new and interesting evidence of increased student achievement and understanding through the new format and provide new avenues for future research

Demonstration of surface electron rejection with interleaved germanium detectors for dark matter searches

The following article appeared in Applied Physics Letters 103.16 (2013): 164105 and may be found at http://scitation.aip.org/content/aip/journal/apl/100/26/10.1063/1.4729825The SuperCDMS experiment in the Soudan Underground Laboratory searches for dark matter with a 9-kg array of cryogenic germanium detectors. Symmetric sensors on opposite sides measure both charge and phonons from each particle interaction, providing excellent discrimination between electron and nuclear recoils, and between surface and interior events. Surface event rejection capabilities were tested with two 210 Pb sources producing ∼130 beta decays/hr. In ∼800 live hours, no events leaked into the 8–115 keV signal region, giving upper limit leakage fraction 1.7 × 10−5 at 90% C.L., corresponding to < 0.6 surface event background in the future 200-kg SuperCDMS SNOLAB experiment.This work is supported in part by the National Science Foundation (Grant Nos. AST-9978911, NSF-0847342, PHY-1102795,NSF-1151869, PHY-0542066, PHY-0503729, PHY-0503629, PHY-0503641, PHY-0504224, PHY-0705052,PHY-0801708, PHY-0801712, PHY-0802575, PHY-0847342, PHY-0855299, PHY-0855525, and PHY-1205898), by the Department of Energy (Contract Nos. DE-AC03-76SF00098, DE-FG02-92ER40701, DE-FG02-94ER40823,DE-FG03-90ER40569, DE-FG03-91ER40618, and DESC0004022),by NSERC Canada (Grant Nos. SAPIN 341314 and SAPPJ 386399), and by MULTIDARK CSD2009-00064 and FPA2012-34694. Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359, while SLAC is operated under Contract No. DE-AC02-76SF00515 with the United States Department of Energy

Exciterless solutions for medium-power wound-field synchronous generators

Exciterless solutions offer many benefits to the wound-field synchronous machine designer, most prominent of which is the significant potential increase in power density. Yet, whilst many topologies have been proposed, they exist only for low power machines and little previous work has been done for higher power units. Instead, the AC exciter remains the system of choice despite its disadvantages. This work investigates the scalability of existing exciterless topologies to larger machines, within the confines of minimising manufacturing changes. Through this, two new excitation topologies are developed, one of which provides an exciterless solution without any change to the main generator magnetic design. A functional prototype has been developed and validated, providing a full proof-of-concept for this methodology. The exciterless topology demonstrated in this work, along with the modelling and optimisation methodology used, provides a template for machine designers to rapidly update existing generator designs; finally unlocking the benefits of exciterless

Exciterless solutions for medium-power wound-field synchronous generators

Exciterless solutions offer many benefits to the wound-field synchronous machine designer, most prominent of which is the significant potential increase in power density. Yet, whilst many topologies have been proposed, they exist only for low power machines and little previous work has been done for higher power units. Instead, the AC exciter remains the system of choice despite its disadvantages. This work investigates the scalability of existing exciterless topologies to larger machines, within the confines of minimising manufacturing changes. Through this, two new excitation topologies are developed, one of which provides an exciterless solution without any change to the main generator magnetic design. A functional prototype has been developed and validated, providing a full proof-of-concept for this methodology. The exciterless topology demonstrated in this work, along with the modelling and optimisation methodology used, provides a template for machine designers to rapidly update existing generator designs; finally unlocking the benefits of exciterless