Insulation Design of Low Voltage Electrical Motors Fed by PWM Inverters
L. Lusuardi, A. Cavallini, M. Gómez de la Calle, J. M. Martínez-Tarifa, and G. Robles — Xplore Link
Parameters Influencing the Dielectric Loss of New Winding Insulation of Electric Machines
Xiaolin Chen — Xplore Link
Assessing the Proposed Test Sample by IEC/TS 60034-18-42 and Introducing a New Test Sample to Evaluate the Lifetime of the Turn Insulation
Iris Power- Qualitrol
Changes Sweeping the Field of Rotating Machine Insulation
This issue is focused on rotating machine electrical insulation. Thus I thought it would be appropriate to review the changes that I feel are occurring in the conventional rotating machine business, and the possible impact on electrical insulation developments. I will review the changes caused by a reduced reliance on large central generating stations, and the effect of new motor markets and motor controls.
In the past, electricity generation was mainly done in relatively large centralized generating stations using coal, oil, nuclear energy as a fuel to spin large turbine generators. In most utilities, the generators were often rated from 100 MVA to 1500 MVA, at a voltage of 11-25 kV. Generators rated above a few hundred megawatts were often cooled using direct water cooling and used high pressure hydrogen gas in the airgap. Electricity was also generated in hydro generating plants where the rotors were spun by falling water. Although mini-hydros are common, the main generating hydro plants tended to use generators rated between 10-1000 MVA, and 11 and 20 kV. That is, in the past, the main generating stations used relatively few large machines to create most of the electricity in the world. Thus, this focus on larger generators drove most insulation developments between 1950 and 2000.
Of course, things have changed in the past decade or so. In many countries, it is now harder to get the public to accept large centralized generating stations either because of environmental concerns, or the desire not to have such plants near where they live. Most governments are mandating the more efficient use of electricity through more cost-effective motors, time-of-use metering, better building thermal insulation and, of course, more efficient lighting. Where demand for electricity cannot be reduced by better utilization of the existing electrical plant, the increased demand (and replacement of the older conventional generating stations) is increasingly being met by wind turbines and photovoltaics. In contrast to conventional generation, each wind turbine tends to generate only 1-3 MW of power, compared to the much larger generators in conventional stations. In addition, most wind turbines tend to operate at a relatively low voltage (<1000 V), compared to 11-25 kV in conventional generators.
The significantly lower ratings of wind turbine generators mean the insulation system is very different from that in conventional machines. In fact, the insulation system is closer to that of low-voltage motors. The main ground insulation in the stator windings is often film insulation on the magnet wire with one or two layers of tape (with or without mica) and a slot liner. The low operating voltage of most stator windings in wind turbines means the partial discharge (PD) suppression coatings are usually not present. The rotor winding insulation in the doubly-fed induction generators that are common in wind turbines (where present – since a large number of wind turbines use permanent magnets) is very similar to the stator winding insulation, with similar voltage ratings. Of course the dramatic difference in ratings means the focus on insulation development is now on low voltage applications, and especially increasing PD resistance and reducing the thermal conductivity of the insulation system.
On the electricity use side, motors seem to be getting bigger and bigger, driven in part by the need to compress natural gas to liquid natural gas (LNG) for transport by ship. Conventional motors, as opposed to pump storage motor/generators, are now approaching 100 MW. The other trend is the ever-increasing application of variable frequency drives (VFDs) where electronic inverters provide the AC voltage of desired frequency so that motor speed and energy consumption can be controlled. Although such inverters have been around for many decades, since the early 1990s the development of better transistor switches and inverter topologies has enabled improved drive efficiency, reduced size and lower costs. Therefore, VFDs are now being rapidly adopted. Initially, the newer voltage-source, pulse-width modulation (VS-PWM) drives using insulated gate transistors were employed on low voltage motors (<1000 V). But now, such drive technology is used on the largest of motors. Some estimate that 50% of all new industrial motors will be supplied by invertors soon (if not already).
The principle feature of this new technology is that it produces voltage impulses with front rise times of less than 100 ns. These voltage impulses may generate partial discharge even in low voltage motors, and accelerate the aging of the PD suppression coatings in the higher voltage motors. The development of higher voltage transistors (which means the inverter will have fewer levels and be simpler to construct) and the introduction of silicon carbide switches, which can turn on in only a few tens of ns, thus improving the drive efficiency, will further increase the stress on the insulation systems. In the past 20 years there has been a flurry of conference and journal papers on the effects of voltage impulses on rotating machine insulation systems. The higher voltages and shorter switching times will see this effort continue.
Another aspect that is changing is the greater use of motors in aircraft and automobiles. The introduction of hybrid vehicles and now electric vehicles will drive a huge increase in the demand for motors in the 50 kW or so range, together with their VFDs. This application is challenging since the manufacturers want the motors to be as small and lightweight as possible, while lasting for at least 10 years in a contaminated, high vibration environment. These motors are also low voltage (about 400 V), so large currents and high temperatures are involved. These factors require considerable innovation in creating cost-effective insulation system designs.
Thus, electrical insulation innovation is still in high demand, both for materials and insulation system design, in spite of the rapid consolidation of the material supply companies and machine OEMs in recent years. But the focus of the innovation that is needed has changed from developing materials and systems to work at every high voltage and power level to more cost-effective, low voltage materials and designs.
From The Editors
From the Editors’ Desk May-June 2019
Late last year the Editors, together with Jane Hegeler, DEIS webmaster, prepared and distributed a member survey through the website and DEIS social media accounts. 244 survey responses were received. While there were many questions related to general membership activity, the purpose of the survey was to measure the interest around multiple proposed changes for the Electrical Insulation Magazine as well as its distribution format. Some of the responses follow. The majority of respondents have used materials from an EIM issue in a publication citing or as a teaching resource; we’re happy to hear that this publication continues to be a useful resource in our readers’ professional lives. As well, the vast majority of respondents answered positively to having a digital version of the magazine on the DEIS website; in response, the Editors have already taken action by making magazine content available under the “Publications” tab of the DEIS website. Among the changes proposed by the Publications committee to the Electrical Insulation Magazine, “Centering each issue on a specific topic” and “News from the around the world” were the most popular. As a result, recent issues have covered cable insulation, outdoor insulation, and transformer insulation. This issue is dedicated to machine insulation and future issues will be on GIS insulation and once again cables and transformers. We are fortunate to have Prof. Yoshimichi Ohki continue to send us interesting articles of activity in Japan. We welcome contributions from other parts of the world! Thank you to those who took the time to take the survey and provide us with feedback.
A word on DEIS Technical Committees of which there are ten. As Brian Stewart told us in his recent Editorial, “our Technical Committees embrace engineering technologies and look to understand better and apply these technologies for the benefit and future of our Society and the engineering community at large”. In the past two issues of the Electrical Insulation Magazine, we published reports from Giovanni Mazzanti on HVDC Cables Systems and James Pilgrim on Smart Grids. Throughout the remainder of the year, we will continue to bring these informative reports to our readers. In this issue, Hugh Zhu describes the recent activities of the TC on Aging Factors.
We recently also introduced a column for young researchers, students and engineers in our community to share their experiences and discuss matters related to their professional development. Contributors to this column have been Russell Frost, Valeria Pevtsov and Elizabeth Foley. Now Fabrizio Negri, a young researcher, shares interesting thoughts with us of his transition from a university laboratory environment into the challenges of research in industry.
Lastly, this issue brings back a past column on Industry News. Manitoba Hydro presents information about its High Voltage Test Facility and qualification testing for rotating machine winding insulation. The Editors look forward to receiving other contributions for future publication in the magazine.
This present issue of the magazine brings a series of articles dedicated to insulation systems of electrical machines.
The first article entitled “Insulation Design of Low Voltage Electrical Motors Fed by PWM Inverters” and is jointly authored by Luca Lusuardi and Andrea Cavallini from the University of Bologna, Italy, together with Manuel Gómez de la Calle, Juan Manuel Martínez-Tarifa and Guillermo Robles from the University Carlos III of Madrid, Spain.This paper discusses an approach to design inverter-fed low voltage motors that are inherently partial discharge-free in the turn/turn insulation, which remains the weakest point of the whole system. The worst case is considered, that is, when the impregnating resin does not fill the slot entirely, leaving microscopic cavities between the wires where partial discharge activity can take place. Thus, the goal is to determine the minimum conductor insulation thickness that ensures that partial discharges will not be incepted during operation. A model based on the streamer inception criterion is proposed to determine the partial discharge inception voltage and verify whether this is above or below the maximum stress imposed by the power converter supplying the motor. The model parameters are derived from experimental data and are validated by showing its capability to extrapolate partial discharge inception voltage values at elevated temperatures and low pressures. The model is also tested for wires having different diameters, insulation thicknesses and permittivity. The results show the sensitivity to various magnet wire parameters. Partial discharge inception voltage charts are eventually derived for the wire geometries established in the IEC Standard 60317-13, which may be used to reconsider recognised in it grade definitions for ensuring that most motors will be inherently free of partial discharges during operation.
The second article in this issue is on “Parameters Influencing the Dielectric Loss of New Winding Insulation of Electric Machines” and is authored by Xiaolin Chen from Brush HMA B.V., the Netherlands. It reports on investigations performed on winding insulation produced by the so-called global vacuum pressure impregnation technique (VPI). After briefly recalling the physical background of dielectric loss of winding insulation, the influence of material constituencies are elucidated, including the cure degree of epoxy, different types of mica tapes and different stress-grading tapes. The presented results show that use of different mica tapes may result in varied resin content, which, however, does not bring any insulation quality issues as long as the tapes are fully impregnated and cured. Furthermore, the dielectric loss caused by presence of PDs is also studied through tests on sample coils in which different artificial defects are made, including insufficient impregnation (dry mica layers), joint issue, delamination in main insulation and contact problem between main insulation and the slot. While the insufficient impregnation leads to the highest dielectric loss, the joint issue does not demonstrate much impact on this parameter. Also delamination in the main insulation causes significant increase of dielectric loss, much larger than that of a normal coil.
The third article reports on “Assessing the Proposed Test Sample by IEC/TS 60034-18-42 and Introducing a New Test Sample to Evaluate the Lifetime of the Turn Insulation” and is jointly authored by Davoud Esmaeil Moghadam, Joachim Speck and Steffen Grossmann from the Technical University of Dresden and Jürgen Stahl from VEM Sachsenwerk GmbH, Dresden, Germany. Authors of the paper critically analyze the tests introduced by IEC/TS 60034-18-42 standard, which describes controlling means and procedures to assess and evaluate the quality and durability of turn insulation used in drive-fed induction motors. It is claimed that the revision of this standard, made in 2008, remained very general and missed specific descriptions on how to prepare reliable test samples, especially referring to the length and the thickness of the used copper strands. Furthermore, according to the authors, the 2017 revision of the standard increased the difficulties by adding to the complexity of the test sample and test setup. It is thus possible that tests performed with the same materials at two different laboratories may yield different results. Moreover, the standard test structure only models the straight part of coils and is not suitable for studying the effects of curved sections. The paper presents results of investigations on how the length and the thickness of the used copper strands influence partial discharge inception voltage (PDIV) of the standard test samples. For comparison, tests on a complete coil with separated strands in the overhang are reported, suggesting that the latter arrangement better represents turn insulation by considering all practical conditions without introducing a dependency on the test sample dimensions.
The fourth and last article of the issue is entitled “Causes of Cyclic Mechanical Aging and its Detection in Stator Winding Insulation Systems”. It is authored jointly by Alessandro Cimino and Frank Jenau from the Technical University of Dortmund together with Christian Staubach from the University of Applied Sciences, Hannover, Germany.It refers to the change introduced to electrical machine operating conditions due to the increased use of renewable energy sources, where machines initially designed for base load operation are nowadays frequently operated at peak load conditions. This situation brings up increased stresses in the form of mechanical and thermo-mechanical forces that often result in severe mechanical aging. The article presents investigations aiming at increasing the knowledge on the dominating aging mechanisms in such conditions and is based on results of practical experiences and research work performed during the last 5 years. Accelerated multi-factor aging tests with simultaneously acting electrical, thermal and mechanical stresses on generator stator bars were done in a specially designed test rig and allowed to derive the mechanical lifetime curve providing the correlation between the absolute mechanical stress or strain and the number of stress cycles. Possibilities to apply various diagnostic tools for mechanical deterioration assessment, as well as their limitations, are also discussed. These include the use of partial discharge and dissipation factor measurements, as well as measurements of insulation resistance for determination of polarization index. In addition to classical dielectric diagnostic methods, investigation of vibration characteristics by means ofmodal analysis is presented for evaluating the condition of mechanically aged stator bar probes. Other presented innovative diagnostic techniques include THz-scanning, computer tomography and dielectric response analysis.
News From Japan
Development of an Ultrahigh Speed Camera with Multichannel Imaging
It is sometimes necessary to observe phenomena that are changing very fast in conducting research in various fieldsfrom basic physics to industrial applications. On such occasions, we need an ultrahigh speed camera. A Japanese company, Nac Image Technology, Inc., Tokyo, which is engaged in the development of such cameras, has recently developed an ultrahigh speed camera that can take images at a speed of 109 frames per second.
Figure 1 lists a variety of high-speed phenomena and their associated scientific or industrial events with framing rate required for each phenomenon. In early days, in order to observe fast changing events, a mechanical streak camera, which used either a mirror rotating at a very high speed or a slit system moving similarly speedily, was necessary. Its time resolution was limited by the maximum rotating speed of the mirror or moving speed of the slit.
In contrast to this classical high-speed camera,optoelectronic types are relatively new. Until mid-1990’s, a combination of a photocathode that emits electrons when hit byphotons, an electron accelerator, and a fluorescent plate that converts an electronic image into a visible image, was used as shown in Figure 2. Such an ultrahigh-speed camera is called an image converter camera. Figure 3 shows a physical appearance of a typical image converter camera, Ultra Nac, made in 1990 by a British company, Imco, which was a 100% subsidiary of Nac ImagingTechnology.
Figure 4 shows a typical imaging result taken in 1991 by the camera shown in Figure 3. We can trace clearly temporal changes of a shock wave induced by an explosion of silver azide, as pointed by the arrows. The framing rate was 2 × 105 frames per second with an exposure time of 300 ns for Figure 4.
In the mid-1990’s, a digital framing camera came out on the market. The digital camera uses a combination of an array of charge-coupled devices (CCDs) and an image intensifier, which is called an intensified CCD (ICCD) system. The camera has multiple sets of ICCD systems and a beam splitter. The image taken by the camera was first split by the beam splitter, and then each separated image was intensified by an individual image intensifier and recorded on a CCD array. By this process, the same image would appear on all the CCDs. Here, if we change the time at which the shutter of each image intensifier is open, sequential time-dependent behavior of the image can be acquired. The first camera of this multichannel type that appeared on the market was Imacon 468, sold by Hadland Photonics in the United Kingdom. The Imacon 468 had eight channels with a CCD array with 576 (horizontal) times 385 (vertical) pixels, and its attainable maximum framing speed was 108 frames per second and its shortest exposure time was 10ns.
The above-mentioned multichannel camera has several drawbacks. First, since it needs multiple image intensifiers, it must be large in size and high in price. Secondly, if the light amplification is different among the intensifiers, the resultant time-resolved image would be affected. In this regard, Nac Image Technology developed an ultrahigh speed camera using only a single image intensifier. For pursuing and realizing this technology, the company designed a special segmental image intensifier. Figures 5 and 6 show a physical appearance and the inside configurations of this camera, Ultranac Neo,respectively.
The developed image intensifier has 12 segmented areas as shown in Figure 7, and each area can work as an individual image intensifier. The image that passed through the objective lens is divided into 15 subimages, all of which will then reach the segmented areas. Therefore, by changing the gate timing of each segmented area, we can have 12 time-sequential images. Further, in 2017, the Ultranac Tau shown in Figure 8, which is capable of recording up to 109 frames per second, was released from Nac Image Technology and it contributes to a variety of research fields.
In the field of electrical insulation, there are many phenomena, to which ultrafast observation is desirable. Figure 9 shows the progress of an electrical discharge in water and the resultant growth of a cavitation induced by the discharge. While the upper 12 images were taken at a speed of 108 frames per second with an exposure time of 5 ns, the lower 12 images were taken at a speed of 105 frames per second with an exposure time of 100 ns.
This article was completed with the help of Mr. Hiroyasu Sasaki of Nac Image Technology, Inc.
Switching from University to Industry
Since I was a young student, becoming a researcher has been my dream. With such an ambitious desire, you can easily imagine why I decided to pursue a PhD study immediately after graduation. Luckily, I had the opportunity to join the Technology Innovation Laboratory of the University of Bologna, led by Professors Andrea Cavallini and Davide Fabiani, both being well recognized in the world as high voltage insulation experts.
My research project concentrated on a fundamental study about the feasibility of the introduction of nanofluids as an alternative to traditional and “green” fluids. Despite that this field of study had not been aligned with the solid insulation expertise of the laboratory, the passion in the search for new opportunities shown by Andrea Cavallini during my master thesis work made me think about accepting this challenge.
The world of nanofluids, although quite recent, is practically boundless because of the huge number of possible additives and raw materials to be used as the starting point; it was exactly what I was looking for: creativity, theory, interdisciplinary interactions, practice and possible application to the real industrial world.
Even in the perfect life, there is a moment in which you think that you need more, and in my case the turning point was the 2014 ICHVE, held in Poznan, Poland. This was the first international conference in which I participated, and the first moment when I showed the results of my studies. I remember very well that it also was the first moment when my “pure” knowledge became “contaminated” by the way of thinking within industrial companies. The “non-university” researcher I met there was Kevin Rapp, senior chemist at Cargill and the principal developer of the Envirotemp FR3, one among the most known natural esters on the market for transformer application. I will never forget his responses during our conversation; I was very excited when explaining to him the results of my experience, looking for a collaboration, a combined project together, but I quickly realized that he was more interested in the applicability of my results rather than in deep understanding of the effects I presented. He seemed not really fascinated by the beauty of the faster charge decay properties in semiconductive-based aggregation, which could determine the long-term properties of the fluid.
Interestingly, this “strategic” view was shared by other company researchers I met during my PhD period and slowly, but inexorably, it became my point of interest too. I started to think more about the possible implications in the real world, rather than understanding completely the scientific topic; I progressively stopped thinking and proposing creative theories able to explain the experimental data and started solving easier problems, but with an immediate application, with the awareness that this could be of immediate help for the world where we are living.
In this context I was very happy when I was contacted by Mr. Dario Santinelli, Trench Italia Siemens Group, for a research job in the factory where he was working, in the north of Italy.
Today, I am responsible for the innovation research projects dealing with high voltage instrument transformers in Trench Italia; I don’t work on nanofluids anymore; because the world is not yet ready for them, and therefore I came one step back to traditional and green fuilds, being less interested in understanding everything and keeping each phenomenon under control and, at the same time, more prone to find innovative opportunities and improve the quality of our life.
I continue participating in the IEEE sponsored conferences, building networks and exchanging knowledge with colleagues I had the luck to meet and, I have to say, I am more rewarded than when I was within the academic world. This does not mean that the pure research attitude is wrong; I am grateful that universities exist and people like Cavallini and Fabiani spend their lives at attempting to deeply understand all phenomena studied by them.
I consider myself still young and unripe, but I can give the younger generations a very simple advice: look at a blank book; if you see inside only equations and graphs, you are destined to a university career, if otherwise you see equations, graphs and pictures you will have to move to a company!
T.U. Daim, T. Oliver, and R. Phaal
World Scientific Publishing Co.
5 Toh Tuck Link
27 Warren Street, Suite 401-402
Hackensack, NJ 07601
791p. $198 (Hardcover), 2018
A technology roadmap is a document which outlines the plan to reach short-term and long-term goals through the use of technologysolutions. This book on technology roadmapping is a comprehensive resource for developing technology roadmaps.
It is broken down into four parts. Part 1 introduces technology management frameworks. They provide an overall view of the technology roadmapping process with perspectives from industry, government, and international viewpoints. For example, technology roadmapping methodology used by the Bonneville Power administration, a utility company in the US, for managing their R&D programs is outlined.
Part 2 provides various roadmapping methods presented through applications, case studies, and other tools that complement roadmapping methods. Some examples include a technology development envelope approach for energy storage technologies for smart grid applications and forecasting emerging technologies using bibliometrics and patent analysis. Other tools discussed include technology assessment, technology forecasting, and technology intelligence analysis.
Part 3 presents proven frameworks for roadmapping used by various organizations. Some of the technology areas address the renewable energy sector, emerging technologies, Japanese industrials, and stock market strategies.
Part 4 addresses applications to show examples of using the methods described in the book. Two applications covered are a case study for the energy sector and a case study for electric vehicles.
This book would be of interest to managers and technology leaders who need to develop technology roadmaps. By providing commonly used methods and case studies, the reader will be able to quickly gain a good understanding of the most common and successful methods for developing technology roadmaps.
Bulk Metallic Glasses, 2ndEdition
C. Suryanarayana and A. Inoue
CRC Press, Taylor & Francis Group
6000 Broken Sound Parkway – NW, Suite 300
Boca Raton, FL 33487-2742
542p. $151.96 (Hardcover), 2018
According to Wikipedia, an amorphous metal (also known as metallic glass or glassy metal) is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most metals are crystalline in their solid state, which means they have a highly ordered arrangement of atoms. Amorphous metals are non-crystalline, and have a glass-like structure. But unlike common glasses, such as window glass, which are typically electrical insulators, amorphous metals have good electrical conductivity. There are several ways in which amorphous metals can be produced, including extremely rapid cooling, physical vapor deposition, solid-state reaction, ion irradiation, and mechanical alloying.
In the past, small batches of amorphous metals have been produced through a variety of quick cooling methods. For instance, amorphous metal ribbons have been produced by sputtering molten metal onto a spinning metal disk (melt spinning). The rapid cooling, on the order of millions of degrees Celsius a second, is too fast for crystals to form and the material is “locked” in a glassy state. More recently a number of alloys with critical cooling rates low enough to allow formation of amorphous structure in thick layers (over 1 millimeter) have been produced; these are known as bulk metallic glasses (BMG).
Currently the most important application is due to the special magnetic properties of some ferromagnetic metallic glasses. The low magnetization loss is used in high efficiency transformers (amorphous metal transformer) at line frequency and some higher frequency transformers. Amorphous steel is a very brittle material which makes it difficult to punch into motor laminations. Also electronic article surveillance (such as theft control passive ID tags) often uses metallic glasses because of these magnetic properties.
This book provides details on the most recent advances in glass forming, corrosion properties, and mechanical behavior of bulk metallic glasses and covers the latest applications.
The book begins by providing extensive technical coverage on the glass-forming ability of certain alloys and synthesis methods for metallic glasses. Some of the topics covered include the effects of alloying elements on metallic glass properties transformation temperatures and physical properties. With synthesis methods covering the principles of rapid solidification and methods for achieving high rates of solidification. Some methods described are the flux melting technique, melt spinning, and glass casting methods. This information is very useful for anyone attempting to produce metallic glass.
The book continues by describing material properties and characteristics involving crystallization, physical properties, corrosion, mechanical, and magnetic properties. The chapter on crystallization covers behavior such as the crystallization modes found in melt-spun ribbons, the differences between melt-spun ribbons and bulk metallic glasses, and the effects, thermal stability, annealing effects, and the effects of pressure, magnetic field, ion irradiation on the metallic glass properties.
The chapter on physical properties covers density, thermal expansion, diffusion, electrical resistivity, specific heat, and viscosity of metallic glasses.
The chapter on corrosion behavior describes the corrosion of various types of metallic glasses which includes copper-based, iron-based, magnesium-based, and titanium-based metallic glasses.
The chapter on mechanical behavior describes the effects of fatigue and ductility response as a function of the composition of the metallic glass and the effects of the environment, microstructure, and temperature on metallic glass. The effects of the alloying elements and annealing on the magnetic properties are also described. Details on nanocrystalline materials and hard magnetic materials are also covered.
There is a wide variety of applications covered, some of which include motors, optical mirror devices, magnetic actuators, and medical applications.
For those who what to learn about metallic glasses and the synthesis and properties of metallic glasses and how to tailor their properties will find this book to be a very useful resource. It would also be useful for those looking to use metallic glasses in an application. The book provides the necessary background for understanding how metallic glasses can provide a unique type of material behavior that could enable a new application or improve efficiency.
Femtosecond Laser Shaping – From Laboratory to Industry
CRC Press, Taylor & Francis Group
6000 Broken Sound Parkway – NW, Suite 300
Boca Raton, FL 33487-2742
114p. $135.96 (Hardcover), 2018
Femtosecond lasers, once considered only a laboratory curiosity, are now a key component in the medical industry for certain eye surgeries. A femtosecond laser pulse (i.e. 10-15s) is an extremely short pulse width in which special light-matter interactions can occur, making this laser a very interesting area for researchers to explore.
This short book is written for those who want to learn about the femtosecond laser from an applications point-of-view. The author presents the material for a broad audience, leaving out technical rigor, but rather emphasizing on conveying the principles behind each description and a perspective on applications of a femtosecond laser.
The book begins by introducing femtosecond lasers with specific discussions on how the laser pulse is made and spectral phase. A discussion on light-matter interaction provides the reader with a qualitative understanding of what happens to the laser pulse when interacting with matter such as when the laser pulse passes through air or glass. Broadening of a laser pulse is described and the reasons for broadening are described. Pulse shaping methods, pulse characterization, and the generation of short pulses are also described. The remainder of the book describes applications. Some of these include biomedical imaging, explosives detection, surgery, and material processing. There are also discussions on potential new applications and scalability considerations for new laser designs.
This book provides an overview of femtosecond laser technology and is especially useful for gaining a quick grasp of the potential uses for femtosecond lasers. Sufficient references are given at the end of the book to allow the reader to delve into the technical details as desired. If you have any interest in femtosecond lasers or want to learn about applications for these lasers, this book will provide a quick read to get you inspired to further investigate this emerging technology.
MATLAB – A First Course for Engineers and Scientists
CRC Press, Taylor & Francis Group
6000 Broken Sound Parkway – NW, Suite 300
Boca Raton, FL 33487-2742
274p. $139.95 (Softcover), 2018
MATLAB (matrix laboratory) is a multi-paradigm numerical computing environment and proprietary programming language developed by MathWorks. MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages, including C, C++, C#, Java, Fortran and Python.
Although MATLAB is intended primarily for numerical computing, it can also be configured for symbolic computing abilities. Students, as well as working engineers, use MATLAB for solving complex problems numerically.
This book presets detailed explanations of the basic steps for learning MATLAB. To familiarize the reader with MATLAB, the book begins by introducing MATLAB programming methodologies, the MATLAB programing language and some example programs. The remainder of the book covers the fundamentals which include some example programs used to illustrate the techniques being presented. The fundamentals include basic MATLAB commands, trigonometric functions, the colon operator, plot commands, FOR loops, While loops, conditional operators, linear equations, functions, curve fitting, numerical integration, integration of ordinary differential equations (ODE’s), and boundary value problems of ODE’s.
This book would be useful for students or working engineers interested in quickly learning about the fundamentals of MATLAB. It provides a crash course on programming in MATLAB and is a convenient reference guide to refresh those who have not used MATLAB for some time.
Lessons from Nanoelectronics- A New Perspective on Transport – Part A: Basic Concepts
World Scientific Publishing Co.
5 Toh Tuck Link
27 Warren Street
Hackensack, NJ 07601
275p. $48 (Softcover), 2017
Nanoelectronics refer to the use of nanotechnology in electronic components. The term covers a diverse set of devices and materials, with the common characteristic that they are so small that inter-atomic interactions and quantum mechanical properties are studied extensively. Nanoelectronics are sometimes considered as disruptive technology because present candidates are significantly different from traditional transistors. This book is based on a set of two online courses recently offered on edX (online training courses www.edx.org) by the author.
The book can be separated into two parts. The first part covers the fundamentals of quantum mechanics and how it can be applied to microelectronics. The second part of the book shows how quantum mechanics can be applied for a better understanding of heat and current flow in general.
The first part begins with an overview of quantum effects in resistance. This topic is further developed to show why electrons flow in semiconductor materials. The Fermi function, an elastic resistor, ballistic and diffusive transport theories are introduced. These concepts are essential for understanding quantum mechanics. A simple model for the density of states is presented leading to a description of the nano-transistor properties. The first part then concludes with explanations for voltage drops along a semiconductor material. These explanations include the topics of the diffusion equation for ballistic transport, Boltzmann equation, quasi-Fermi levels, Hall effect, and p-n junction contacts. Again, this first part lays the groundwork for understanding quantum mechanics.
The second part expands on the principles described in the first part to explain heat and electricity in general. The concepts of thermoelectricity, phonon transport, the second law of thermodynamics, and equilibrium states are described. These concepts are used to help explain how heat is conducted in solids and how electricity can flow in metals and semiconductors.
The author has made this book accessible to many readers interested in learning about the fascinating world of nanotechnology by limiting the necessary background for understanding the book. The most in-depth parts of the book use differential equations and linear algebra and while many advanced concepts are introduced, the mathematical derivations are left as references for more in-depth study if desired. The book takes a very complex subject and makes very clear explanations, with many illustrations, that will give the reader an opportunity to understand these, oftentimes, counterintuitive concepts. Understanding these concepts allows one to more fully appreciate the sophistication of many of today’s electronic devices.
Prognostics and Health Management of Electronics – Fundamentals, Machine Learning, and the Internet of Things
M.G. Precht and M. Kang, editors
John Wiley & Sons, Inc.
111 River Street
Hoboken, NJ 07030
799p. $160 (Hardcover), 2018
Opportunities are growing for implementation of health diagnostics and prognostics of electrical and electronic systems down to the component level. Monitoring the degradation of critical components in a system and being able to provide a signal that indicates impending failure of a system component is one of the key features of the internet of things (IoT). Plans for predictive maintenance and automated signaling, using the internet, “cloud”, etc., without user intervention, is envisioned for many applications. Prognostics and health management (PHM), or prediction of a system’s remaining useful life (RUL), is a multifaceted discipline that can increase the reliability of systems by avoiding unanticipated problems that lead to malfunction and possible safety issues. By estimating the progression of a fault given the current state of degradation, the load history, and the anticipated future operational and environmental conditions, PHM can predict when a component or system will no longer perform its intended function within the desired specification.
This book provides a fundamental understanding of PHM, the physics of failures, data-driven approaches, and in-situ sensor systems for health and usage monitoring that enables prognostics for electronic components, products, and systems. This updated book provides current methods that take advantage of the latest communication equipment and protocols, sensors, and methods to monitor and predict component life.
Topics cover a comprehensive range of the subject matter, giving the reader the most current applications and methods used for PHM. The book is organized into three major parts. The first part covers the fundamentals of PHM. Some of the key topics cover techniques that enable prognostics for electronic products and systems including sensor systems, the Physics-of-Failure (PoF) approach to PHM, machine learning fundamentals and various topics of machine learning, representing uncertainty, determining the return on investment (ROI) of PHM, and health and RUL of electronic circuits.
The second part describes various applications areas that demonstrate the implementation of PHM. Some of these include Li-ion batteries, LED’s, medical devices, subsea cables, connected vehicles, and airlines. Methods used to set up PHM for each of these technology areas is illustrated including algorithms, analyzing large volumes of data, and methods to promptly identify root causes of faults by systematically using signal processing methods, machine learning, and statistical analysis approaches. These methods set an example that may be applied to other applications.
The third part of the book covers a variety of associated topics. Some of these are software for PHM, internet of things (IoT), driven predictive maintenance methods, a review of patents for PHM, a roadmap for PHM highlighting possible future directions, an appendix containing a list of commercially available sensor systems for PHM, and an appendix listing journals and conferences relevant to PHM. An extensive list of full references is provided at the end of each chapter.
This is a great book for someone who wants to learn about PHM and predictive maintenance methods. It provides good background into the methods currently in use in many applications where unexpected failures cannot be tolerated (e.g. airplanes, medical, etc.). There are numerous other application areas which may not be as critical which are being investigated to apply these methods, however, there is still a lot more development needed to get cost, size and power requirements of sensors to a desirable pointbefore many of these methods can be applied in widespread applications.
Ferroelectric Materials for Energy Applications
H. Huang and J.F. Scott, Editors
Wiley-VCH Verlag GmbH & Co.
KGaA, Boschstr, 12
69469 Weinheim, Germany
383p. $205 (Hardcover), 2018
Ferroelectricmaterials are crystalline materials that exhibit spontaneous electrical polarizations that are switchable, and reversible, by an external electric field. Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are also pyroelectric, meaning they havethe ability to generate a temporary voltage when they are heated or cooled. This change in temperature modifies the positions of the atoms slightly within the crystal structure, such that the polarization of the material changes. Generally, as a material is polarized by an external electric field, the induced polarization is linearly proportional to the magnitude of the applied external electric field.
This book describes the fundamental of ferroelectric materials and how they can be used as energy harvesting devices. For the benefit of beginners in this technology, the book begins by introducing the fundamentals of ferroelectric materials. It continues with chapters focused on applications for piezoelectric energy generation, ferroelectric photovoltaics, pyroelectric energy harvesting, electrocaloric cooling, electric energy storage, and photo-catalysis. Calculations are used to show how to explain or even predict material properties for energy applications. The final chapter of the book provides future perspectives of ferroelectrics for energy applications.
Some of the fundamentals cover mechanical energy harvesting using piezoelectric materials, thermal energy harvesting, the pyroelectric effect, various tertiary effects, and solar energy harvesting.
There is also a large amount of material presented on a variety of different types of multilayer ceramic capacitors (MLCC) and ferroelectric polymeric materials for electrical energy storage. Some of the nano-filled composites and multilevel nanocomposites presented show some interesting properties.
The fundamentals of electrocaloric effects is explained in detail and includes measurement methods and descriptions of various materials that can be used to exploit the electrocaloric effect to create cooling plates for refrigerator applications.
This book would be of interest to researchers working on ferroelectric materials and energy harvesting devices where experienced researchers can use it as a useful resource book and an update on the latest technology, while beginners can quickly learn about ferroelectric materials for energy harvesting applications.
Implementation of a Quality Management System for Laboratory Testing of Rotating Machine Winding Insulation
Laboratory testing plays an important role in the quality assurance of rotating machine winding insulation. Utilities employ third-party laboratories to qualify suppliers and assess their quality control through production. Because rotating machine windings are manufactured in factories from around the world, differences in industry standards and testing practices can exist regionally. Laboratory testing offers increased assurance that the qualification tests are performed in accordance with utility technical specifications and industry standards.
In 2011 Manitoba Hydro completed construction of a new high voltage test facility (HVTF) housing two test laboratories; the Bill McDermid High Voltage Test Hall, for testing 500 kV transmission class apparatus, and an Insulating Materials Test Lab for performing diagnostic tests on electrical insulation systems and insulating materials. The primary focus for work performed in the Insulating Materials Test Lab, is qualification tests on rotating machine winding insulation. Manitoba Hydro performs qualification tests on their own equipment, as well as for other utilities and equipment suppliers.
To provide quality testing services, Manitoba Hydro developed a quality management system (QMS) for work performed in its laboratories. The QMS is comprised of a set of operating procedures and technical work instructions that laboratory staff are required to follow. The system establishes protocols to ensure that staff have the necessary training and qualifications, that appropriate test methods are being used, that test equipment is functioning properly with the required degree of accuracy, and that customer needs are met.
The QMS in Manitoba Hydro’s HVTF has been operating functionally compliant to the ISO 17025 standard since 2016. Presently, Manitoba Hydro’s HVTF is in the application stage for an ISO 17025 accreditation in accordance with international standards IEEE 1310, IEEE 1043, and IEEE 1553. In this article, various components of the Manitoba Hydro HVTF QMS are presented at a high-level. The implementation of these components relating specifically to qualification tests for rotating machine winding insulation is discussed.
Staff and Qualifications
The laboratory team, comprised of specially trained engineers and test technicians is responsible for maintaining the QMS and performing tests in accordance with its various procedures and policies.
Under the QMS, test engineers are responsible for technical management, oversight of laboratory tests, data analysis, reporting, and preparing test plans to which test technicians adhere. Engineers also occupy various management roles which oversee the laboratory test program, including a Quality Engineer who is responsible for the development and execution of the QMS.
Laboratory test technicians must satisfy minimum requirements before becoming certified test technicians. These minimum requirements typically include a two-year college diploma in power electrical trades along with two years of specific on-the-job training. Subsequent to this training, technicians are required to undergo a proficiency exam and qualification process before being authorized to perform tests independently. Proficiency is evaluated based on test procedures defined in Technical Work Instructions, which have been prepared by Test Engineers and approved by Management and the Quality Engineer. Under observation of a qualified Test Technician or Test Engineer, Technicians must successfully perform work in accordance with a Technical Work Instruction to obtain qualification for a specific test.
Development of Testing Methods and Practices
Many of the test methods and practices for qualification tests on rotating machine bars and coils pre-date the construction of the Manitoba Hydro’s HVTF and development of its QMS. Manitoba Hydro Test Technicians have been performing winding insulation qualification tests for over 30 years. Many of these test methods were developed under the guidance of Bill McDermid, former Director of the Manitoba Hydro HVTF, and notably, IEEE Fellow for contributions to the development of rotating machine insulation testing.
As mentioned in the previous section, the laboratory test procedures are provided by Technical Work Instruction documents. These documents undergo a rigorous review and validation process before they are approved for use in testing. This validation process is continuous, and the test methods are audited at least once every 3 years.
One of the ways to validate a test method is by having two or more Test Technicians follow the same procedure and perform duplicate measurements on the same bar or coil specimen. The purpose of duplicate measurements is to determine if the procedure yields consistent test results. For example, when a capacitance and dissipation factor measurement is performed on a bar or coil, there is potential for some variability in the test setup and measurement. If two technicians apply inconsistent amounts of clamping pressure in the dummy slot, or they vary their placement of guard electrodes, then this might cause differences in their respective capacitance and dissipation factor measurements. The Technical Work Instructions must therefore be descriptive enough such that these measurements are executed correctly and consistently. In Manitoba Hydro’s QMS method, validation is a continual process and each Technical Work Instruction is subject to method audits at least once every two years.
Equipment Maintenance and Calibration
Equipment maintenance and calibrations are performed on regular scheduled intervals. In some cases, maintenance and calibrations are performed at intervals prescribed by equipment manuals or in industry standards. In other instances, intervals are based on best practices from laboratory experience. For example, in Manitoba Hydro’s Insulation Materials Test Lab, high voltage measuring dividers are maintained in accordance with recommendations from IEC 60060-2. Voltage divider accuracy is verified in annual performance checks, and the divider scale factor recalculated every five years. Conversely, temperature measuring devices, such as thermocouples used for measuring bar and coil surface temperatures during thermal cycling, receive performance checks every six-months. The reason for more frequent checks on thermocouples is based on Manitoba Hydro’s experience showing that they can drift out-of-tolerance more quickly as they begin to fail.
Drift in thermocouple accuracy is monitored by trending temperature measurement errors from performance checks over time. Statistical analysis of the performance check data is also applied so that any sensor displaying measurement errors more than two standard deviations out from the lot are monitored closely and may receive performance checks on a more frequent interval. These additional checks are done pre-emptively (for fear of drift) regardless of whether the sensor remains within the tolerance required for thermal cycling of +/- 2⁰C.
The statistical data acquired from performance checks are also used to estimate measurement error and uncertainty in rotating machine winding qualification tests. Test engineers maintain up-to-date estimates of the measurement error and uncertainty for voltage and temperature parameters.
Customer Service and Support
One of the most important components of a QMS is customer service and support. Laboratory staff work closely with customers through all stages from initial planning, to performing testing, to the final analysis and interpretation of test results. Laboratory staff have worked closely with customers to develop rotating machine winding insulation tests that are non-routine in nature, such as partial discharge and voltage endurance tests at elevated frequency, or capacitance and dissipation factor tests at elevated temperatures.
The HVTF QMS has well-defined protocols for handling customer complaints and non-conformances. These issues are entered and tracked electronically. Corrective actions are assigned to members of the laboratory team, and monitored by the Quality Engineer. Customers are informed of the impact or consequence of a non-conformance, along with corrective actions which have been applied. The Manager, Quality Engineer and Test Engineers review complaints, non-conformances, and corrective actions monthly to ensure services are continuously being improved. Customers are surveyed after the completion of a job and the team reviews the results annually.
For information on how the high voltage test facility can help meet your testing needs, email [email protected]or visit mhi.ca.
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