Multiphysics software speeds the optimisation of electrical machines.

A powerful new version of the Opera electromagnetic and multiphysics design software has been launched by Cobham Technical Services. The new version 18 release of this renowned finite element analysis and simulation software incorporates numerous enhancements to boost functionality, speed and accuracy, while further improving ease of use.

Key new features in Opera v18 include a powerful analytic tool to help users quickly assess different winding configurations in rotating electrical machines. A new graphical analysis setup tool brings drag-and-drop editing simplicity to complex evaluation sequences involving multiphysics simulation. The modelling of materials with very small skin depths is also made much simpler by a new surface impedance boundary condition for transient electromagnetic analysis; the code for this software is also specifically structured to allow parallel processing to accelerate analysis.

The new tool for electrical machine design can shorten development times significantly, by allowing highly detailed investigation of possible winding options prior to finite element analysis and simulation of the most promising designs. Called the Winding Tool, it enables designers to assess the feasibility and efficiency of different coil winding configurations – and their impact on machine performance – very easily and quickly. The software includes a winding wizard which creates a report of all feasible windings for a user-specified range of slots and poles, backed by detailed winding characteristics for each slot-pole combination. It is available for both the two-dimensional and three-dimensional Opera design software packages.

In the case of an electric motor design for example, designers could initially use the Winding Tool to define parameters such as the number of phases, slots and poles. A feasibility indicator instantly shows whether the specified configuration can be realised with single layer windings, while ‘calculate’ and ‘load’ buttons enable individual sets of current or previously stored parameters to be analysed. As standard, the tool provides six different types of graphical output, each accessed easily by a tabbed selector. These comprise circular and linear representations of the optimal winding layout and a ‘star of slots’ representation of harmonic amplitude, together with graphs of winding factor and winding magnetomotive force (MMF) harmonics and a voltage phasor (Görges) diagram.

After verifying winding feasibility, designers would typically use the Winding Tool’s parameter input and graphical output facilities interactively, to investigate how potentially viable winding configurations could be improved or adapted to meet specific motor design objectives. For example, the effect of various winding skew angles on harmonics can be examined in detail as part of the design process - to minimise cogging torque, noise and vibration. The full set of results from each Winding Tool calculation is made available to other Opera facilities in the form of an Opera Object in the Python programming language.

The Opera-3d Modeller now has a graphical tool to simplify the preparation of data for analysis. It provides users with a very convenient means of controlling the sequence of analyses, using drag-and-drop editing to add or remove specific analysis stages to a list. Context sensitivity allows the tool to give instant visual feedback on the validity of requested changes, while the properties and parameters of analysis stages can be adjusted within the tool’s environment. Individual analysis stages can be saved out and used in other sequences to further speed the design process.

The new Analysis Setup tool simplifies advanced multiphysics simulation significantly, including transient cases. Users can now set up a complete chain of electromagnetic, thermal and stress analysis simulations for example, with no limit on complexity or sequence. Loops are allowed and the results from one simulation are passed automatically to the next. Shape deformation caused by forces acting on a model can be employed across different types of simulation; the deformed mesh from stress analysis can be nominated for use in subsequent electromagnetic or thermal analyses. In the case of coils, the software automatically accommodates any changes in current density values due to shape deformation, facilitating very accurate electromagnetic field analysis.

Another major feature in the latest release of Opera-3d is that the scope of the surface impedance boundary condition (SIBC) has been widened and is now available for use in transient electromagnetic analysis – including Demagnetization and Motional Analysis. This simplifies the modelling of materials with a very thin skin depth (compared to the size of the model) by replacing the volume elements in a conducting region with surface elements. The variation of fields and currents below the material’s surface is represented by a decaying waveform which models the skin depth.

One of the major applications for the new transient SIBC feature is electrical machines. For example, it could be used to improve the accuracy of eddy current and skin effect analysis in conducting parts – to help designers minimise hard-to-combat sources of losses in large rotating electrical machines such as multi-megawatt AC generators. Eddy currents induced in the surface of conductive components such as lamination clamps, securing bolts and metal cable ties can account for kilowatts of dissipative energy in such machines. Minimising eddy current losses demands accurate modelling of the rate at which these currents decay due to skin effect, and is a task that traditionally can take many weeks of work.

The transient SIBC software code is structured to allow users to take advantage of parallel processing to speed analysis and simulation; the Opera Manager enables users to specify the maximum number of threads per job. While finite element analysis might seem an obvious candidate for code parallelisation – to gain a speed advantage from the shared memory architecture of computers with multi-core processors – some areas benefit far more than others. Cobham therefore employs a progressive development policy, initially targeting software pinch points that will provide users with the largest performance gains. The transient SIBC is a prime candidate – parallel processing can help to shorten analysis times for complex models significantly, often from weeks to days.

Version 18 of Opera also consolidates or extends a number of features that were introduced in the previous version of this software. These include the ‘solve as 2d slice’ feature, which is now standard in the Opera-3d Machines Environment. It enables users to evaluate machine performance using a one element thick slice obtained from the full 3d model, with the appropriate boundary conditions applied automatically. Depending on model complexity this can dramatically reduce the number of elements that need to be solved – often by several orders of magnitude – resulting in much faster solution times. There is almost perfect correlation between results obtained from the 2d slice and the full 3d model, and the 2d slice can be converted to 3d to analyse end-effects.

The graphical user interfaces of Opera-2d and Opera-3d continue to make increasing use of tabbed menus to simplify operation and many are now backed by keyboard shortcuts. Enhanced context sensitivity means that drop-down menus are much shorter and mainly replaced by menu bar icons, allowing fast, single-click navigation and control. All high-level user interface functions can be displayed in English, French, Chinese and Japanese.

Cobham has also taken the opportunity to further extend Opera’s interoperability. Version 18 extends the optional links previously available to a wider variety of third-party computer-aided design packages. These now provide the ability to work with CATIA, NX, Pro-Engineer Creo and SolidWorks files. IGES, Parasolid, SAT and STEP files offer CAD-neutral geometry access.

Electromagnetic design pioneers celebrate 30 years of success!

Three of the earliest Vector Fields employees still work for Cobham Technical Services
(LtoR) Chris Biddlecombe, John Simkin and Chris Riley.

Coinciding with Cobham’s 80th anniversary celebrations, the developers of the renowned Opera electromagnetic simulation software are celebrating the 30th anniversary of the Vector Fields Software business unit. Initially focused on making the design of particle accelerator magnets practical, their software tools remain at the leading edge of electromagnetic design today. This success is in large part due to continuing development of the founders' pioneering ideas for numerical software - which made possible the first practical commercial solution for solving complex and three-dimensional electromagnetic simulations.

The first major users for Opera software were almost all at the major physics labs around the world. At these sites, Opera was used to prototype advanced superconducting and resistive magnets for high energy and particle physics research - equipment which was too large and costly to prototype and refine in the normal 'cut and try' way. This user base at the very forefront of global scientific knowledge still remains a major strand of the company's business. However, the functionality of Opera and the user-friendliness of the design tools, has evolved almost beyond recognition to offer solutions for a much broader range of design requirements.

Opera has a distinguished track record of technological firsts and pioneering advances in electromagnetic design. Although progress in computing and graphics technology have been of enormous importance and often appear to underpin advances in the field, the background work of Opera developers on fundamental mathematical techniques, on accurately modelling material properties, speeding design entry and analysis, and optimising designs, has resulted in orders of magnitude improvements in the speed and fidelity of the virtual prototyping process. Today, much of the company's research revolves around allowing the software to perform ever more complex multi-physics simulation of electromagnetic design problems - taking into account factors such as mechanical stress and temperature – and improving performance using parallel computing.

"When we started in business, speed of simulation was the most fundamental challenge we faced," says Chris Riley, who was the fifth employee to join the early start-up Vector Fields business. "Even though we now have orders of magnitude more computing power, execution speed is still a critical challenge - because the scale and complexity of design problems also continually expands. It doesn't matter if you're designing a multi-million dollar magnet system for steering particle beams, or a $20 electromechanical actuator - today's users want to squeeze the last fraction of a percent of perfection out of any idea. And that demands capabilities such as 3D modelling, finer resolution of finite element meshing, consideration of multi-physics effects and intelligent optimisation. The challenges keep on coming, and overcoming them to deliver software that can be used to perform optimal electromagnetic design is the driving force behind Opera today."

The technology behind Opera began life at Britain's Rutherford Appleton Laboratories (RAL) who cooperated with CERN in the 1970s to help break down a barrier as particle physics research moved towards higher energy accelerators - the need to reliably design superconducting magnets. After initial work on volume integral formulation software the team looked at solving Maxwell's equations using the more versatile finite element analysis technique. Chris Biddlecombe, now Opera Development Manager, created a program called PE2D (Poisson's Equation in Two Dimensions) using magnetic vector potential, which met with considerable success. However, making a direct transition to three-dimensional analysis would not have been viable with the computer resources available in the late 1970s. This led RAL scientists Bill Trowbridge and John Simkin - who went on to found Vector Fields in 1984 – to develop a new computational technique based on the use of scalar potentials. The commercial electromagnetic finite element 'solver' - named TOSCA for TOtal SCAlar - was a breakthrough and won its developers the Maxwell Premium Award from the UK's IEE. Its ideas still form the basis of much of the Opera suite of tools today.

The core electromagnetic simulation technology was in place. The focus of much of the early work for the fledgling Vector Fields business was the development of a graphical modelling and post-processing environment, and analysis functionality - to create a comprehensive suite of user-friendly tools for the virtual prototyping design process. This all came together by the late 1980s, and it was dubbed Opera. Vector Fields continued successfully developing more application specific tools and advanced analysis capabilities, often in collaboration with prestigious partners, from leading-edge industrials to educational leaders. Vector Fields now trades under the Cobham brand after joining the Cobham group in 2005, where it has continued to grow and maintain its place as one of the world leaders.

Today, thousands of users employ Opera for design and simulation tasks for applications such as electrical machines, transformers, X-ray tubes, ion beam sources, ship signature calculations and non-destructive test equipment. The company's recent annual European User Group Meeting saw presentations on applications as diverse as HEV traction motors to particle accelerators, magnetic gearing to aerospace components.

Recent advances include parallel-processing capability to match modern hardware, the first multi-language versions and enhancements to deliver true easy-to-use multi-physics models.

“In the ever-advancing world of virtual prototyping there is no such thing as resting on your laurels” says Kevin Ward, director of the Vector Fields Software business. “We have an exciting five-year plan ahead of us for Opera, launching into new applications, putting it in the hands of a new wave of engineers, and establishing the technology in emerging markets.”

Evaluating the effect of forces in electrical devices

Cobham Technical Services has extended the multiphysics capabilities of the well-known Opera-3D finite element software for electromagnetic design with a new solver that can be used to analyse natural vibration modes. The tool is expected to prove particularly useful for electrical machine developers, who can employ it to investigate and minimise forces that might cause oscillations close to the natural frequencies of the equipment and thereby avoid excessive vibration or collisions between rotating and stationary parts.

By capturing such mechanical vibration in conjunction with electromagnetic modelling, and thermal performance if required, the integrated 3D (three-dimensional) tool suite can greatly reduce the complexity and timescales of design projects.

One of the key benefits of this capability is a further reduction in the need to create physical prototypes to explore the behaviour of a proposed design concept. With the greater understanding of new designs that more thorough simulation brings, it can be possible to reduce the real-world prototyping phase to a few iterations. This can take months out of design cycles - along with the associated high costs.

"Finite element simulation is the most practical tool for exploring design concepts and validating device performance. Adoption from the outset of the design process can stimulate innovation and lead to designs which are right first time," says Jeremy Howard-Knight of Cobham Technical Services. "With engineering skills at a premium, design automation using computer modelling is an extremely effective investment that companies can make to ensure successful products and a continuing flow of design ideas."

The latest version of the software extends the fundamental performance advantage of Opera for many common design engineering applications. Mechanical stress and vibration is an important consideration in the design of coils and windings in transformers, motors, generators, actuators, large electro-magnets, and superconducting magnets. For example, the mechanical integrity of the stator end windings of a generator subject to a short-circuit condition, or the ability of a superconducting magnet's coils to withstand the mechanical forces generated during a quench, are both critical design requirements.

The new modal solver - known as STRESS/EV - finds a user-specified number of eigenvalues within a specified frequency range and calculates the eigenvectors of each mode. It works in conjunction with the static stress analysis capability of Opera which calculates the deformation, stresses and strains of a body which is subject to external and internal forces. The forces calculated from electromagnetic fields can be used as input to the stress analysis.

STRESS/EV accommodates isotropic, orthotropic and fully anisotropic materials, the properties of which can be specified as a constant or an expression. The program uses the Young's modulus, Poisson's ratio and shear modulus of the material, together with its elasticity matrix if it is fully anisotropic.

Opera, from Vector Fields Software, Cobham Technical Services, provides a complete design-simulate-analyze-optimise toolchain for electromagnetic applications. The software is renowned for its accuracy of simulation and speed of execution. It is a modular product that includes finite element solvers for static and time-varying electromagnetic fields, and application-specific solvers for rotating electrical machines, superconducting magnets, charged particle beam devices, and magnetisation/demagnetisation processes.

Power transformer design site demonstrates benefits of software automation

Provides detailed introduction to virtual design using finite element analysis

A new website to help engineers accelerate and improve the design of electrical power transformers and AC line reactors has been launched by Cobham Technical Services.

Optimise the performance of electrical power transformers & AC line reactors.

Designed to be a useful resource for engineers seeking to optimise the performance of power transformers or reactors the new website provides clear insight into the benefits of automating the design process using finite element modelling, simulation and analysis by means of an on-demand detailed technical audio visual presentation.

'Introduction to Transformer Design' demonstrates the virtual design process. It explores the Opera design software to illustrate how finite element analysis (FEA) techniques enable conceptual designs of power transformers and reactors to be created, analysed and optimised easily. By allowing users to prove designs before building physical prototypes, this approach reduces production costs and shortens time-to-market significantly - and provides a simple means of fine-tuning design ideas to meet specific goals such as higher efficiency or reduction of materials.

Opera electromagnetic design
software enables users
to model any type of
transformer geometry.

Subjects covered include the definition of model geometry, finite element shapes, mesh density and material type, as well as transformer or reactor configuration, containment and winding layout. Open-circuit, short-circuit, inrush current and mutual inductance tests are described in detail, together with results analysis options. The presentation also highlights how it's possible to extensively automate the design-analyse-optimise process.

The presentation includes benchmark results on an internationally agreed family of problems defined to test the accuracy of simulation software in modelling transformers. Structural and thermal analysis capabilities are also covered briefly, showing how the electromagnetic FEA tool can encompass every aspect of transformer design and qualification. For engineers wishing to gain a more in-depth appreciation of multiphysics simulation, the website provides a link to a further detailed presentation.

The website also provides a dynamic overview of the low-frequency electromagnetic design automation software package Opera, as well as a wealth of information about finite element application areas and capabilities. Cobham is also further populating the site with technical papers and application notes on transformer design and optimisation.

Demystifying use of FEA for motor and generator design

A new web-based technical presentation from Cobham Technical Services helps designers of electric motors and generators use finite element analysis (FEA) techniques to accelerate product development and improve design accuracy. The presentation will also be of interest to electromagnetic and electromechanical analysts, as well as engineers who are currently using analytical design packages for rotating machines. First shown live to a pre-registered audience as a webinar, the 47-minute audio/visual presentation is now available - in English and French - for on-demand playback via Cobham's dedicated motor design software website.

Titled 'Introduction to Rotating Electrical Machine Design using Opera', the presentation outlines how Cobham's low frequency electromagnetic simulation software enables designers to improve the performance of motors and generators to meet specific economic, efficiency and operating environment targets. Making extensive use of graphics, it covers all key areas of FEA and is ideal for people who are new to the subject.

After outlining the fundamental principles of FEA, such as defining model geometry, creating finite elements (meshing) and specifying or importing material properties such as B-H curves, the presentation takes a detailed look at aspects especially relevant to rotating electrical machines. These include hysteresis loss, the demagnetisation effects of short-circuits and other faults, and the critical importance of obtaining an accurate representation of the magnetic field in the rotor-armature air gap. Engineers modelling highly complex magnetic gearing systems involving concentric rotating and static magnetic paths are shown how Opera simplifies the task by allowing the definition of multiple air gaps.

The presentation discusses how by setting suitable periodicity boundaries, users can reduce the size of the electrical machine model - and therefore the number of equations that need to be solved - significantly, leading to much faster computation times. This is especially important for designers of high pole count machines, because it enables the analysis model to be a fraction of the full device.

In Opera, current carrying conductors are represented using coils; Opera 3D provides a comprehensive library of standard coil forms such as solenoids, racetracks and bedsteads. If the required coil is not in the library, it can be represented by a continuous combination of bars, arcs and bricks. Scripting facilities enable users to create libraries of commonly used coils for a particular machine very easily.

The increasing complexity of electrical devices means that a model of a motor or generator may not be sufficient to obtain an accurate representation of its behaviour under all operating conditions. The presentation therefore describes how Opera's standard circuit editor enables power electronics and switching circuits to be defined, which then interface with the conductors in the model of the device itself. Simple 'drag and drop' techniques are used to position general circuit representations of voltage and current drives, and components such as resistors, diodes, capacitors, inductors, switches and windings. Specific configurations can be defined in minutes, and used to create a library of common test circuits for use during subsequent analyses.

Mechanical coupling in full rotating machine analyses is functionally similar for 2D and 3D - the coupling data can include the moment of inertia and the frictional speed-varying or fixed applied torque. For solving system-level design problems, rotating or linear motion simulations can be included using Opera as part of the system. Co-simulation with Simulink allows the two simulations to exchange data at each Opera time step, and multiple Opera simulations can be included in the same system simulation. The presentation provides an example of two separate Opera 2D models, for the exciter and generator parts of a system, with Simulink ensuring that both rotate at the same speed, as though they were mounted on a common shaft in real life.

Opera allows users to define any shape of device, magnets and coils - as well as generic electrical circuits - which makes it possible to create 2D or 3D models of virtually any type of linear or rotational electrical machine. These include ac induction, brushed and brushless permanent magnet, ac wound rotor induction and switched reluctance motors, as well as induction, permanent magnet and doubly-fed generators. Specific solvers are chosen to maximise accuracy with the computing hardware that is available; the results file is post-processed automatically, to generate graphic displays of the points of interest. Compared to traditional testing or analytical calculations, these provide a much more powerful tool for making design decisions based on detailed assessment of each component part. Forces, torque, hysteresis and eddy current losses can be calculated automatically, as can variables such as flux linkage, cogging torque, fields and saturation, iron loss, demagnetisation, etc.

The presentation also highlights Opera's multi-physics capabilities, showing how the software can perform thermal and structural analyses, and describes how by use of multiple goal-seeking algorithms it helps optimise the design process, automatically 'homing in' on the best solutions. Designers are also shown how the Optimizer tool can be used within Cobham's Machines Environment - an application-specific extension to Opera - to further accelerate the design process. By making extensive use of templates, drop-down menus and Wizard-style dialog boxes, the environment enables users to fully quantify the motor or generator they wish to design, very quickly and easily.

The presentation concludes with a real-world example of FEA, using the Machines Environment to simulate the permanent magnet motor fitted to the Toyota Prius hybrid vehicle. The simulation results are compared to the test results obtained by the Oak Ridge National Laboratory (ORNL) in the USA, which carried out an experimental characterisation of the motor and its drive system. In order to demonstrate the Machines Environment's ease of use, the simulation task was performed by a relative novice in FEA techniques. After selecting basic design data, such as the type and sizes of magnets, rotor, stator and windings, the user amended the profiles of the magnets, rotor and stator manually, to provide a representative example. The first analysis shows the static torque that the motor generates for various drive currents, which correlates closely with the test results from ORNL, while the next run obtains the cogging torque and torque ripple. The magnetic flux density images obtained from 2D and 3D models of the motor also exhibit a high degree of conformity, demonstrating the accuracy of the simulation.

Design automation software for rotating requirements

Optimal design solutions to rotating electrical machine requirements can now be created in hours, by non specialists, using a new version of design automation software from Cobham Technical Services.

Optimal design solutions to rotating
electrical machine requirements can
now be created in hours, by non specialists,
using the Machines Environment design
automation software from Cobham.

Cobham's Machines Environment introduced a new level of user friendliness when it was launched by providing a design entry system that allows precision finite-element analysis (FEA) models of motors and generators to be created and solved in minutes. The two-dimensional (2D) version of the software has now been integrated with Cobham's unique optimization tool which automatically finds the optimal solution within a design space - even for multiple or competing design objectives.

Cobham's Machines Environment is an application-specific extension to the well known Opera electromagnetic simulation package. It provides a front-end to the simulator that speeds design entry by means of Wizard-style dialog boxes. Users select the style of motor or generator they want to design from a library of all common types, including induction, brushless permanent magnet and switched reluctance motors, and synchronous motors or generators. Then, dialog boxes allow the user to enter parameters to define mechanical geometry, material properties and electrical data, and the FEA model is automatically created.

The use of parameterized models and the ability to quickly load and modify previous designs has always made it possible for users to perform 'what-if?' design investigations. Now, to extend these possibilities to the maximum, Cobham has integrated a unique optimization tool that makes it simple for users to find the best solution across the design space. While auto-optimization tools are not new, they usually require manual intervention if the globally optimal solution is to be found, and the simulation times involved often make this impractical. Cobham's uniquely powerful tool - Optimizer - 'intelligently' selects and manages multiple goal-seeking algorithms including stochastic, descent, particle swarm and Kriging to eliminate the need for manual intervention.

Setting up an Optimizer run from the Machines Environment has now been made as easy as the design entry process. Because most FEA simulations can take as little as a few seconds, the integrated software makes it feasible to thoroughly explore the design space. Thousands of simulations can typically be executed within hours, making the 'perfect solution' achievable for all users - without expert assistance.

"This software makes the high accuracy of finite element analysis available to all engineers, not just the expert with years of experience," says Cobham's Jeremy Howard-Knight. "Even a novice engineer can now create a precision finite element model and find the best solution in a design space, without needing to know much more than what he or she wants to achieve."

The 2D Machines Environment is now in its fourth generation, and Cobham has developed an extensive library of rotating machine design styles, and design components. However, if there are still any unusual features that need to be incorporated in designs, users also have open access to the scripts that generate the models, and can modify them at will to automate proprietary motor and generator design concepts. A library of common material properties is also included in the design software. Again, if users employ any special materials, such as an unusual grade of steel for laminations, then a new menu item can be created within minutes. Cobham will also generate custom scripts for users on request.

Cobham's Machines Environment is expected to appeal to the many users of analytic motor design programs, giving a means of performing much more accurate analysis rapidly and without the engineering overhead usually required for accurate FEA. The tool can deliver significant advantages in today's market environment. Currently, there's enormous pressure to improve energy-efficiency for instance. The combination of highly accurate simulation and sophisticated optimization provides the means to identify the design characteristics of the perfect machine in very short timescales.

A three-dimensional version of the Machines Environment is optionally available.

Multiphysics simulation tool accelerates electromagnetic design projects

The latest Opera electromagnetics simulator 
adds mechanical stress analysis, extending
the tool's multiphysics capability to provide a 
single-step solution to complex design problems.

A powerful new version of the Opera electromagnetics simulator for design engineers has been released by Cobham Technical Services. The latest software adds three-dimensional mechanical stress analysis, extending the tool's multiphysics capability to provide a single-step solution to complex design problems. By capturing mechanical deformation in conjunction with electromagnetic and thermal modelling, the integrated software can greatly reduce design complexity and timescales.

Opera version 15, from the Vector Fields Software business unit of Cobham Technical Services, provides a complete design-simulate-analyze-optimize toolchain for electromagnetic applications. The software is renowned for its accuracy of simulation and speed of execution - allowing demanding simulations to be solved on standard office-grade PCs. It is available in a number of variants that include finite element analysis (FEA) for static and time-varying electromagnetic fields, and application-specific solvers for rotating electrical machines, superconducting magnets, charged particle beam devices, and magnetization/demagnetization processes. Advanced material models, such as lossy dielectric insulation and magnetic hysteresis, put Opera at the cutting edge of simulation capability. Opera’s electromagnetic models may also be coupled with third-party system simulation tools available within Simulink.

The new three dimensional stress analysis module solves for deformations within the elastic limit of the materials, and may be coupled with the electromagnetic solvers to provide a single-step solution to virtual prototyping. In addition to stress and strain produced by the application of mechanical loads and by electromagnetically induced forces, Opera's thermal analysis module may be used to co-simulate thermal expansion. The effects of gravity or rotationally induced forces can also be incorporated in design simulations.

The latest version 15 of the software extends the fundamental performance advantage of Opera for many common design engineering applications. For instance, mechanical deformation is a vital consideration in the design of large and superconducting magnets, and electrical equipment and coils in transformers, motors, generators and actuators. The ability of a superconducting magnet's coils to withstand the mechanical forces generated during a quench, or the mechanical integrity of the stator end windings of a generator subject to a short-circuit condition, are critical design requirements.

Many other enhancements are incorporated in the new release of Opera, to simplify and speed the design process. One of these supports the rapid creation of models of coils, by providing a dynamic pictorial representation of the model under construction, to guide the user as design data is entered. This extends Opera's existing user-friendly approach to creating models of coils (and other common structures) which allows a user to select common forms of construction from a library, and then enter the design data using dialog boxes.

To aid the final optimization of a design, Cobham's Opera software package can be supplied with an advanced auto-optimization tool that has been designed specifically to work with its finite element methods. This tool is able to work out the best solution for one or multiple goals — even when they compete with each other.

New Sales Manager

Cobham Technical Services has appointed Dr Nigel Atkinson as Sales Manager for its Vector Fields Software product lines. He will be based at Cobham's Kidlington site in Britain, and responsible for the worldwide sales of Cobham's electromagnetic design software outside of the Americas. The product range includes the company's renowned electromagnetic design, simulation and optimisation software, Opera for the simulation of a wide range of electromagnetic applications including electric machines, magnets, and charged particle beams, plus the Concerto package for antenna, RF and microwave design.

"This is an exciting time for electromagnetic simulation software providers", states Nigel Atkinson. "In addition to our traditional markets, the renewable power and automotive sectors are undergoing rapid change - with significant growth in the development of wind farms and hybrid vehicles. These are both areas where Cobham's Opera and Concerto software tools are already helping designers shorten development time significantly. With new application-specific design environments being rolled-out as part of Cobham's new software releases in applications such as transformer design, advanced finite-element analysis techniques are now available and accessible to every level of designer. I see tremendous opportunities for growth of our business internationally, particularly in a number of the key Asian economies, as well as further potential to develop our positions in established global markets".

Nigel Atkinson brings extensive knowledge of simulation software, with in-depth technical experience in finite element modelling, including software development, as well as managerial experience in support and sales functions. Prior to joining Cobham, he was a UK Account Manager for a leading engineering simulation software company.

Nigel Atkinson holds a PhD from Bath University (GB), which was awarded for research into the electromagnetic design of MRI scanners - a design field in which Cobham's Opera software is widely used.

"We are extremely pleased to have someone of Nigel's experience join our sales team", says Dr Kevin Ward, Head of Cobham's Vector Fields Software business in Kidlington. "We believe that his technical background in finite element modelling, combined with his commercial knowledge of our potential customer base, will help us broaden our reach significantly."

Enhanced electromagnetic analysis software accelerates RF and microwave design

Concerto speeds simulation of RF designs
employing advanced metamaterials, allowing
representation by bulk properties.
Here, a plane wave strikes metamaterial
with a negative refractive index.

Cobham Technical Services has a new release of the Concerto electromagnetic design software for RF and microwave applications from its Vector Fields Software product line. Concerto provides developers with a very cost-effective means of achieving the best solution in the shortest possible time. The latest version - Concerto v7.5R1 - incorporates numerous enhancements to accelerate further every aspect of design, simulation, analysis and optimization.

Many of the enhancements in this release centre on the powerful 3D geometric Modeller that forms an integral part of all Concerto configurations. This has new meshing options for the finite element (FE) Eigenvalue solver, which can result in significantly shorter solution times, and the Modeller now provides access to a range of additional features in Concerto's finite difference time domain (FDTD) simulation engine. Among these is the ability to present frequency domain field plots over any regions of the model, and for any number of frequencies, from a single time domain analysis.

The Modeller now also supports features for the efficient simulation of complex materials in FDTD. One new facility allows the definition of lumped ports with frequency dispersive properties, based on the Drude, Debye and Lorentz models, providing a circuit element representation of discrete structures within complex materials.

The properties of metamaterials are being explored increasingly for use in microwave devices such as antennas and filters. Support for the simulation of these materials has been enhanced by allowing their representation by bulk constitutive properties. Since these types of materials generally rely on small-scale structure for their desired electromagnetic characteristics, their simulation can be very computationally intensive; using their bulk properties greatly increases the speed of simulation.

One common application of Concerto is in the design of antennas. A new tool in the Modeller enables swept far-field results to be generated by the FDTD solver in arbitrary directions, giving the ability to assess the broad-band far-field performance both on and off boresight.

The Concerto Manager has also been improved, and now features tabbed folder windows for simpler and faster navigation, together with an enhanced capability for running Concerto's frequency domain solvers in batch mode.

Underlying Concerto is an advanced and flexible scripting capability, allowing automation of almost all of the features of model creation analysis and post processing. The latest release extends the range of commands and features in the scripting language, and provides a redesigned and enhanced editor for creating and editing command files.

Concerto provides an FDTD simulator as standard, enabling users to quickly and easily model a wide variety of microwave devices such as antennas, waveguides, filters, cavities and resonators. Two further simulation options are available. A Method of Moments (MoM) analysis module uses a highly accurate formulation for the analysis of arbitrary geometries. Typical applications include radar cross-section calculation and the evaluation of antenna performance and placement on aircraft and ships. For designers wishing to characterize the performance of devices such as RF cavities and microwave resonators, Concerto offers a Finite Element Method (FEM) analysis module, which determines the eigenvalues and associated eigenvectors of resonant structures.

Concerto v7.5R1 is available in a number of configurations, including several low-cost versions, all of which use the 3D geometric Modeller for model build or import and employ the FDTD solver as standard. These versions can be upgraded to the full professional version at any time. Concerto ES is an entry-level 3D package which provides an ideal introduction for designers who are new to virtual prototyping software. Concerto 2D is an extremely fast 2D analysis module, which is primarily intended for designing components with axisymmetric geometries, such as circular and corrugated horn antennas. For designers of axisymmetric coaxial devices, such as connectors, Concerto AS offers a highly cost-effective means to optimize their electromagnetic designs very quickly.

MagLab uses field simulator

Field measurements on SCH electromagnetic shields

Cobham Technical Services' Opera 3D electromagnetic field simulator is playing a vital role in the design of an innovative hybrid magnet being developed by the USA's National High Magnetic Field Laboratory (NHMFL) in Florida.

The NHMFL - popularly known as the MagLab - is home to some of the largest and most powerful laboratory magnets in the world. Headquartered in a 370,000-square-foot complex at Florida State University, the facility provides scientists and engineers with a unique environment in which to conduct experiments involving very high energy magnetic fields.

Many of the innovative magnets used at the MagLab are designed and built on-site, by the facility's Magnet Science & Technology group. One of the latest additions, currently early in its construction, is a Series-Connected Hybrid (SCH) magnet designed to provide unprecedented power efficiency and field homogeneity. Development of this resistive-superconducting hybrid magnet is being funded by an $11.7 million grant from the US National Science Foundation, and the magnet will be used for research purposes in high field nuclear magnetic resonance (NMR), condensed matter physics, biology and chemistry.

The SCH uses a water-cooled Florida-Bitter resistive magnet - a highly innovative technology developed by the MS&T group, capable of generating high magnetic field strengths more efficiently than alternative means - nested within a superconducting magnet that is cooled by liquid helium. The two magnets are connected in series and together create a very high intensity central magnetic field of 36 tesla. The SCH is connected to a 650 V supply and has an operating current of 20,000 A; this 13 MW power consumption is 66 percent less than what would be required for an all-resistive magnet providing the same field and bore.

The Opera-3D electromagnetic simulator from Cobham Technical Services was used to aid the design of the SCH magnet and its shielding.

Electromagnetic shielding of the SCH is provided by a set of eight magnetically soft, 100 mm thick iron plates which form an octagonal wall around the entire magnet system. The magnetic properties of these shields were characterised by a B-H curve, obtained by using Opera 3D.

According to Iain Dixon, Research Associate at the Magnet Science & Technology division, "We chose to use Opera v12.0 to evaluate the 3D magnetic field uniformity and fringe fields of the SCH because the simulator is accurate and fast. The inner coils of the SCH are of Florida-Bitter type with essentially non-uniform current densities. To emulate this, we subdivided each coil into a large number of radially thin coils with uniform current densities, and the whole coil system was generated by use of an external program called by Opera from command line."

Opera 3D has also been used for a variety of other performance-related studies on the SCH, including evaluating the magnetic fields around the magnet's HTS (high temperature superconductor) vapour-cooled leads, and calculating eddy currents in the thermal radiation shields surrounding the superconducting coil. In the latter case, these calculations are of critical importance; during fast discharge of the magnet - such as in the case of a quench - eddy currents can exert large mechanical forces on the shields, and they therefore need to be accurately simulated for safety.

The SCH promises to set a new standard in powered magnet performance. Its efficiency means that it will have a lower operating cost than any other magnet in its class, and its innovative magnet configuration should provide an unprecedented level of field homogeneity and stability. Such is the design expectation that the MagLab is already involved in two further variations of the SCH; one other under construction is destined for the Helmholtz Zentrum Berlin (D) where it will be used for neutron-scattering experiments, the other in design is for the Spallation Neutron Source at the Oak Ridge National Laboratory in Tennessee (US).