At CWIEME, Cobham Technical Services is releasing a new version of its Vector Fields Software tool for designing rotating electrical machinery. The electromagnetic simulation software combines the accuracy of virtual prototyping using finite-element analysis with a rapid front-end design tool that allows users to create models of motors and generators in minutes — allowing users to achieve radical new levels of development productivity.
Several new modelling elements are being added to accelerate the design process. The company is also showing an optional new hysteresis solver for soft magnetic materials that provides an accurate means of accounting for losses and predicting performance changes due to hysteresis effects in the specialty electrical steels that are increasingly being used to enhance machine efficiency.
The software is an application-specific toolbox for the well-known Opera Vector Fields Software package, and provides a front-end to the electromagnetic simulator that speeds the creation of design models by means of ‘fill in the blanks’ dialog boxes. Users select the form of motor or generator they want to design from a list of all common types. By simply entering a list of parameters to define mechanical geometry, material properties and electrical data, a model is automatically created and post-processing performed.
The package comes with templates for a broad range of common rotating machinery including motor types such as AC induction, brushless, permanent magnet and switched reluctance, plus synchronous motors or generators. Within these basic equipment types, users can choose from a wide selection of component geometries and other options to create their design.
Among several new model elements added with this release is an embedded magnet design plus variants of a V-shape rotor magnet – a style used to achieve higher torque densities as well as being less prone to demagnetisation. There is also a new template for permanent magnet generators. These options give users the means to quickly create a model, even for manufacturers who have their own proprietary design techniques. Among a number of other enhancements to the design package is a more powerful post processor tool, to perform calculations and manipulations on simulation results to analyse a design concept.
If there are any unusual features that need to be incorporated in designs, users also have open access to the scripting codes that generate the models, and can modify them at will to create a proprietary automated design process. A library of material properties is also included in the design software for speed, and is selected by means of a drop-down menu. Again, if users employ any special material, such as an unusual grade of steel for laminations, then a new material characteristic can be created within minutes and imported into the model.
“Finite element techniques allow users to simulate design ideas with supreme precision and accuracy, but it can take many hours to build a model of something as complex as a motor,” says Alex Michaelides of Cobham Technical Services. “This software provides a precision virtual prototyping capability that allows searching ‘what-if?’ investigations to be performed in minutes, to identify the design characteristics of the perfect machine.”
Cobham Technical Services’ two-dimensional modelling and simulation design tool provides a very cost effective entry point to the accuracy and power of finite element analysis modelling, and offers a very flexible upgrade path from the analytic computer programs that many motor and generator manufacturers currently use.
Numerous options provide further sophisticated support for design optimisation. These include a solver to simulate the dynamic rotating machine, and an ‘intelligent’ optimisation tool that automatically selects and manages multiple goal-seeking algorithms to find the best solution to a design problem. A brand new hysteresis solver is also now available. This new tool provides a solution for one of the last major barriers to optimising the energy efficiency of machinery; it can also help to improve the accuracy of hysteresis motor designs.
The modelling of hysteresis effects in soft magnetic materials is a complex problem that electromagnetic tool suppliers have largely ignored, with the result that machine designers are forced to neglect small remanent magnetic fields that are created by the pulsing or rotating actions of dynamic machinery. If hysteresis effects are considered, it’s usually done by means of some post-processing prediction based on a simplistic model. Cobham Technical Services’ new Hysteresis Solver employs actual measured magnetic characteristics. The turning points of the BH (magnetic induction, and applied field) trajectories are used to predict the behaviour of arbitrary minor hysteresis loops, providing a good approximation of true physical behaviour without requiring extensive computation, and additionally making only realistic demands for materials data. The tool is provided with ready-to-use characteristics for some common silicon steel materials. This library can be expanded easily using data from a manufacturer’s datasheet, or by real-world measurement.
“There’s a great deal of opportunity in the motor and generator sector at the moment for designs that can bring new levels of efficiency to the market,” adds Alex Michaelides of Cobham Technical Services. “Advanced design support in the form of finite element techniques is currently employed only by a proportion of manufacturers. This application-specific finite element tool provides a very cost effective means of both enhancing and speeding the design process for innovative companies.”