Electromagnetic simulation advance helps electrical machinery designers to achieve ultimate efficiency

Vector Fields, a part of Cobham plc, has extended the accuracy of its Opera electromagnetic simulator for electrical machinery applications with a new finite-element hysteresis solver for soft magnetic materials. Believed to be unique, the new Hysteresis Solver provides designers of motors, generators and other electrical machinery with 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.

Improving the energy conversion efficiency of electric motors and related products is probably the single most important design focus for today’s electrical machinery suppliers, and hysteresis effects are typically responsible for the majority of the inefficiencies that remain to be overcome.

The modelling of hysteresis effects in soft magnetic materials is a very 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. Such approaches can be highly inaccurate, especially when non-sinusoidal excitation is used, and when there are pronouced non-linear effects involved – such as detent torque.

In the drive towards higher efficiencies, many machine designers are employing more efficient ferromagnetic alloy materials for laminations. Vector Fields’ new hysteresis solver tool provides the means for designers to accurately simulate the dynamic performance of these materials. In conjunction with the sophisticated design-simulate-optimize capability offered by the finite element analysis tool, this provides developers with the means to fully understand the improvements that electrical steels can make, as well as to explore mechanical design ideas that minimize hysteresis effects.

The hysteresis solver is available as part of the general-purpose Opera simulation tool-suite for static and transient electromagnetic design, or in Vector Fields’ application-specific tool for motor and generator design — Opera Electrical Machines Environment. Among the product sectors that can be enhanced using the tool are dynamic electrical machinery such as motors and generators, as well as actuators and transformers.

The new capabilities of Opera are also expected to appeal to the specialist segment of the motor market, which manufactures hysteresis motors and brakes. The lack of commercial finite element based hysteresis simulation tools means that developers of equipment which relies strongly on hysteretic effects have typically used less accurate analytic design techniques. The finite element analysis Opera system with the improved hysteresis solver now offers such companies access to a highly automated design platform that can not only optimize the efficiency of existing designs, but also radically expand the range of design ideas that can easily be explored.

Vector Fields’ new Hysteresis Solver is based on actual measured BH (magnetic induction, and applied field) characteristics. The turning points of the B(H) trajectory 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 using an Epstein Frame (the standardised device for measuring the magnetic properties of electrical steels).

The new hysteresis solver complements Vector Fields’ long-standing DEMAG electromagnetic modelling software for simulating the characteristics of permanent or hard magnet materials. This solver allows designers to optimize equipment designs by accurately simulating both the magnetization process, and the subsequent demagnetization effects that might be encountered, and is widely used by magnet suppliers and producers.