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The Magnetic Material Man Jiles to KTH

Published Jun 11, 2010

With magnetic cooling, environmentally hazardous freon gas and other cooling agents can disappear from our fridges. David Jiles is coming to KTH to talk about material for magnetic cooling as well as material that can, among many other talents, independently set the focus on cameras and reduce vibrations in cars. However his magnetisation model has now received a challenge from doctoral students at KTH.

David Jiles, Wolfson Centre for Magnetics, Cardiff University
David Jiles, Wolfson Centre for Magnetics, Cardiff University

Research by David Jiles from the Wolfson Centre for Magnetics, Cardiff University, has led to many applications in our society. Magnetic cooling is his next contribution which may lead to the disappearance of freon, an environmentally hazardous gas, from our homes. He is also participating in the development of magnetic material that can change shape by itself, known as magnetostrictive material. Form change when the material is magnetised can amount to one whole percent.

“The material works like a muscle and so does the entire job itself. This can form a valuable complement to hydraulics or conventional electro mechanics,” states Göran Engdahl, KTH Professor of Electrotechnical Design, who took the initiative for this lecture.

This shape-changing magnetic material has many areas of application. It can be used to set the focus of lenses, reduce noise levels from machines as well as in underwater loudspeakers or for vibration control in apparatus that wear out from vibrations, or to reduce vibrations in cars.

Göran Engdahl, Professor of Electromagnetic Engineering
Göran Engdahl, Professor of Electromagnetic Engineering

David Jiles is best known for his model of magnetic material that is used in most commercial computation programs for dimensioning of magnetic apparatus such as power transformers. However, Göran Engdahl feels that this model is not perfect. When David Ribbenfjärd presents his doctoral thesis in one week’s time, he will be the third consecutive doctoral studies student at the Division of Electrotechnical Design who has carried out research on the development of a more comprehensive model. Jiles will be his examiner at the public defence of his thesis.

“The driving force behind the development of a new model is that Jiles’ model shows certain deficiencies,” states Göran Engdahl who is David Ribbenfjärd’s thesis supervisor and who has run three research projects financed by EU within the field of applications of magnetostrictive material.

In his thesis, David Ribbenfjärd has further developed the modelling of power transformers.

What is new in Ribbenfjärd’s model?

“His power transformer model includes all loss mechanisms in the magnetic core and coil such as static hysteresis, eddy currents anomalous magnetisation losses, and the coil phenomena eddy currents, capacitive effects and leakage flux,” states Göran.

David Jiles’ lecture entitled “Recent progress in magnetoelastic and magnetocaloric materials” will be held on 18 June, 1.15 – 3 p.m. in Room D3, Lindstedtsvägen 5.

Read more about David Jiles’ lecture

Read more about David Ribbenfjärd’s thesis and defence

More information, contact Göran Engdahl, 08-790 7760,

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Belongs to: Electromagnetic Engineering
Last changed: Jun 11, 2010