Svein Thore Hagen

High Current Arc Erosion on Copper Electrodes in Air

An arc fault inside metal enclosed switchgear will cause the pressure to rise and vaporization of electrode material may contribute to the pressure rise. An experimental study of high current arc erosion on copper electrodes in air has been performed, with an evaluation of fraction lost by gross melting and vaporization. All experiments were performed at NEFI High Voltage Laboratory in Skien, Norway. The measured mass loss from vaporization in our experiments seems to be negligible compared to erosion by gross melting.

Small-Scale Arc Fault Testing of Medium-Voltage Metal-Enclosed Switchgear

Internal arc fault tests are important for ensuring the safety of medium-voltage metal-enclosed switchgears. Since these tests are conducted at full scale, the costs of the test objects as well as the high-power laboratory are significant. This paper presents an experimental study to clarify whether such tests can be simplified by downscaling. Tests with volume and energy downscaled to 1/3 and 1/10, respectively, were performed on a single-phase arrangement with air as the insulating gas. The test results showed that the internal pressure rise caused by the arc can be reproduced well using a smaller compartment and lower current. The potential damage caused by the exhaust of the hot gas escaping through the pressure-relief openings is more challenging to predict from small-scale tests.

Modeling and optimization of coolant channel cross sections in induction heating coils

NOTICE: This is the author’s version of a work that was accepted for publication in Compel. A definitive version was subsequently published in Compel 30(2011) No 5, DOI http://dx.doi.org/10.1108/03321641111152702

Results of the cooperative learning program at Telemark University College, Norway

In 1982, the forerunner of the engineering school of Telemark University College adapted a version of project based learning program of the Aalborg University as their sole pedagogical method, the Telemark Model. Based on 20 years of positive experience with the Telemark Model, a pioneering project was launched in 2002 on recruitment with graduates from classes at vocational schools. In 2004, a program for student enterprise was added with astounding results. In 2008, the engineering school of Telemark University College was awarded the First Prize for Quality in Education by the Ministry for Education and Research for the development and quality assurance of this project. In addition, their student enterprises have been awarded 30 prizes, including 5 prizes in the European championship contests. After a brief historical presentation, the paper will describe, discuss, and relate the results of the Telemark Model. These results include better recruitment, student retention, improved college finances, and most important - a good academic standard of graduates nationally as well as internationally. Finally, it will be discussed if the sum of these experiences can pave the way from interdisciplinary into transdisciplinary thinking and methods.

Thermal measurements for service life estimations of high power induction hardening coils

The temperature profile of an induction coil is an important factor in the estimation of induction coil service life. Coil surface temperatures are measured in an improved experimental setup by a thermographic camera. Temperatures are measured on three cross sections commonly used in induction heating coils at varying current levels and varying coolant flow rates. The measurements are compared with previous measurements and to a numerical model. In general good agreement is found between measurement and model, but important differences were found. These differences are discussed.