Browse all Theses and Dissertations

2007

Thesis

Degree Name

Master of Science in Engineering (MSEgr)

Abstract

Time varying currents within winding and core conductors induce magnetic fields. When more than one conductor is present the resultant magnetic field can be found by adding the individual magnetic fields by superposition. The resultant magnetic field in turn induces eddy currents within each electrical component within the vicinity of the resultant magnetic field. Eddy currents flow in the opposite direction of the primary current and increase the resistance by reducing the area in which the primary current has to travel. Eddy currents also reduce the effectiveness of the conductors to conductor high frequency currents. Skin and proximity effects were numerically investigated for two parallel plate conductors while a laminated core was designed to reduce the power losses. Maxwell's equations were solved to obtain analytical equations for magnetic fields eddy current distribution and power losses. These equations were illustrated in MATLAB for various frequencies to validate the theoretical analysis. Results demonstrate current within an isolated conductor flows near the surface. However, when the same conductor is placed near another conductor the flow path is affected. For the case when the current is flowing in the opposite direction the magnetic fields are added in the area between the conductors and subtracted on the outer side of the conductor. This causes an increase of the current density within the conductor areas, where the conductors are close to each other. This is the proximity effect. The anti-proximity effect occurs when two conductors carry current in same direction. In this case the magnetic fields are subtracted from each other in the area between the conductors and are added to each other in the area outside the conductors resulting in a higher current density in these areas. The eddy currents can be reduced in two ways. Using a highly resistant material for the core increases the skin depth making the distribution of the magnetic flux more uniform. Laminating the core with an oxide film can be used to reduce the eddy current loss as well. The study shows that the eddy current power loss in a sold core is greater than loss in a laminated core by a factor of K2, where K is the number of the sheets in the laminated core.

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Department or Program

Department of Electrical Engineering

2007

COinS