Download Coupled Field Problems in Electrical Apparatus

INTERNATIONAL SYMPOSIUM
ON NONLINEAR MECHANICS
6th ISNM NSA NIŠ '2003
Faculty of Mechanical Engineering
University of Niš
18000 - NIŠ, A. Medvedeva 14
Tel.: (+381 18) 524-915
Coupled Field Problems in Electrical Apparatus
Ivan Yatchev
Technical University of Sofia
Department of Electrical Apparatus
1156 Sofia, Bulgaria
E-mail: [email protected]
Introduction
In order to model and design real devices it is very often necessary to solve
coupled field problems. In electrical apparatus, the electromagnetic field is the main
one. The coupled problems encountered in electrical apparatus are most often
coupling the electromagnetic field with:
- thermal field;
- electric circuit;
- mechanical motion;
- stress analysis problems;
- fluid dynamics problems.
Very often more than one problem has to be considered, e.g., the electric circuit
is existing in almost all apparatus.
In the present paper, some examples of these problems are considered in more
details and some results are presented.
Coupled problem electromagnetic field – electric circuit – thermal field
A coupled three-dimensional problem of the above mentioned type is
considered for electromagnet of an AC contactor. Finite element method has been
employed for solving the problem. General-purpose CAD system is employed for
the data input. The coupling is performed in indirect way – by successive solutions
of the field-circuit and thermal problems. Results are obtained for steady-state.
Coupled problem electromagnetic field – electric circuit – mechanical motion
A coupled problem electromagnetic field - electric circuit - mechanical
motion has been considered and solved for a solenoid actuator. The algorithm for the
solution of the problem has been presented. The electromagnetic field has been
modelled using finite element method. Non-linearity is handled using NewtonRaphson method. The electromagnetic force is computed with the help of Maxwell
stress tensor. Backward Euler method has been used for integration in time of the
resulting system of equations. The results obtained are verified experimentally.
Coupled problem electromagnetic field – mechanical motion – electric arc rotation
A particular coupled problem is considered for rotating arc SF6 circuit
breaker. The process of interaction between the magnetic field and the electric arc
rotating in fluid during the current interruption has been studied. The finite element
method has been employed for the magnetic field and the interaction between the
magnetic field and the electric arc taking into account the motion of the moving
contact. Results are obtained for magnetic flux density and electromagnetic force,
acting on the arc.
Conclusion
Several coupled problems encountered in electrical apparatus are presented,
mainly of electromechanical nature. The solution of coupled problems is of major
importance for the adequate modelling and design of electrical apparatus. Although
a lot of research efforts have been employed in this area, there are still problems that
are open to be solved.