Shokichi Ito

3-D finite element analysis of electrodynamic repulsion forces in stationary electric contacts taking into account asymmetric shape

The quantitative characteristics of stationary electric contacts in electrical apparatus have been given by means of some calculations, based on an artificial model of the current flow lines which highly simplifies the treatment. We have developed a 3-D finite element method by which the static characteristics of the electric contacts having asymmetric shapes can be analyzed. Repulsion forces in the stationary electric contacts with rectangular solid contact members as well as ones with cylindrical contact members are calculated by our method. The validity is confirmed by comparing with the results by the well-known Holm formula.

Numerical analysis of dynamic characteristics of electromagnets using 3-D finite element method with edge elements

This paper describes a new method for the accurate computation of the dynamic behavior of DC and AC electromagnets, such as used in contactors, relays and other electromagnetic devices. The method is based on the 3-D finite element method with edge elements taking into account the nonlinearity of the cores and the eddy current. For the dynamic analysis, it is necessary to change the 3-D meshes automatically. The analyzed model couples electrical, magnetic and mechanical systems of the electromagnets. Our method makes it possible to predict dynamic characteristics for the optimizing design of electromagnets. The validity of the new method is confirmed by experiments. >

3-D finite element analysis of operating characteristics of AC electromagnetic contactors

AC electromagnets are widely used for electromagnetic devices. It is necessary to predict the dynamic behavior for the optimum design of AC electromagnets. The 3-D analysis method has been used to obtain the operating characteristics of an AC electromagnetic contactor. The electromagnet of the contactor has a complex load curve relating to the position of the armature. The time variations of the exciting current and the stroke of the electromagnetic under the load are calculated by our method. It is clarified that of the operating characteristics of the electromagnetic contactor can be accurately calculated by comparing it with the measurements. >

Numerical analysis of electromagnetic forces in low voltage AC circuit breakers using 3-D finite element method taking into account eddy currents

It is necessary for the optimum design of low voltage circuit breakers to analyze electromagnetic forces acting on the contact systems when the circuit breakers interrupt fault currents. In this paper, the forces which are known as the magnetic blowout force acting on the arc and the electromagnetic repulsion force acting on the moving contact arm are obtained by using the 3-D finite element analysis taking into account eddy currents. It is shown that our 3-D analysis is capable of evaluating a new design of contact systems in low voltage ac switching devices.

Heat analysis of a fuse for semiconductor devices protection using 3-D finite element method

This paper describes numerical analysis of the transient temperature rise of the fuse elements in current-limiting fuses for protecting semiconductor devices such as semiconductor power diodes and thyristors from short-circuit faults. The transient temperature rise is obtained by using 3-D finite element method combining the analysis of current distribution in the fuse with the heat analysis of the fuse. The calculated results show good agreement with the experimental ones. It is shown that this 3-D analysis method is capable of evaluating a new design of current-limiting fuses instead of the conventional trial and error approach.

3-D finite element analysis of repulsion forces on contact systems in low voltage circuit breakers

Low voltage circuit breakers which interrupt fault currents rapidly are widely used in power distribution systems. It is necessary, for the optimum design of circuit breakers, to analyze electromagnetic forces on the contact systems equipped with arc rupturing parts. In this paper, the forces generated by currents and flux densities are obtained by using the 3-D finite element method taking into account current constriction and variations in arc diameter. It is shown that the 3-D analysis is capable of evaluating new designs of LV circuit breaker contact systems.

Finite element analysis of magnetic circuits composed of axisymmetric and rectangular regions

A new approximate method is developed for calculating three-dimensional magnetic fields in magnetic circuits composed of connected axisymmetric and rectangular regions. Using this new method, fairly accurate solutions can be obtained when the leakage flux from the magnetic circuit is small. In this paper, the new method is explained and then the usefulness of the technique is clarified by comparing calculated and measured flux densities.

3-D finite element analysis of magnetic blowout forces acting on the arc in vacuum circuit breakers

Vacuum circuit breakers are widely used in medium voltage power distribution systems because of being compact, lightweight, and having long electrical life without maintenance. It is necessary, for the optimum design of vacuum circuit breakers, to analyze blowout forces acting on the arc in vacuum chambers. In this paper, the forces generated by currents and flux densities are obtained by using the 3-D finite element analysis, taking into account the current distribution in current-carrying conductors. The effects of the inclination of slots and position of the arc on the blowout forces are clarified.

Numerical analysis of axial magnetic field acting on the arc in vacuum circuit breakers by 3-D finite element method taking into account eddy currents

It is necessary for the optimum design of vacuum circuit breakers with axial magnetic field electrodes to analyze the residual magnetic field between the contacts in vacuum chambers at the instant when the arc current becomes zero. The residual magnetic field is generated by the eddy currents flowing in the electrodes. In this paper, the residual magnetic field is obtained by using a 3-D finite element analysis taking into account eddy currents. It is shown that the eddy currents are greatly influenced by the configuration of the electrodes, for example the number of slits in the contacts.

3-D finite element analysis of magnetic blowout forces acting on the arc in molded case circuit breakers

It is necessary, for the optimum design of molded case circuit breakers, to analyze magnetic blowout forces acting on the arc in the contact systems when the circuit breakers interrupt fault currents. In this paper, the forces generated by the arc current and the flux density are obtained by using 3-D finite element analysis, taking into account the current distribution in the current paths and variations in arc diameter. It is shown that this 3-D analysis approach is capable of evaluating new designs of contact systems in molded case circuit breakers.