Design of Shading Coils for Minimizing the Contact Bouncing of AC Contactors
ABSTRACT For many decades, electromechanical contactors have been widely used in the industry, and over 80% are equipped with AC powered coils. Electromechanical contactors have the drawback of the mechanical movement of some of their parts and the wear related with it. This movement causes the contacts to impact during closure, producing a bouncing of the contacts and consequently the estimated life of the contacts is dramatically reduced. The coil of the contactor can be powered by an AC or a DC supply. When dealing with DC powered coils, they generate a constant magnetic field that guarantees an appropriate closing of the contacts. However, AC powered coils generate sinusoidal magnetic fields which produce a force that drops to zero twice each cycle (50/60 Hz). This creates an undesired chatter or pulsation of the contacts. This harmful effect can be cancelled by using a shading ring placed in the contactor core. In a well- designed shaded pole contactor the magnetic force should never drop below the springs force in order to avoid the chattering of the contacts. In this work the influence of shading rings parameters on the behavior of the dynamic response of the contactor is studied and results are presented.
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ABSTRACT: Due to the fringing effect, magnetic flux in the air gap of electrical machines is reduced. This leads to enlarged effective air gap length. Currently, the Carter coefficient is applied to compensate the slot effects. This coefficient is calculated with respect to the slot dimensions and air gap length, using Carter formulas and corresponding curves. These curves are taken by solving the two dimensional Laplace equation for voltage, and cannot be accurate (errorless) completely. Nowadays, using FEM (finite element method) packages of numerical methods, slot effects on the air gap flux distribution are calculated carefully. In this paper using the ANSYS package of FE, these effects are studied. Using the results of these studies and comparing them with the Carter method, the Carter coefficient is modified.Electronics, Circuits and Systems, 2003. ICECS 2003. Proceedings of the 2003 10th IEEE International Conference on; 01/2004
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ABSTRACT: The authors describe the modeling of the transient dynamic behavior of a solenoidal core type electromagnetic actuator using an overlapping finite element (FE) scheme. The FE scheme allows two topologically unconnected 2D finite element meshes to slide over and overlap each other, whilst still coupled together electromagnetically in a consistent manner. The result is that the same set of FE meshes can be used to model directly a continuously shrinking or expanding air gap. This paper demonstrates, for the first time, that such a FE scheme can be used to model accurately the dynamic closing of the air gap of a linear actuator. The results of the simulation were compared with experimental measurements. It is shown that good agreement between simulated and measured results is obtainedIEEE Transactions on Magnetics 08/2000; DOI:10.1109/20.877714 · 1.21 Impact Factor
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ABSTRACT: A number of possibilities for constructing table-based lumped-parameter models of linear or rotary actuators are compared. Two of them have not been published previously. The accuracy of the models is evaluated by comparing simulated results against experimental measurements taken from a prototype actuator. The computational cost of the models is also discussedIEEE Transactions on Magnetics 04/2002; DOI:10.1109/20.996245 · 1.21 Impact Factor