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Mechanically Operated Interrupting Devices with Arc Suppression

IP.com Disclosure Number: IPCOM000178169D
Original Publication Date: 2009-Feb-13
Included in the Prior Art Database: 2009-Feb-13

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

Interrupting devices, such as mechanical switches and magnetic relays, are widely used to control the flow of a current in electrical circuits. The contact system in such a mechanical switch includes an energizing contact. When cutting off high currents, this contact has to withstand severe breaking arcs, and the consequent ablation of contact material reduces device endurance. This results in a limitation of the interrupters breaking capacity. Nevertheless, improvement to breaking capacity is desired in order to enhance control of more powerful devices.

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Mechanically Operated Interrupting Devices with Arc Suppression

Idea: Yi Rong Yang, CN-Shanghai; Zhao Hui Du, CN-Shanghai; Jian Guo Ma, CN-Shanghai; Stefan
Cordes, DE-Nuremberg

Interrupting devices, such as mechanical switches and magnetic relays, are widely used to control the flow of a current in electrical circuits. The contact system in such a mechanical switch includes an energizing contact. When cutting off high currents, this contact has to withstand severe breaking arcs, and the consequent ablation of contact material reduces device endurance. This results in a limitation of the interrupters breaking capacity. Nevertheless, improvement to breaking capacity is desired in order to enhance control of more powerful devices.

Prior contact systems designed for sequential breaking of electrical circuits have at least two contact points; one point is called the energizing contact, and the other is called the auxiliary contact. Generally, these two contact points share a common switchable electrode. This type of configuration is simple and allows the sequential breaking requirements to be easily fulfilled by using dimensional asymmetries such as different gaps, angles, or contact areas. The separations of the two contacts can be controlled individually by managing the common electrode. In these configurations, the circuit making sequence is the reverse of the circuit breaking sequence. In the circuit breaking sequence, the energizing contact opens before the auxiliary contact as required. However, in the concomitant circuit making sequence, the energizing contact always closes after the auxiliary contact. This circuit making sequence causes an inrush current. If the auxiliary contact closes before the energizing contact, the current immediately increases because the transition device provides a highly conductive path. Subsequently, the transition device is triggered to reduce conductivity, and the current drops dramatically. When the energizing contact closes later, the current again increases in the loop creating an inrush current, which potentially may harm the equipment. Figure 1 shows three prior embodiments. Two contact points are composed of two fixed electrodes and one movable shared electrode. The difference in some of the dimensions of the two contact points, such as gaps or angles or contact areas, cause sequential circuit breaking to occur when the common electrode moves or rotates. It is desirable that the time constant of the transition device is small enough to allow the interrupting device to switch off the current in a short time. The transition device should have no dependency on ambient temperature to allow the interrupting device to have broad temperature range. Furthermore, sufficient electrical endurance of the transition device will ensure the life span of the new device. All known contact...