Contact system of circuit breaker

Abstract

The invention relates to a contact system of a circuit breaker. The contact system comprises a plurality of contact fingers, contact springs and a contact support, wherein two sides of the contact support are fixed by splints; isolation grating sheets are arranged on the contact support; the plurality of contact fingers are connected together by a shaft; two ends of the shaft are supported by holes in the two splints; the contact springs are arranged in gaps between the stomachs of the contact fingers and the isolation sheets; the contact system is characterized in that: more than one contact finger forms one group; and each group of contact fingers share a group of contact springs. By the contact system, the shorttime withstand current of the circuit breaker can be increased and the whole service life of the circuit breaker can be prolonged.

Description

technical field [0001] The invention relates to a circuit breaker contact system, which belongs to the field of electrical switches. Background technique [0002] Circuit breakers are the most important power distribution equipment in low-voltage power distribution systems. With the continuous improvement of power engineering requirements for power supplies and power transmission and distribution equipment, the performance requirements for circuit protection switches are also getting higher and higher, miniaturization, high Performance, modularization, and high reliability are the main development directions of air circuit breakers at this stage. The contact system is an important part of the circuit breaker. The design of the contact spring parameters and the final pressure value of the contact in the contact system is very critical, which is directly related to the short-term withstand performance of the circuit breaker. Improving the short-term withstand current value of...

AI Technical Summary

Problems solved by technology

Universal circuit breakers generally work continuously (24-hour uninterrupted work), and long-term energization leads to high temperature of the contact parts (the surface temperature of the contact fingers may exceed 100°C)

If thermosetting plastics with high temperature resistance, arc resistance, and high structural strength are used to manufacture isolation grid sheets, due to the limitation of thermosetting plastic molding process conditions, its thickness cannot be made very thin (generally required to be ≥1.2mm), and the above can not be achieved. structure

However, when thermoplastic materials are used to manufacture barrier sheets, the structural strength of thermoplastic materials will decrease when the temperature is high, and the barrier sheets will become soft, causing the fingers to shake left and right or even have a large displacement

The movement of the contact finger causes the contact spring pressed in the groove of the abdomen of the contact finger to be skewed, resulting in a decrease in the effective compression of the contact spring when closing, a decrease in the final pressure of the contact, an increase in the contact resistance, and the contact and the entire open circuit The temperature rise of the circuit breaker increases, on the one hand, the resistance to welding of the contacts is reduced; on the other hand, the temperature rise of the circuit breaker is too high, which greatly reduces the design effect

And because of the increase of parts, the structure is too compact, which makes installation difficult and it is not easy to realize automation

[0004] In addition, increasing the contact index in a limited space, excessive contact number and too thin contact finger thickness lead to the restriction of the middle diameter of the contact spring pressed on the belly of the contact finger, resulting in an excessively large height-to-diameter ratio of the contact spring

However, when the contact spring works continuously for a long time, the spring is always in its limit pressure state, so the spring is easy to fail prematurely due to fatigue, resulting in the reduction of the pressure of the contact spring on the contact finger at the closing position, that is, the final pressure of the contact Reduced, and then the short-term withstand current decreases, the range of selective protection becomes smaller, and the accuracy of extremely poor coordination decreases or fails

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