Factors affecting circuit breaker performance

Update date:2018-05-03 Source:MAXGE

Factors affecting circuit breaker performance

There are many factors that affect the performance of circuit breaker products, which can be roughly divided into factors such as the impact on the circuit breaker's current carrying capacity, the impact on the circuit breaker's protection performance, and the impact on the circuit breaker's short circuit characteristics.

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1. Circuit breaker current carrying capacity

Under normal conditions, the ampacity refers to the maximum operating current allowed by the circuit breaker, ie, the rated current of the circuit breaker. However, in some special circumstances, if the ambient temperature is too high, it is necessary to lower the rated operating current, that is, to reduce the current carrying capacity, so that the circuit breaker can work normally at this temperature, the specific current value after the adjustment is in the circuit breaker product design. And the application needs to be considered. For a complete set of equipment, the rated current specified in the complete set of equipment is the maximum operating current of the main switch breaker, and the rated current of the circuit breaker is not necessarily equal. The most direct reflection of the general ampacity is the temperature rise of the circuit breaker terminal, and there are strict regulations on the temperature rise in the national standard. For a complete set of equipment, the maximum temperature rise limit cannot exceed 70K, so the carrier flow affects the performance of the complete set of equipment products. The low current-carrying capacity causes the utilization rate of the circuit breaker in the complete set of equipment to be too low and the economic efficiency is not good. An excessively high current carrying capacity will cause the temperature rise of the device to be too high and damage the insulation of the complete set of products. Therefore, determining the factors that affect the current carrying capacity has a very important significance for the design and application of circuit breaker products in complete sets of equipment.

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2. Circuit breaker protection performance

Circuit breaker protection performance can be divided into overload long delay protection, short circuit delay protection, short-circuit instantaneous protection, under-voltage protection and single-phase ground protection (ground leakage current). Circuit breakers, as an important component in complete sets of equipment, play a role in turning on and off circuits, and are a means of protecting circuit safety. Therefore, the protection performance of circuit breakers is also a very important performance indicator of circuit breakers. Among them, the circuit breaker overload long delay protection refers to the ability of the circuit to break the circuit when it exceeds a certain limit value of the rated current of the circuit breaker. The specified limits are all determined according to the rated current of the circuit breaker. When a circuit breaker is used in a complete set of equipment, the current carrying capacity will generally be reduced. Therefore, when designing and applying a complete set of equipment, the relevance between the setting of the overload protection of the circuit breaker and the actual ampacity must be taken into account. Otherwise, it is not easy to avoid overloading the circuit. Timely trips cause safety accidents and cause unnecessary economic or property damage.

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3. Short-circuit characteristics of the circuit breaker

The short-circuit characteristics of low-voltage circuit breakers are important performance and safety indicators of circuit breakers. When a short circuit accident occurs in the circuit, whether the circuit breaker can disconnect the circuit in time is an important guarantee for power safety. Therefore, when the circuit breaker is designed and applied in a complete set of equipment, the short circuit characteristics of the circuit breaker must be considered in combination with the actual situation. Safe operation provides protection so as to avoid unnecessary loss of property. The short-circuit characteristics that affect the circuit breaker are many, such as the installation method, GB 14048 provides that the circuit breaker is generally installed vertically, but in some special conditions, subject to space constraints, the ease of opening and closing conditions and other conditions, Horizontal mounting is required, so the short-circuit characteristics of the circuit breaker in this case may not be fully guaranteed. At high altitudes, it is also easy to affect the short-circuit characteristics of the circuit breaker. Because of the thin air in the plateau area, it will affect the arc extinguishing performance of the air dielectric quenching equipment, extend the arc extinguishing time of the circuit breaker, and severely burn out the contacts. Reduced on-off capacity. At the same time, the size of the space will also affect the short-circuit characteristics. In a complete set of equipment, when the circuit breaker is disconnected, there is a large amount of energy release, which will destroy the cabinet structure and cause damage to the equipment. Therefore, when product design under certain special working conditions is required, the degree of influence on the short circuit characteristics of the circuit breaker must be understood. If necessary, a short circuit characteristic test of the circuit breaker under special operating conditions is required to ensure the normal use of the device and avoid safety accidents. .


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