As an indispensable safety material in the electric power industry, circuit breakers are products that prevent further safety risks, but after the use, the circuit breaker terminals will heat up, then what factors affect it? The editor will introduce you.
First, the indirect cause of the heating of the circuit breaker terminal
The circuit breaker terminal and the contact system inside the circuit breaker, the thermal release, and the electromagnetic release are connected through the main circuit. The heat of the three is transmitted to the terminal through the internal metal conductor, so the contact system must be The heat of the thermal trip unit and the electromagnetic trip unit are separately analyzed. The contact system includes a moving contact and a static contact. When the two contacts, a path is formed. When the two are separated, the circuit is disconnected. The circuit breaker is closed and the circuit is closed. The heat generation and the principle of direct heating of the terminal are realized. The exact same factors, including current and contact resistance. The core component of the hot bimetal release is a bimetal. When the line is overloaded, it relies on its characteristic of heat and bending to open the circuit. Therefore, it has the characteristics of being easy to generate heat. Some types of circuit breakers also need to wind the heating wire on the bimetal. To strengthen fever. The electromagnetic trip unit is composed of a yoke and an armature, and a current flows through the coil to form an electromagnetic field, which not only has resistance loss of the coil but also eddy current loss. The three are the main heat source inside the circuit breaker, and are connected to the terminal through the main circuit. Therefore, the heat generated by the circuit breaker terminal is not only affected by the resistance of the conductor at the terminal and the heating of the contact resistance, but also by the internal heating element of the circuit breaker. influences.
The above direct and indirect reasons, in the end which impact is greater. According to different situations to analyze. Under normal circumstances, when the contact resistance is within the normal range, the magnitude of the current is the main influencing factor. Under abnormal conditions, if the contact at the terminal of the circuit breaker is not good and the crimping is not strong, resulting in an increase in contact resistance, the influence of the contact resistance heat will be greatly increased.
It can be seen from the above analysis that the heat generation of the circuit breaker terminal is much more complicated than the heat generation of the terminal which is only used for connection. For actual electrical fire detection, the temperature characteristics of the circuit breaker terminals are worth studying. After all, there are more than one factor affecting the temperature of the circuit breaker terminals. Therefore, it is necessary not only to theoretically analyze the influencing factors of the heating, but also to conduct actual testing of the terminal temperature and analyze the specific data.
Second, the factors affecting the heating of the circuit breaker terminal
The mechanism of heat generation of the circuit breaker terminal is analyzed. The starting point is the circuit breaker itself. The heat source other than the circuit breaker is not considered. The circuit breakers in the actual distribution box are arranged side by side, so the heat, heat and heat are analyzed. The factors affecting the heating of the circuit breaker terminal include the following:
(1) Current size
From the thermal effect of the current analysis, the magnitude of the current is the most important factor. After all, the square of the current is involved in the calculation of the thermal effect.
(2) Contact resistance
From the thermal effect of the current, the contact resistance is the most important factor influencing the current.
(3) Internal heat source
The effect of the internal heat source on the heating of the circuit breaker terminal is reflected by heat transfer. The heat transfer efficiency of the metal conductor must be considered.
(4) External heat source
The external heat source is the nearby circuit breaker. They have two effects on the heat generation of the circuit breaker terminal. One is heat transfer and the other is heat dissipation. If the circuit breaker next to the load rate is high and the heat is obvious, it will affect the nearby circuit breaker through heat transfer, and the heat dissipation of the circuit breaker itself will be affected by the presence of the circuit breaker next to it.
(5) Internal heat dissipation space
The heat dissipation space inside the circuit breaker also has a certain influence on the heat generation of the circuit breaker terminal. It is mainly reflected in the form of heat dissipation. The smaller the internal heat dissipation space, the more likely the heat is accumulated, and the heat accumulation causes the temperature to rise.
(6) Cross-sectional area and material of the wire
The cross-sectional area and material of the crimping wire of the terminal block are the determining factors of the conductor resistance per unit length, which can be included in the range of current thermal effect, and affect the temperature of the terminal itself through heat transfer.
(7) tightening torque
Tightening torque refers to the torque when fixing the terminal block of the circuit breaker. The magnitude of the tightening torque directly affects the contact resistance. Because the contact resistance has many influencing factors, and most of them are difficult to judge easily, only the tightening torque is more intuitive, so it is used as a separate one. Influencing factors.
If the circuit breaker terminals are hot, it may not be ideal for their safety and security, and even cause additional hidden dangers, resulting in problems and troubles in current leakage. Therefore, we should choose to understand similar to the above. The reason why the circuit breaker terminal block is heated, if there is similar performance, it should be analyzed in time and the fault is eliminated, and reasonable and reliable solutions and suggestions should be selected to start the maintenance and repair process, so that the circuit breaker itself can be used as much as possible. Maximize the value and avoid extra losses and troubles.