The function principle and structure selection of drop-out fuse

The role of drop-out fuse

The 10kV specification equipment can be installed on the high-voltage side of the transformer on the pole, where the transformer and capacitor are connected to the line, and the drop-out fuse effectively plays the role of overload protection and short-circuit protection in the circuit. At the same time, it can also be installed at the end of a long line or on a branch line. This approach can extend the protection of the range that the relay protection cannot. The structure of the drop-out fuse is not complicated but relatively simple, and it is also very economical in terms of price, and it does not require a lot of effort in future maintenance, because the small size is conducive to installation work. The fuse is in the distribution network. Has been widely used.

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Working principle of drop fuse

The fuse passes through the fuse tube and both ends are tightened at the same time. When the fuse is in a normal working state, the fuse depends on the tension of the fuse to make the upper movable contact and the lower static contact of the fuse tube form reliable contact. If the line fails, the drop-out fuse will immediately blow the fuse, thereby forming an arc and generating a large amount of gas in the fuse tube. The arc is blown to lengthen the arc to extinguish it, and then it will be extinguished. It will lose the pulling force of the fuse and under the action of gravity, the fuse tube will fall to cut off the circuit according to the principle of inertia to form an obvious disconnection distance.

Structural composition of drop-out fuse

The overall structure of the equipment is assembled from upper and lower conductive parts, fuse tubes, insulating parts and fixed parts. The fuse tube structure includes fuse tubes, fuses, caps, operating rings, upper and lower moving and static contacts, short shafts, etc. The composition of parts and components is shown in the figure below.

Transmitter|Encoder|Soft starter|Power supply|VFD|Light curtain|Servo products|Human-machine interface|Solenoid valve|Cylinder|Actuator|Flow meter|Transformer|Thyristor|Sensor|Deceleration drive gearbox reducer|Linear guide|Circuit breaker|Refrigeration compressorAll industrial products of okplazas are purchased from the original factory or formal channels of agents to ensure the original authenticity, which perfectly solves the problem of industrial product sample procurement and small-batch procurement for the majority of engineers and purchasing personnel.

Usually, the fuse selection of drop-out fuse is generally made of copper-silver alloy, which has the characteristics of relatively high melting point and certain mechanical strength. A release pressure cap is also installed on the upper end of the fuse tube, which is mainly used to place a low melting point fuse. When the fuse breaks a large current, the thin fuse of the upper end cap will melt to form a double-ended exhaust. When the device breaks a small current, the thin fuse on its upper end cap will not act, thus forming a single-ended exhaust.

Selection method of drop-out fuse

Generally, the drop-out fuse of 10kV specification is suitable for outdoor places where there is no conductive dust, corrosive gas, flammable and explosive in the surrounding air, and the temperature difference ratio within a year must be within ±40℃. When selecting the drop-out fuse, it is mainly considered in accordance with the two technical parameters of rated voltage and rated current. That is to say, the rated voltage of the equipment must be mutually related to the rated voltage of the protected equipment (line). match.

Furthermore, when choosing a drop-out fuse, its rated current should be greater than or equal to the rated current of the melt. Generally, the rated current of the melt can be selected to be about 0.3 to 0.1 times that of the fuse. Moreover, if the rated current of the fuse link is selected at 100kVA and below, take about 2 to 3 times, if it is above 100kVA, then it should be about 1.5 to 2 times. In addition, the three-phase short-circuit capacity of the protected system must be considered, and the selected drop-out fuse must be checked to ensure that the three-phase fuse capacity of the protected system is less than the upper limit of the rated breaking capacity of the equipment. It is also greater than the lower limit of the rated breaking capacity.

The above is the function principle and structure selection of the drop-out fuse, I hope to help everyone.You can also log in to the okplazas.com motor mall to check the fuse-related product information, welcome to email: [email protected] for consultation, and you can also contact WeChat customer service +86-13689242098 online for product consultation!