The fuse resistor has the function of ordinary resistance under normal conditions. Once the circuit fails and exceeds its rated power, it will disconnect the circuit within a specified time, thereby achieving the role of protecting other components. Insurance resistors are divided into two types: irreparable type and repairable type. Next, Wanliansheng Technology will talk about the characteristics of insurance resistors and the difference from ordinary resistors.

Features

It plays a dual role of fuse and resistance in the circuit diagram, and is mainly used in the output circuit of the power supply circuit and the output circuit of the secondary power supply. They are generally low resistance (several ohms to tens of ohms) and low power (1/8~1W). Their function is to fuse in time when overcurrent to protect other components in the circuit from damage.

When the circuit load has a short-circuit fault and an overcurrent occurs, the temperature of the fuse resistor will rise to 500~600℃ in a short time. At this time, the resistive layer will be heated and peeled off and blown, which plays a role of insurance to improve The purpose of the security of the whole machine.

Judgment method

Although insurance resistors are widely used in power circuits, the marking methods in circuit diagrams of various countries and manufacturers are different. Although the labeling symbols are not yet unified, they have common characteristics:

(1) They are markedly different from general resistance, which is easy to judge in the circuit diagram.

(2) It is generally used in low-voltage or high-voltage circuits with large current capacity of power supply circuits or secondary power supply.

(3) There is only one color ring on the fuse resistor. As shown in the figure, the color of the color circle indicates the resistance value.

(4) In the circuit, the fuse resistor is welded on the circuit board with long legs (generally the resistor is welded close to the circuit board), and the distance from the circuit board is relatively long, which is convenient for heat dissipation and distinction.

Specifications

(1) RN1/4W, 10Ω fuse resistor, color ring is black, power is 1/4W; when 8.5V DC voltage is applied to both ends of the fuse resistor, the resistance will increase to more than 50 times the initial value within 60 seconds.

(2) RN1/4W, 2.2Ω insurance resistor, color ring is red, power is 1/4W; when 3.5A current passes, the resistance increases to more than 50 times the initial value within 2 seconds.

(3) RN1/4W, 1Ω insurance resistor, the color ring is white, and the power is 1/4W; when 2.8A AC current passes through, the resistance increases to more than 400 times the initial value within 10 seconds.

How to distinguish between ordinary resistance and insurance resistance

Both have the function of resistance, but the resistance fuse is equal to the resistance plus the fuse. When the added power exceeds the power of the resistance, the fuse will blow, and the entire resistance will not burn and smoke. The resistance is when the applied power exceeds its own power, it will burn up and smoke.