Introduction to High Power Wirewound Resistors

Wirewound resistors are made of constantan wire or manganese copper wire wound on an insulating skeleton. It has many advantages: high temperature resistance, high precision and high power. But its frequency modulation characteristics are poor, which is mainly due to its large distributed inductance. It is widely used in low frequency precision instruments.

Wire-wound resistors are made of nickel-chromium wire, manganese copper wire, and constantan wire wound on a porcelain tube. There are two types: fixed and adjustable. Wirewound resistors are characterized by extremely high resistance value accuracy, low noise, stable and reliable operation, can withstand high temperatures, and can still work normally at an ambient temperature of 170°C. But it is large in size and low in resistance, mostly below 100KΩ. In addition, due to structural reasons, its distributed capacitance and inductance are relatively large, so it cannot be used in high-frequency circuits. This type of resistor is usually used as a step-down or load in high-power circuits.

Types of Wirewound Resistors

There are many types of wirewound resistors, which can be generally divided into two types: fixed type and adjustable type.

Commonly used wirewound resistors are: RX20 type, RX21 type, RX22 type enameled wirewound resistors, RX25 type painted wirewound resistors, RX24 type power type wirewound resistors, RX10, RX12 type precision wirewound resistors , RXG5-type wire-wound ceramic shell resistors, etc.

Because wirewound resistors have the characteristics of high precision and good stability, they can be used in circuits of instruments and meters, such as voltage divider and current shunt circuits of pointer multimeters, and can also be used in resistance box circuits. And because it can withstand large power, it is also used as a current limiting resistor in the power supply circuit, but because of its large inductance, it cannot be used in high-frequency circuits (interference with the circuit).

How Wirewound Resistors Work

Wirewound resistors are a type of resistors that are wound on an insulating skeleton with a resistance wire and then processed by insulating packaging. As shown in the figure, the resistance wire is generally made of nickel-chromium, manganese-copper and other alloys with a certain resistivity. The skeleton is generally made of ceramics, plastics, and metal skeletons coated with insulating layers. It has the characteristics of small temperature coefficient and high precision. Among the wirewound resistors, there is a high-power wirewound resistor that uses ceramic as the skeleton, and the outer layer of the resistor is coated with glaze or other heat-resistant and heat-dissipating insulating materials. Wirewound resistors are characterized by large power dissipation. , up to hundreds of watts, mainly used as high-power load, can work in the environment of 150 ℃ ~ 300 ℃ temperature.

Among the wirewound resistors, there is also an adjustable wirewound resistor, which is equipped with a movable snap ring on the outside of the wirewound as a contact terminal, and a long and narrow window is left on the glaze (paint) layer to expose the wirewound. The contact track, the snap ring can adjust the resistance value by moving the contact on the contact track, so it is a variable resistor. There are two common types of glazed wirewound resistors and painted wirewound resistors.

Source sharing: Shenzhen Jiajie Weiye Technology Co., Ltd.

Contact: Miss Zhang/Mr. Zhang; Tel: 0755-82731845/18165782726

QQ: 1456723845, 2511758816