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What Is Wirewound Resistor, Detailed Description Of wWirewound Resistor

What Is Wirewound Resistor, Detailed Description Of wWirewound Resistor

October 05 , 2023 0

Wirewound Resistors Introduction

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

Wirewound resistors are made of nickel-chrome wire or manganese-copper wire, con-copper wire wound on ceramic tubes, and are divided into two types: fixed and debuggable. Wirewound resistors are characterised by extremely high precision of resistance value, low noise, stability and reliability at work, can withstand high temperature, and can still work normally at an ambient temperature of 170°C. However, it is large in size and has a high resistance value. However, it is large and low resistance value, mostly below 100KΩ. In addition, due to structural reasons, its distribution capacitance and inductance coefficient are relatively large, and cannot be used in high frequency circuits. These resistors are usually used in high power circuits for voltage reduction or loads.

Types of Wirewound Resistors

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

Commonly used wirewound resistors are: RX20, RX21, RX22 glazed wirewound resistors, RX25 painted wirewound resistors, RX24 power wirewound resistors, RX10, RX12 precision wirewound resistors, RXG5 wirewound ceramic housed resistors and so on.

Because of their high precision and good stability, wirewound resistors can be used in instrumentation circuits, such as the voltage and current divider circuits of pointer multimeters, and also in resistance box circuits. And because of its ability to withstand greater power, also used in power supply circuits to do current limiting resistors, but because of its large inductance, it can not be used in high frequency circuits (interference with the circuit).

Principle of Wirewound Resistors

Wirewound resistor is a type of resistor with resistance wire wound on an insulating skeleton and then insulated and encapsulated, as shown in the figure, the resistance wire is generally made of alloys such as nickel-chromium and manganese-copper with a certain resistivity, and the insulating skeleton is generally made of ceramics, plastics, and metal skeleton coated with insulating layer. It is characterised by small temperature coefficient and high precision. In the wirewound resistors, there is a ceramic skeleton, in the outer layer of the resistor coated with glaze or other heat-resistant and good heat dissipation of the insulating material of the high-power wirewound resistors, wirewound resistors are characterised by high power dissipation, up to hundreds of watts, mainly used as a high-power loads, and can be operated in the temperature of the environment of 150 ℃ ~ 300 ℃.

In the wirewound resistor, there is a kind of adjustable wirewound resistor, which is equipped with a movable ring as the contact lead outside of the wirewound, leaving a narrow window on top of the glaze (lacquer) layer, exposing the wirewound contact channel, and the ring can be adjusted to the resistance value through the contact moving on the contact channel, so it is a kind of variable resistor. Commonly, there are two types of wirewound resistors: glazed wirewound resistors and lacquered wirewound resistors.

The Role of Wirewound Resistors

Wirewound resistors are constructed with resistance wires wound on an insulating skeleton, and are generally made of a medium with a certain resistivity, such as nickel-chromium, manganese-copper, and other alloys. Wirewound resistors are mainly used in low-frequency AC circuits to play the role of voltage reduction, shunt, load, feedback, trans-energy, matching, etc., or in power supply circuits to play the role of the absorber and voltage divider, but also used as a shunt in the shock circuit and transformer in the attenuation adjustment and pulse formation circuit. In addition, it can also be used for the discharge and spark elimination of filter level capacitors in rectifiers. Meanwhile, they can be widely used in home appliances, medical equipment, automotive industry, railway, aviation, military equipment and instruments.

Wirewound Resistors

The idea is roughly like this: wirewound resistor is a resistor wire wound in a certain direction on an insulated rod or insulated column, but this single spiral wirewound resistor will produce inductive effect when connected to the circuit, affecting the accuracy. In order to eliminate this effect, so the double helix reverse winding method, so that the inductance generated by the two coils offset each other, the entire wirewound resistor to the external circuit shows no inductance or micro-inductance, which is non-inductive wirewound resistors. The principle of operation is to allow two coils with opposite magnetic field directions to cancel each other's inductance, resulting in a non-inductive or micro-inductive characteristic to the external circuit.

How To See The Resistance And Power OF A Wirewound Resistor

Connect the resistor and the slide rheostat in series in the same circuit, measure the current I through the resistor with an ammeter, measure the voltage U across the resistor with a voltmeter, calculate the resistance value from R=U/I, and calculate the power from P=UI.

Application Areas OF Wirewound Resistors

Wirewound resistors and on-load voltage regulation refer to the transformer on-load tap-changer voltage regulation, the difference is that the non-excited voltage regulator does not have the ability to switch gears with the load, because this on-load tap-changer in the process of switching gears, there is a short-time disconnecting process, disconnecting the load current will result in the contacts between the pulling arc burns the on-load tap-changer or a short-circuit, so that when the gear adjustment must be made to make the transformer off the power supply. Therefore, the transformer must be de-energised during gearing. Therefore, it is generally used for transformers that do not require very strict voltage requirements and do not require frequent gearing. The on-load tap-changer can be switched with load, because the on-load tap-changer in the gearing process, there is no short-time disconnection process, after a transition resistance transition, from one gear to another gear, and thus there is no load current disconnection of the arc process.

Generally used for the voltage requirements of strict need to frequently adjust the gear transformer. Most substations are outdoor air-insulated substations, substations, all primary equipment in accordance with the requirements of the main junction of the connection of their own independent open layout, control and protection devices are arranged in the majority of the control room, so this substation occupies a large area of land, poor environmental effects, low reliability, high operating and maintenance costs. Gas-insulated metal-enclosed substations, i.e. GIS substations, are highly reliable and have a long service life compared with outdoor air-insulated substations, but their primary investment costs are high. A new type of substation, the modern compact substation, is being researched and developed, combining the advantages of these two types of substations. In the following, we will discuss the modern compact substation and its primary and secondary equipment integration technology based on modern microcomputer, optoelectronic, and communication technologies from the perspective of technical and economic optimisation, and analyse the technical and economic benefits generated by this substation.

Advantages And Disadvantages OF Wirewound Resistors

Many resistance engineers like to use wirewound resistors, in fact, it is wirewound resistors in the AC and DC circuits for voltage divider, buck, shunt and load, etc., engineers can make good use of these characteristics of wirewound resistors should be in the circuit of precision instrumentation, telecommunication instruments, electronic equipment. So wirewound resistors are used so much, what are its advantages and disadvantages?

First of all, we analyse the advantages of wirewound resistors, we know that the reason why wirewound resistors are widely used this is also due to the resistance value of the watt-wound resistor is extremely high precision, work with low noise, stable and reliable, temperature coefficient is small, able to withstand high temperatures, in the ambient temperature of 170 ° C can still work properly.

Although wirewound resistors have so many advantages, but there are also disadvantages, such as large size, low resistance value, and due to structural reasons, and wirewound resistors can not be used in high-frequency circuits.