A wirewound resistor is a type of resistor that uses a conductive wire wrapped around an insulating core to resist the flow of current in a circuit.
This type of resistor is made by wrapping a wire around a core. The wire’s length and diameter control the resistance value, and the core size determines the range of possible resistance values. Wirewound resistors are used when either a larger amount of power is required to be dissipated or very high accuracy is required.
What Is the Technicality of a Wirewound Resistor?
Since wirewound resistors are made by winding a wire around an insulating core they inherently have more inductance than other types of resistors. The inductance of a wire can significantly impact how it behaves in high-frequency applications. This can be managed by using special wiring methods, which create a magnetic field that cancels out the inductance of the current in the wires. However, even wirewound resistors with a non-inductive wrapping pattern will have some parasitic inductance
They also utilize the resistance present in all conducting wires to their advantage. This resistance can be increased by making the wire longer and/or thinner. However, the power rating is also directly proportional to the wire thickness. If we want a resistor with high resistance and power or voltage rating, it will need to be longer. This, in turn, means that the resistor will be larger in size and cost more.
They have been used in industrial and high-power applications for many years and are known for their tolerance (0.005% is common) and long-term stability. They are also a good choice because they don’t have the internal stress issues that other resistors have. They are also stable over a long period of time, and they can have either a low-temperature coefficient or a very high-temperature coefficient depending on the wire alloy.
The Wirewound Resistor’s Inductance
The most common way of creating wirewound resistors involves the method of helical winding. Thus, it is made by wrapping a wire around a cylindrical core. The result is a resistor that looks like an inductor. The inductance is caused by the magnetic field that is produced by the current flowing through the coiled wire. The more coils there are in a component, the stronger the resulting magnetic field will be. Inductance is a measure of a coil’s opposition to changes in current and is thus increased when there are more coils. This will result in the effective resistance of the resistor changing as the frequency of the circuit changes.
By winding the resistor in a specific way, you can reduce the amount of inductance, but the added complexity will significantly increase the cost of the resistor.
A Wirewound versus a Film Resistor
Film resistors are generally made with a film of metal deposited on an insulating substrate. The metal film can be either thick or thin. The thicker the film, the greater the range of resistance values the resistor can have. Thin film is really only used for very high-precision applications. Thick film resistors are usually preferred because they have more power, and a greater range of resistance values than thin film. The metal film is usually deposited on a ceramic substrate, but other materials such as glass, mica, or paper can also be used.
Film resistors are cheaper, smaller, and work better at high frequencies than wirewound resistors. However, wirewound resistors are more robust and can handle far higher wattages.
Conclusion
A wirewound resistor is a type of resistor that uses a coiled wire to create resistance. This type of resistor is often used in high-power applications because it can handle a lot of current without overheating.
Wirewound resistors are also available in a variety of sizes and resistance values, making them a versatile option for many different applications.
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