What Is a Wirewound Resistor?
A wirewound resistor is a resistor made by winding a resistive metal wire around an insulating core, able to carry high power.
Its Structure
A resistive wire such as nichrome is wound onto a ceramic core and usually protected with a heat-resistant coating. The wire's length and thickness set the resistance.
Advantages
| Advantage | Explanation |
|---|---|
| High power | Dissipates watts of power as heat |
| Precision | Tight tolerance possible |
| Stability | Changes little with temperature |
Disadvantage: Inductance
Because the wire is coiled, it forms an inductance like a coil; so at high frequency it behaves undesirably (non-inductive types exist).
Where Is It Used?
As a power resistor in braking, load dumping, current limiting and precision high-power applications.
Non-Inductive Types
To solve the inductance problem the coiled structure creates, non-inductive wirewound resistors are made with special winding techniques. These suit applications that need both high power and high-frequency operation.
Common Mistakes
- Using it at high frequency: the inductance corrupts the signal; choose a non-inductive type if needed.
- Skipping cooling: it heats up significantly at high power; airflow/heat sink may be needed.
- Mounting on a flammable surface: the body gets very hot.
Frequently Asked Questions
Why does it get so hot?+
Why isn't it suitable at high frequency?+
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