What Is a Power Resistor?
A power resistor is a resistor that can dissipate far more power as heat than ordinary resistors. It's used in high-power jobs such as load dumping, current limiting and braking.
Why Does the Power Rating (W) Matter?
The power a resistor dissipates is found with P = I² × R and turns into heat. A power resistor is designed to carry this heat safely.
Types
| Type | Feature |
|---|---|
| Wirewound | Precise, very high power |
| Thick film (power) | Compact, medium power |
| Cement (ceramic) | Cheap, durable, common |
Cooling
It heats up significantly at high power; body design, airflow and, if needed, mounting to a heat sink manage the heat.
Where Is It Used?
Power supplies, motor braking, load dumping (dummy load) and high-current current limiting.
Dummy Load
A common use of power resistors is to create an artificial load when testing a power supply or battery. A resistor of known value draws a certain current from the source, so the source's voltage and heating behavior under load can be measured safely.
Common Mistakes
- Leaving no power margin: pick a resistor rated at least 2× the calculated power.
- Ignoring cooling: as temperature rises the power-handling drops (derating).
- Placing it on a flammable surface: since it gets very hot, the mounting location matters.
Frequently Asked Questions
How many watts should a power resistor be?+
What is a cement resistor?+
Search parts related to "What Is a Power Resistor?"
Find the right part by comparing price, stock and distributors.