How to find the right Industrial Electrical Resistors AI guide
Written by an AI model from its trained knowledge.
What the AI looks for in Industrial Electrical Resistors
- Power rating and derating
- Calculate dissipation (P = I²R or V²/R) and choose a part rated for at least twice that, then check the derating curve for your ambient temperature. Ratings assume 25°C ambient and free air. Running near full rating cuts lifespan and makes the part hot enough to damage nearby components.
- Heatsink-dependent ratings
- For aluminum-housed and TO-package resistors, the headline wattage assumes a specified heatsink. Without one, expect a fraction of that rating; check the datasheet's free-air figure. This is the most common reason chassis-mount resistors overheat in service.
- Construction type
- Use metal film for precision and low noise, wirewound or ceramic-housed parts for high power, and thick-film or non-inductive types for pulse, RF or high-frequency switching. Standard wirewound parts are inductive and misbehave in fast circuits. Carbon composition parts drift but handle surges well.
- Tolerance and temperature coefficient
- Use 1% or better with a low ppm/°C rating for measurement, current sense and feedback dividers. 5% is fine for pull-ups, bleeders and load banks. Drift with temperature often matters more than the initial tolerance in sensing circuits.
- Voltage rating
- Check that the maximum working voltage exceeds the voltage across the part, separately from the power limit. This matters most for high-value resistors in mains or high-voltage dividers. High-value resistors can arc or break down before they reach their power limit.
- Current-sense specifics
- For shunts, use a 4-terminal (Kelvin) connection and low-TCR alloy elements such as manganin when values are in the milliohm range. Lead and solder resistance otherwise swamp the reading.
Brands that matter
- Vishay (Dale): Broad industrial range, including aluminum-housed, wirewound, metal film and precision parts.
- Ohmite: Specialist in high-power, wirewound, thick-film and non-inductive resistors.
- TE Connectivity (CGS): Widely used aluminum-housed and power resistors.
- Arcol: Well-known aluminum-clad power resistors for braking and load applications.
- Bourns: Current-sense and general-purpose resistors with clear datasheets.
- KOA Speer: Reliable metal film, metal oxide and current-sense resistors.
- Yageo: High-volume general-purpose resistors, including kits.
- Riedon: Precision, power and current-shunt resistors.
What to avoid
- Unbranded aluminum-housed resistors with no datasheet and an inflated wattage
- Running any resistor at its full rated wattage continuously, especially in an enclosure
- Standard wirewound resistors in high-frequency, pulse or snubber circuits
- Choosing on resistance alone without checking the voltage rating for high-voltage dividers
- Two-terminal low-ohm resistors where accurate current measurement is needed
Questions
Why does my 100 W aluminum resistor get too hot at 30 W?
The 100 W rating assumes it is bolted to a specified heatsink with thermal compound. Its free-air rating is much lower, so mount it on adequate metal or choose a larger part.
Can I combine resistors to get a higher power rating?
Yes. Identical resistors in series or parallel share power equally. Still derate each one, and keep them spaced apart so they don't heat each other.