Bare Wire Resistors: What They Are and Why Fairfild Solutions Stand Out

Bare wire resistors are devices designed to offer high thermal dissipation capability while maintaining extremely low thermal resistance. Thanks to their exposed wire-wound structure, these resistors allow efficient heat exchange with the surrounding environment and can be easily ventilated or assembled in groups to safely and reliably manage high power levels. They are widely used in industrial automation, energy systems, railway applications and in all environments that require robust braking, load or grounding solutions.

Fairfild offers two main families of bare wire resistors – RMS and RDP – both engineered to deliver excellent reliability, wide dissipation capability and strong design flexibility.

RMS Bare Wire Resistors

The RMS series consists of wire-wound resistors mounted on ceramic supports and fixed to a metal frame. This configuration allows direct heat dissipation from the wire, resulting in very low thermal resistance and high thermal capacity. The variant with mica bar provides even higher insulation values and reduced weight, making integration easier and more efficient.

RMS bare wire resistors are commonly used for dynamic braking, neutral grounding, motor starting, RC circuits for capacitor charging and discharging, and as core elements for resistive loads. The family includes six models with nominal power ratings from 0.9 kW to 3.6 kW and ohmic values ranging from 1 Ω to 110 Ω. Insulation ratings are 1000 V or 3000 V for the mica-bar version.

RMS resistors can be mounted in groups using tie rods and ceramic spacers. Their open structure makes them ideal for natural or forced ventilation. Stainless steel terminals ensure reliable connections via cable lugs. For correct installation, a minimum spacing of 30 mm between resistors is recommended.

RDP Bare Wire Resistors

The RDP series follows the same construction philosophy: wire wound on ceramic supports mounted on a metal frame, ensuring high dissipation capability and excellent thermal efficiency. Its distinctive rhomboidal shape further improves ventilation, making these resistors especially suitable for high-power applications.

RDP bare wire resistors are used in dynamic braking systems, resistive loads and in RC circuits involving capacitor charge and discharge. The range includes seven models with power ratings from 1200 W to 6500 W and ohmic values from 1.8 Ω to 300 Ω. The maximum operating voltage is 2000 V.

These resistors can also be assembled in groups using tie rods, ceramic spacers or support bars, always maintaining a minimum spacing of 30 mm to promote proper cooling.

Fairfild Bare Wire Resistors

Fairfild designs and manufactures both standard and custom bare wire resistors, offering high-performance solutions for all types of industrial applications. The RMS and RDP families ensure optimal dissipation, long-term durability and maximum operational safety even in demanding environments.

For more detailed technical information, you can consult the dedicated RMS and RDP datasheets or contact us for a personalized consultation. The Fairfild team supports each designer in selecting the most suitable bare wire resistor, with ready-to-use configurations or fully customized solutions.