RW Series Axial Wire Wound Resistors

What are the RW Series Axial Wire Wound Resistors?

The RW is a general-purpose axial leaded wire wound resistor designed to deliver reliable, stable power dissipation across a wide range of industrial, commercial and consumer electronics applications. Its construction follows the established wire wound principle: a length of precision resistance wire — typically a nickel-chromium or copper-nickel alloy selected for consistent resistivity and controlled temperature coefficient — is wound in a single layer around a ceramic core. Metal caps are pressed over the ends of the core and the wire terminations are welded to the caps, producing a completely welded internal assembly that eliminates the failure modes associated with crimped or press-fit connections.

The wound assembly is encapsulated in multiple layers of silicone coating. Silicone offers considerably higher temperature tolerance than conventional epoxy or lacquer coatings, allowing the RW to operate reliably across an ambient temperature range of −55°C to +200°C without degradation of the coating or the underlying resistive element. The coating is non-flammable and resistant to common cleaning solvents, making it well suited to both wave-soldering environments and in-service conditions where chemical exposure may occur. Its mechanical flexibility also allows the coating to accommodate differential thermal expansion between the wire, core and caps over repeated thermal cycling without cracking.

The RW series covers power ratings of 0.5W, 1W, 2W, 3W, 5W, 7W and 10W, with a resistance range of 0.1Ω to 100kΩ using E24 preferred values. Tolerance grades of ±1%, ±2%, ±3%, ±5% and ±10% are available across the range, making the series suitable for applications requiring either close-tolerance accuracy or cost-efficient general-purpose resistance. The temperature coefficient of resistance is 260ppm/°C maximum, consistent with the nickel-chromium winding wire used in standard wire wound construction. Maximum working voltage is defined by the square root of the product of rated power and resistance value, ensuring the applied voltage remains within the dielectric capability of the coating. Dielectric withstanding voltage is AC 500V for one minute.

Short-time overload capability is rated at five times the nominal power for five seconds for variants up to 3W, and ten times the nominal power for five seconds for variants above 3W, with a resistance change limit of ±2.0% in both cases. Long-term load life testing confirms resistance stability of ±2.0% after 1,000 hours under rated power at 70°C on a 1.5-hour on, 0.5-hour off cycle. Resistance values up to 5W are identified by a four-band colour code with an additional black band denoting the wire wound construction type; variants above 5W carry a printed resistance marking. The RW is supplied in standard axial taped packaging to support automated through-hole insertion, and is also available in bulk format.

Model: RW
Resistor type: Wire wound
Description: Wire wound
Power Rating: 0.5W~10W
Resistance (Ω): 0.1~680
Tolerance (%): ±1, ±2, ±3, ±5, ±10
TCR (ppm/C): 260 max.

Model: SMW
Resistor type: Wire wound
Description: Power chip
Power Rating: 2W, 3W, 5W
Resistance (Ω): 0.1~680
Tolerance (%): ±1, ±2, ±3, ±5, ±10
TCR (ppm/C): 200

Model: FWR
Resistor type: Wire wound
Description: Fusible
Power Rating: 1W, 2W, 3W, 5W
Resistance (Ω): 0.1~200
Tolerance (%): ±5
TCR (ppm/C): 300

Model: RQA
Resistor type: Wire wound
Description: Ceramic encased
Power Rating: 5W~20W
Resistance (Ω): 0.1~100k
Tolerance (%): ±5, ±10
TCR (ppm/C): 260, 400

Model: PWR
Resistor type: Wire wound
Description: Precision wire wound
Power Rating: 0.5W~10W
Resistance (Ω): 0.1~100k
Tolerance (%): ±0.1, ±0.25, ±0.5, ±1, ±2
TCR (ppm/C): 20, 50, 90