General-Purpose Failsafe Moulded Wirewound Resistors Welwyn Components SP20/SP20F Series • Drop-in replacement for BW20/BW20F • Predictable fusing characteristics • 1 watt rated with 1/2 watt dimensions • 0.1 ohm to 1200 ohms • Weldable and solderable magnetic leads Electrical Data Type SP20 SP20F EIA RS-344 Style CRU 1 MIL-R-11 Style RC20/RC32 Resistance Range ohms Tolerance 0R1 to 1k2 0R1 to 1k % Power rating ±5, ±10 watts 1 at 50°C 1 at 50°C 0.75 at 70°C 0.75 at 70°C 0.5 at 100°C - Derating to 0 at 160°C Derating to 0 at 160°C √PR Maximum continuous working voltage Minimum insulation resistance dry 10,000 Meg wet 100 Meg Minimum dielectric withstanding volts ATM 700V Reduced pressure RMS 450V Hotspot temperature rise 120°C at 1 watt Current noise Negligible Physical Data Dimensions (mm) Type L D d f SP20 9.91±0.25 3.56±0.20 0.813±0.05 38.1±3.2 SP20F 9.91±0.25 3.56±0.20 0.813±0.05 38.1±3.2 d D L f Resistive Element Encapsulation All resistor types have resistance alloy winding on a braided fibreglass substrate. Intermediate silicone coatings are used to enhance processibility and to provide protection to the resistive element. The SP20 and SP20F are encapsulated utilizing a compression molded phenolic plastic material. The SP20F has a flame resistance coating applied over the resistive element to provide flammmability protection when destructive overloads may occur. Termination The SP20 and SP20F resistors are terminated using an alloy coated copper flashed steel lead welded to a cap of the same material. This termination assembly is mechanically crimped, utilizing an improved crimp design, to the resistive element. Marking All products are marked utilizing heat and solvent resistant colour code bands consistent with EIA/MIL requirements. The first band is double width to designate wirewound construction. A fifth band, blue in colour, is used for flameproof identification. General Note Welwyn Components reserves the right to make changes in product specification without notice or liability. All information is subject to Welwyn’s own data and is considered accurate at time of going to print. A subsidiary of TT electronics plc © Welwyn Components Limited · Bedlington, Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: [email protected] · Website: www.welwyn-tt.com Issue B · 03.02 95 General-Purpose Failsafe Moulded Wirewound Resistors Welwyn Components SP20/SP20F Series Performance Data Test Temperature coefficient (ppm) ppm/°C SP20 SP20F <1R ±800 <1R ±800* ≥1R ±150 Dielectric withstanding voltage RMS Momentary overload ≥1R ±150 700V % 5 Low temperature operation % 5 Temperature cycle % 5 Humidity % 5 Load life % 5 Terminal strength % 5 Resistance to solder heat % 5 *0.1 ohm SP20F <1000 ppm. SP20 Power Derating SP20F Power Derating 2.5 Power (watts) Power (watts) 2.0 1.5 1.0 0.5 0 Ambient Temperature (°C) 50 100 150 Ambient Temperature (°C) 200 SP20 and SP20F Temperature Rise 0.1 ohm 1 ohm 10 ohm 100 ohm 1000 ohm Time (seconds) Temp (°C) Power (watts) SP20F Typical Fusing 0 Power Input (watts) Packaging Resistors are supplied tape and reel. 4,000 pcs per reel. © Welwyn Components Limited Bedlington, Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: [email protected] · Website: www.welwyn-tt.com 96 Issue B · 03.02