250 Series Thin Stackohm Vitreous Enamel Power FeatureS When limited space is a consideration, choose Ohmites thin stackable 250 Type resistors. These Small size-to-power ratio. oval-shaped ceramic-core resistors feature a low Stackable profile to permit installation in spaces with height In te gra l mo unt in g br ac ke t c ond uct s he at to restrictions. They are also equipped with integral mounting sur face. mounting brackets so they can be fastened to a chassis and stacked in locations with limited sur face Low profile for use in equipment where space is area. limited. When properly fastened, the mounting brackets All-welded construction. add a heat sinking benefit resulting in a smaller size RoHS compliant product available. Add E suffix to per watt. Durable 250 Type resistors are fully welded part number to specify. and coated with lead free vitreous enamel. SerieS SPeciFicatiONS Series Wattage Ohms Max. Voltage* F10 10 1.0-15K 187 F20 20 1.0-50K 815 F30 30 1.0-10K 281 F40 40 1.0-25K 655 F55 55 1.0-30K 1405 Adjustable versions and other sizes available Consult Ohmite Also available in low cost Centohm or Silicone coating Consult Ohmite. * Maximum Voltage is based on Ohms Law V=P*R as limited by the resis- tance value of specified product characteriSticS Lead free vitreous enamel Coating Core Ceramic Terminals Tinned lug with hole. RoHS solder composition is 96% Sn, 3.5% Ag, 0.5% Cu Derating Linearly from 100% +25C to 0% +350C Tolerance 5% (J) Power rating Based on mounting a single resistor on a metal surface measuring 10 (254mm) square by 0.04 (1.016mm) thick. Reduce rating by 15% when mounting on non-metallic surface Overload 10x rated wattage for 5 seconds if max. voltage is not exceeded 1 to 20: 400 ppm/C Temperature coefficient Over 20: 260 ppm/C 500 VAC: 10 and 20 watt rating. 1000 VAC: 30, 40 and 55 watt rating (mea- Dielectric with- sured from lug to mounting bracket) standing voltage Max. amps To calculate, use the formula P/R 110 1-866-9-OHMITE Intl 1-847-258-0300 Fax 1-847-574-7522 www.ohmite.com info ohmite.com250 Series Thin Stackohm Vitreous Enamel Power dimeNSiONS (in. / mm) 0.125 0.625 3.175 mm Series Wattage Length L Length A 15.875 mm 0.031 Diam. F10 10 0.750 / 19.050 1.000 / 25.400 0.794 mm 0.063 1.588 mm F20 20 2.000 / 50.800 2.313 / 58.750 Diam. F30 30 1.250 / 31.750 2.000 / 50.800 10W & 20W 0.125 F40 40 2.000 / 50.800 2.750 / 69.850 3.175 mm L F55 55 3.500 / 88.900 4.250 / 107.950 0.110 : A 0.125 * 2.776 mm *Reference dimension only varies according to resistance 3.175 mm value. 0.375 Note: When resistors are stacked, use washers or spacers 0.250 as required to insure clearance and improve power dissipa- 9.525 mm 6.350 mm tion. 0.188 4.763 mm 0.125 Diam. 3.175 mm 0.109 2.776 mm Diam. 30W, 40W & 55W 0.196 4.979 mm L 0.250 A 6.350 mm 0.250 * 6.350 mm 0.125 3.175 mm 0.438 11.113 mm mOuNtiNg Derating for stacked mounting In addition to the standard box bracket, stud type brackets are available for stacking the standard size resistors. Stud Stacked resistors should be derated to prevent excessive tem- peratures due to proximity. Approximate ratings are given in type brackets are available in two heights: standard (SS, 0.437/11.113mm) and high (SSH, 0.531/13.494mm). The the table. Percent of Single Unit Rating SSH stud is recommended when stacking the adjustable Type Miniature with 260, as it assures clearance for the adjustable lugs to pass No. of 0.094 (2.381 mm) eachother. Spacer washer No. 6027 (O.D. 0.219/5.556mm, Std. or Inter. Resistors Miniature Spacer Washer I.D. 0.125/3.175mm, thickness 0.094/2.381mm) is recom- 2 70 70 75 mended for use with the miniature adjustable and fixed resis- 3 60 60 69 tors to provide clearance, as explained above, or increased 4 50 50 60 wattage. See chart. 0.125 0.125 0.625 0.188 3.175 mm 3.175 mm 15.875 mm 4.763 mm 0.031 Diam. 0.094 Diam. 0.125 Diam. 0.794 mm 0.063 2.381 mm 0.063 3.175 mm 0.109 1.588 mm 1.588 mm 2.776 mm B B B Diam. Diam. Diam. 0.813 W W 0.125 0.196 0.196 20.638 mm 3.175 mm 4.979 mm 4.979 mm L L L 0.250 0.110 : 0.188 Core Core Core A A A 2.776 mm T 4.763 mm T 6.350 mm T size size size 0.125 0.125 0.375 0.438 0.250 3.175 mm 3.175 mm 0.438 9.525 mm 11.113 mm 6.350 mm 11.113 mm 0.188 0.188 Brackets 4.763 mm 4.763 mm cemented 0.125 Diam. 0.125 Diam. in core 3.175 mm 0.109 3.175 mm 0.109 2.776 mm 2.776 mm B B 0.156 x0.313 Diam. W W 3.969 x 7.938 mm 0.196 Slot 4.979 mm L L 0.250 0.188 Core Core A A 6.350 mm T 4.763 mm T size size 0.125 0.438 0.531 0.5 3.175 mm 11.113 mm 13.494 mm 12.7 mm (SS) (SSH) (continued) 1-866-9-OHMITE Intl 1-847-258-0300 Fax 1-847-574-7522 www.ohmite.com info ohmite.com 111 0.938 0.375 23.813 mm 9.525 mm 1.000 0.375 25.400 mm 9.525 mm
