33 3 RPS 250 www.vishay.com Vishay Sfernice Power Resistor for Mounting onto a Heatsink Thick Film Technology FEATURES Compliant with requirement 26 of NF-EN45545-2 High power rating: 250 W High overload capability up to 4 times nominal power (see energy curve) Easy mounting Low thermal radiation of the case Material categorization: for definitions of compliance DESIGN SUPPORT TOOLS AVAILABLE please see www.vishay.com/doc 99912 3D Models Developed for specific applications such as railroad electrical traction, this series can bear short overloads as high as fifteen times the nominal power. Designed to be mounted onto a heatsink, these power resistors exhibit remarkable characteristics. DIMENSIONS in millimeters 73 73 RPS 250D ZA3 RPS 250A ZA3 56 56 26 1 28 1 57 16.2 18.7 57 34 7.2 7.2 4.2 4.2 2 x M4 2 x M4 USEFUL DEPTH: 6 USEFUL DEPTH: 6 Note Tolerance unless stated: 0.2 mm STANDARD ELECTRICAL SPECIFICATIONS RESISTANCE RATED POWER LIMITING ELEMENT TEMPERATURE TOLERANCE MODEL SIZE RANGE P VOLTAGE U COEFFICIENT 25 C L % W V ppm/C (1) RPS 250 250 0.24 to 1M 250 5000 1, 2, 5, 10 150 Note (1) E24 series MECHANICAL SPECIFICATIONS TECHNICAL SPECIFICATIONS Insulated case and resin for Power Rating 250 W at 50 C continuous Mechanical Protection potting UL 94 V-0 Chassis Mounted 1000 W at 25 C for 10 s Resistive Element Cermet Temperature 250 ppm/C < 1 Substrate Alumina onto aluminum base Coefficient Standard 150 ppm/C > 1 End Connections Screws M4 (M5 on request) Dielectric Strength Tightening Torque L connections 7 kV 2 Nm RMS MIL STD 202 (301), Connections H connections 12 kV RMS min, 10 mA max. Weight 170 g 10 % 6 Insulation Resistance 10 M ENVIRONMENTAL SPECIFICATIONS Inductance 50 nH Thermal Resistance R 0.22 C/W th (j - c) Capacitance Resistor/ < 40 pF Temperature Range -55 C to 125 C Ground < 120 pF Climatic Category 55 / 125 / 56 Revision: 05-Jun-2019 Document Number: 50007 1 For technical questions, contact: sferfixedresistors vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc 91000 DD D 21 60 10.5 6 35.8 21 60 10.5 6 38.1 RPS 250 www.vishay.com Vishay Sfernice PERFORMANCE TESTS CONDITIONS REQUIREMENTS NF EN 140000 CEI 115 1 Momentary Overload < (0.25 % + 0.05 ) 4 Pr / 10 s / U = 5000 V L NF EN 140000 CEI 68214 Test Na Rapid Temperature Change 5 cycles < (0.25 % + 0.05 ) -55 C +125 C NF EN 140000 CEI 115 1 Load Life < (0.5 % + 0.05 ) 1000 h Pr at 70 C MIL STD 202 Method 103 B and D Humidity (Steady State) < (0.5 % + 0.05 ) 56 days RH 95 % RESISTANCE VALUE IN RELATION TO TOLERANCE AND TCR Ohmic Value < 1 > 1 Standard Tolerance 5 % 5 % Standard TCR (-55 C to +125 C) 250 ppm/C 150 ppm/C Tolerance on Request 1 %/ 2 %/ 10 % RECOMMENDATIONS FOR MOUNTING ONTO A HEATSINK Surfaces in contact must be carefully cleaned. The heatsink must have an acceptable flatness: From 0.05 mm to 0.1 mm / 100 mm. Roughness of the heatsink must be around 6.3 m. In order to improve thermal conductivity, surfaces in contact (alumina, heatsink) should be coated with a silicone grease (type SI 340 from Rhne-Poulenc or Dow 340 from Dow Corning). The fastening of the resistor to the heatsink is under pressure control of four screws (not supplied). RPS 250 Tightening Torque on Heatsink 3 Nm In order to improve the dissipation, either forced-air cooling or liquid cooling may be used. Do not forget to respect an insulation value between two resistors (dielectric strength in dry air 1 kV/mm). In any case the hot spot temperature, measured locally on the case must not exceed 125 C. Test should be performed by the user. CHOICE OF THE HEATSINK The user must choose the heatsink according to the working conditions of the component (power, room temperature). Maximum working temperature must not exceed 125 C. The dissipated power is simply calculated by the following ratio: T P = ----------------------------------------------------------------------------------------------------- R ++R R th (j - c) th (c - h) th (h - a) P: Expressed in W T: Difference between maximum working temperature and room temperature R : Thermal resistance value measured between resistive layer and outer side of the resistor. It is the thermal th (j - c) resistance of the component: (see Environmental Specifications). R : Thermal resistance value measured between outer side of the resistor and upper side of the heatsink. This is the th (c - h) thermal resistance of the interface (grease, thermal pad), and the quality of the fastening device. R : Thermal resistance of the heatsink. th (h - a) Example: R : for RPS 250 power dissipation 180 W at +50 C room temperature. th (c - a) T 125 C - 50 C 75 C T 75 R + R + R = ------- = -------- = 0.42 C/W th (j - c) th (c - h) th (h - a) P 180 R = 0.22 C/W th (j - c) R + R 0.42 C/W - 0.22 C/W 0.20 C/W th (c - h) th (h - a) Revision: 05-Jun-2019 Document Number: 50007 2 For technical questions, contact: sferfixedresistors vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc 91000