rps 250 vishay sfernice document number: 50007 for technica l questions, contact: sfer@vishay.com www.vishay.com revision: 08-jun-06 31 power resistor for mounting onto a heatsink thick film technology features ? 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 developed for specific applications such as railroad electrical traction, this series can bear short overloads as high as fifte en times the nominal power. designed to be mounted onto a heatsink, these power resistors exhibit remarkable characteristics. dimensions in millimeters mechanical specifications mechanical protection insulated case substrate alumina onto aluminum base resistive element cermet end connections screws m4, (m5 on request) tightening torque on connections 2 nm weight 170 g 10 % environmental specifications thermal resistance r th (j-c) 0.22 c/w temperature range - 55 c + 125 c climatic category 55/125/56 rohs compliant ? tolerance unless stated: 0.2 mm 73 56 7 . 5 57 34 ? 7.2 ? 4.2 8 . 5 3 2 m4 useful depth: 8 rps 250d 5 . 0 1 0 6 1 2 ? 26 1 16.5 electrical specifications resistance range 0.24 to 1m e24 series tolerances 1 % to 10 % power rating chassis mounted 250 w 1000 w at 50 c continuous at 25 c for 10 seconds temperature coefficient standard 250 ppm/c < 1 150 ppm/c > 1 limiting element voltage 5 kvrms dielectric strength mil std 202 (301), 1 minute, 10 ma max l connections 7 kvrms h connections 12 kvrms insulation resistance > 10 6 m inductance < 50 nh capacitance resistor/ ground < 40 pf < 120 pf
www.vishay.com for technical ques tions, contact: sf er@vishay.com document number: 50007 32 revision: 08-jun-06 rps 250 vishay sfernice power resistors for m ounting onto a heatsink thick film technology 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 dissipat ed power is simply calculated by the following ratio: p: expressed in w t: difference between maximum working te mperature and room temperature. r th : (j-c): thermal resistance value measur ed between resistive layer and outer side of the resistor. it is the thermal resistance of the component: (see sp ecifications environmental paragraph). r th : (c-a): thermal resistance value measured between ou ter side of the resistor and room temperature. it is the thermal resistance of the heatsink itself (t ype, shape) and the quality of the fastening device. example: r th : (c-a) for rps 250 power dissipation 180 w at + 50 c room temperature. t 125 c - 50 c 75 c r th (j-c) + r th (c-a) = = = 0.42 c/w r th (j-c) = 0.22 c/w r th (c-a) 0.42 c/w - 0.22 c/w 0.20 c/w recommendations for mounting onto a heatsink surfaces in contact must be carefully cleaned. the heatsink mu st 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 impr ove thermal conductivity, surfaces in contact should be coated with a silicone grease (type si 340 from rh?ne-poulenc or dow 340 from dow corning). the fastening of the resistor to the heatsink is under pressure control of two screws (tightening torque 3 nm). in order to improve the dissipation, either fo rced-air cooling or liquid cooling may be used. do not forget to respect an insulation value between two resistors (dielectric st rength in dr y air 1 kv/mm). in any case the hot spot temperature, measur ed locally on the case must not exceed 125 c. test should be performed by the user. performance tests conditions typical drifts momentary overload nf en 140 000 cei 115_1 4 pr/10 s < (0.25 % + 0.05 ) rapid temperature change nf en 140 000 cei 68214 test na 5 cycles - 55 c + 125 c < (0.25 % + 0.05 ) load life nf en 140 000 cei 115_1 1000 h pr at 70 c < (0.5 % + 0.05 ) humidity (steady state) mil std 202 method 103 b and d 56 days r.h. 95 % < (0.5 % + 0.05 ) resistance value in relati on to tolerance and tcr ohmic value < 1 > 1 standard tolerance 5 % 5 % standard tcr 250 ppm/c 150 ppm/c tolerance on request 1 % - 2 % - 10 % p t r th jc ? () r th ca ? () + [] -------------------------------------------------------------------- - 1 () = t p ------- 75 180 --------- -
rps 250 power resistor for mount ing onto a heatsink thick film technology vishay sfernice document number: 50007 for technica l questions, contact: sfer@vishay.com www.vishay.com revision: 08-jun-06 33 overloads in any case the applied voltage must be lower than 2.5 un. u maxi < 2.5 un < 12 500 v. short time overload: 4 pn/10 seconds accidental overload: the values indicated on the graph below are applic able to resistors in air or mounted onto a heatsink. energy curve power rating chart the temperature of the heat sink should be maintained in the limit specified. to improve the thermal conductivity, surfaces in contact should be coated with a silicone grease. marking series, style, ohmic value (in ), tolerance in %, manufactu ring date, vishay trademark ordering information rps 250 dl 250u 1 % za3 b015 e model style connections optional h: dielectric strength 12 kv l: dielectric strength 7 kv resistance value tolerance optional 1 % 2 % 5 % 10 % custom design options on request special tcr, shape, etc. packaging lead (pb)-free sap part numbering guidelines rps 0250 dl 2500 f b za3 model style connections ohmic value tolerance packaging design energy in joules overload duration in seconds 1 s 0.13 1 10 100 1000 10 000 10 s 100 s 1 ms 1 s 10 ms 100 ms % rated power 0 20 40 60 80 100 120 140 heatsink temperature in degrees celsius 0 20 40 60 80 100 packaging box of 15 u nits
document number: 91000 www.vishay.com revision: 18-jul-08 1 disclaimer legal disclaimer notice vishay all product specifications and data are subject to change without notice. vishay intertechnology, inc., its affiliates, agents, and employees, and all persons acting on its or their behalf (collectively, ?vishay?), disclaim any and all liability fo r any errors, inaccuracies or incompleteness contained herein or in any other disclosure relating to any product. vishay disclaims any and all li ability arising out of the use or application of any product describ ed herein or of any information provided herein to the maximum extent permit ted by law. the product specifications do not expand or otherwise modify vishay?s terms and conditions of purcha se, including but not limited to the warranty expressed therein, which apply to these products. no license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted by this document or by any conduct of vishay. the products shown herein are not designed for use in medi cal, life-saving, or life-sustaining applications unless otherwise expressly indicated. customers using or selling vishay products not expressly indicated for use in such applications do so entirely at their own risk and agree to fully indemnify vishay for any damages arising or resulting from such use or sale. please contact authorized vishay personnel to obtain written terms and conditions regarding products designed for such applications. product names and markings noted herein may be trademarks of their respective owners.
|
