INCH-POUND MIL-PRF-26/3E w/ Amendment 2 18 November 2010 SUPERSEDING MIL-PRF-26/3E w/ Amendment 1 13 August 2007 PERFORMANCE SPECIFICATION SHEET RESISTOR, FIXED, WIREWOUND (POWER TYPE), STYLES RW29, RW30 1/, RW31, RW32 1/, RW33, RW34 1/, RW35, RW36 1/, RW37, RW38, RW39 1/, and RW47 This specification is approved for use by all Departments and Agencies of the Department of Defense. The requirements for acquiring the product described herein shall consist of this specification sheet and MIL-PRF-26. 1. SCOPE 1.1 Scope. This specification covers the associated requirements for styles RW29, RW30 1/, RW31, RW32 1/, RW33, RW34 1/, RW35, RW36 1/, RW37, RW38, RW39 1/, and RW47, wirewound inductive (V) and noninductive (N) resistors. 1.2 Part or Identifying Number (PIN). Resistors covered by this specification are identified by a PIN which consists of the style designation, characteristic, and coded resistive value. The PIN is derived in accordance with MIL-PRF-26 and is in the following form: RW29 | V | 100 | Style (1.2.1) Characteristic (1.2.2) Resistance (1.2.3) 1.2.1 Style. The style is identified by the two-letter symbol "RW" followed by a two-digit number. 1.2.2 Characteristic. The characteristic is identified by a single letter that identifies the maximum continuous operating temperature (surface hot spot), the minimum insulation resistance value at the end of the moisture resistance test, and the resistance temperature characteristic in accordance with table I. 1.2.3 Resistance. The nominal resistance expressed in ohms is identified by a three-digit number; the first two digits represent significant figures and the last digit specifies the number of zeroes to follow. When resistance values less than 10 ohms are required, the letter "R" is substituted for one of the significant digits to represent the decimal point. When the letter "R" is used, succeeding digits of the group represent significant figures as shown in the following example. R10 = 0.1 ohm 1R0 = 1.0 ohm 1/ Not to be used for new design. For replacement purposes only. Comments, suggestions, or questions on this document should be addressed to: DLA Land and Maritime, ATTN: VAT, Post Office Box 3990, Columbus, Ohio 43218-3990 or by email Resistor@dla.mil. Since contact information can change, you may want to verify the currency of this address information using the ASSIST Online database at https://assist.daps.dla.mil/. AMSC N/A FSC 5905 MIL-PRF-26/3E w/ Amendment 2 Minimum and maximum resistance values are as specified herein. The standard values for every decade should follow the sequence demonstrated for the "10 to 100" decade in accordance with MIL-PRF-26. TABLE I. Characteristic. Symbol Maximum continuous operation temperature 1/ Minimum insulation resistance at end of moisture resistance Resistance temperature O characteristic (ppm/ C) 0 260 > 20 ohms 0 400 > 10 ohms to <20 ohms V 2/ O 350 C 100 Megohms 0 +400, -200 > 1 ohm to <10 ohms N 3/ 0 +500, -100 > 0.499 ohm to <1 ohm 0 +650, -100 > 0.1 ohm to < 0.499 ohm 1/ This temperature is also the maximum permissible hot-spot surface temperature. 2/ Inductive wirewound. 3/ Noninductive wirewound. 2. APPLICABLE DOCUMENTS 2.1 General. The documents listed in this section are specified in sections 3 and 4 of this specification. This section does not include documents cited in other sections of this specification or recommended for additional information or as examples. While every effort has been made to ensure the completeness of this list, document users are cautioned that they must meet all specified requirements documents cited in sections 3 and 4 of this specification, whether or not they are listed. 2.2 Government documents. 2.2.1 Specifications, standards, and handbooks. The following specifications, standards, and handbooks form a part of this document to the extent specified herein. Unless otherwise specified, the issues of these documents are those cited in the solicitation or contract (see 6.2). DEPARTMENT OF DEFENSE SPECIFICATION MIL-PRF-26 - Resistors, Fixed, Wire Wound (Power Type), General Specification for. (Copies of these documents are available online at https://assist.daps.dla.mil/quicksearch/ or from the Standardization Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094). 2.3 Order of precedence. Unless otherwise noted herein or in the contract, in the event of a conflict between the text of this document and the references cited herein (except for related specification sheets), the text of this document takes precedence unless otherwise noted. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 3. REQUIREMENTS 3.1 General. The requirements for acquiring the product described herein shall consist of this document and MIL-PRF-26. 2 MIL-PRF-26/3E w/ Amendment 2 3.2 Interface and physical dimension. The resistor shall meet the interface and physical dimensions specified on figure 1 and as specified herein. A 0.062 Style RW29 RW30 1/ RW31 RW32 1/ RW33 RW34 1/ RW35 RW36 1/ RW37 RW38 RW39 1/ RW47 1.750 1.000 1.500 2.000 3.000 3.000 4.000 4.000 6.000 8.000 12.000 10.500 B (Max) D 0.125 C .500 .172 (Min) .187 (Min) .594 .312 +.016, -.125 .625 .187 (Min) .516 +.046, -.047 .500 +.062, -.031 .750 +.156, -.047 .703 (Min) .906 1.312 .812 1.219 .750 +.156, -.047 .703 (Min) 1/ Not to be used for new design. For replacement purposes only. Inch .016 .031 .046 .047 .062 .085 mm .41 .79 1.17 1.19 1.57 2.16 Inch .125 .156 .172 .187 .312 .328 mm 3.18 3.96 4.37 4.75 7.92 8.33 Inch .500 .516 .594 .625 .703 .750 mm 12.70 13.11 15.09 15.88 17.86 19.05 Inch .812 .906 1.000 1.219 1.312 1.500 mm 20.62 23.01 25.40 30.96 33.32 38.10 Inch 1.750 2.000 3.000 4.000 6.000 8.000 mm 44.45 50.80 76.20 101.60 152.40 203.20 NOTES: 1. Dimensions are in inches. 2. Metric equivalents are given for general information only. 3. Unless otherwise specified, tolerance is 0.010 (0.25 mm). FIGURE 1. Styles RW29, RW30, RW31, RW32, RW33, RW34, RW35, RW36, RW37, RW38, RW39, and RW47. 3 Inch 10.500 12.000 mm 266.70 304.80 MIL-PRF-26/3E w/ Amendment 2 3.3 Power rating. The power rating shall be as specified in table II, based on full load operation at an ambient O temperature of 25 C. TABLE II. Power rating. Power rating in watts Resistor style N 1/ Resistor style Characteristic V Power rating in watts Characteristic N 55 V 55 RW29 11 11 RW35 1/ RW30 --- 11 RW36 1/ --- 78 RW31 14 14 RW37 1/ 113 113 RW32 --- 17 RW38 1/ 159 159 RW33 1/ 26 26 RW39 1/ --- 240 RW34 1/ --- 43 RW47 1/ 210 210 The power rating of center-tapped resistors shall be 90 percent of those shown. 3.4 Resistance. The minimum and maximum nominal resistance values shall be as specified in table III. TABLE III. Minimum and maximum nominal resistance values. Resistance value (kohms) Maximum Characteristic Characteristic V N RW29 5.6 2.7 RW30 1/ 2.7 --RW31 6.8 3.3 RW32 1/ 10 --RW33 18 8.1 RW34 1/ 30 --0.10 RW35 43 20 RW36 1/ 56 --RW37 91 43 RW38 150 75 RW39 1/ 200 --RW47 180 81 1/ Not to be used for new design. For replacement purposes only. Resistor style Resistance value (ohms) Minimum 3.4.1 Standard resistance values. For standard resistance values see MIL-PRF-26. 3.5 Resistance tolerance. These resistors have a resistance range of 0.10 ohms to 200 kohms with the following resistance tolerances: a. Resistors of less than 1 ohm in resistance value shall have a tolerance of 10 percent of the nominal resistance value. If center-tapped, the resistance tolerance between tap and terminal shall be 10 percent. b. Resistors of 1 ohm and over in resistance value shall have a tolerance of 5 percent of the nominal resistance value. If center-tapped, the resistance tolerance between tap and terminal shall be 10 percent. 4 MIL-PRF-26/3E w/ Amendment 2 3.6 Thermal shock. The resistors shall not change in resistance in excess of (2 percent +0.05 ohm). 3.7 Short-time overload. The resistors shall not change in resistance in excess of (2 percent +0.05 ohm). 3.8 High-temperature exposure. The resistors shall not change in resistance in excess of (2 percent +0.05 ohm). 3.9 Moisture resistance. The resistors shall not change in resistance in excess of (2 percent +0.05 ohm). 3.10 Low-temperature storage. The resistors shall not change in resistance in excess of (2 percent +0.05 ohm). 3.11 Life. The resistors shall not change in resistance in excess of (3 percent +0.05 ohm). 3.12 Solderability. Solderability is applicable to this specification 3.13 Terminal strength. The resistors shall not change in excess of (1 percent +.05 ohm). 3.14 Dielectric withstanding voltage (barometric pressure, reduced, not applicable). The resistors shall not change in resistance in excess of (.1 percent +0.05 ohm). 3.15 Pure tin. The use of pure tin, as an underplate or final finish is prohibited both internally and externally. Tin content of resistor components and solder shall not exceed 97 percent, by mass. Tin shall be alloyed with a minimum of 3 percent lead, by mass (see 6.6). 4. VERIFICATION 4.1 Sampling and inspection. Sampling and inspection shall be in accordance with MIL-PRF-26. 4.2 Short-time overload. The maximum voltages shall be in accordance with table IV. TABLE IV. Maximum voltages for short-time overload. Resistor style Voltage (Max) Resistor style RW29 1200 RW35 3000 RW30 450 RW36 3000 RW31 1000 RW37 5000 RW32 1400 RW38 7000 RW33 2400 RW39 12000 RW34 2400 RW47 10000 Voltage (Max) 4.3 Dielectric withstanding voltage. 4.3.1 Atmospheric pressure. The magnitude of test voltage shall be 1,000 volts rms. 4.3.2 Barometric pressure (reduced). The test voltage shall be 200 volts rms. 4.4 Terminal strength. The applied force shall be 10 pounds. 5 MIL-PRF-26/3E w/ Amendment 2 5. PACKAGING. 5.1 Packaging. For acquisition purposes, the packaging requirements shall be as specified in the contract or order (see 6.2). When packaging of materiel is to be performed by DoD or in-house contractor personnel, these personnel need to contact the responsible packaging activity to ascertain packaging requirements. Packaging requirements are maintained by the Inventory Control Point's packaging activity within the Military Service or Defense Agency, or within the military services system commands. Packaging data retrieval is available from the managing Military Department's or Defense Agency's automated packaging files, CD-ROM products, or by contacting the responsible packaging activity. 6. NOTES (This section contains information of a general or explanatory nature that may be helpful, but is not mandatory.) 6.1 Notes. In addition to the notes specified herein, the notes specified in MIL-PRF-26 are applicable to this specification. 6.2 Acquisition requirements. Acquisition requirements are as specified in MIL-PRF-26. a. Title, number, and date of this specification, and the complete PIN (see 1.2). b. Unless otherwise specified (see 2.1), the versions of the individual documents referenced will be those in effect on the date of release of the solicitation. c. Packaging instructions (see 5.1). d. Whether bracket assembly is required (see 6.4.1). 6.3 Supplementary insulation. Where potential to ground is over 500 volts, supplementary insulation should be provided. 6.4 Mounting. These resistors should not be mounted by their terminals. 6.4.1 Bracket assemblies. When required, bracket assemblies (mounting hardware) are available for these resistors under MS75009, Bracket Assembly, Resistor (Power type). 6.5 Derating. Resistors shall be derated, when necessary, in accordance with figure 2. Percent of rated power 100 80 60 40 20 0 25 50 100 150 200 250 300 350 O Ambient Temperature ( C) FIGURE 2. Derating curve for high ambient temperatures. 6 MIL-PRF-26/3E w/ Amendment 2 6.6 Tin whisker growth. The use of alloys with tin content greater than 97 percent, by mass, may exhibit tin whisker growth problems after manufacture. Tin whiskers may occur anytime from a day to years after manufacture and can develop under typical operating conditions, on products that use such materials. Conformal coatings applied over top of a whisker-prone surface will not prevent the formation of tin whiskers. Alloys of 3 percent lead, by mass, have shown to inhibit the growth of tin whiskers. For additional information on this matter, refer to ASTM-B545 (Standard Specification for Electrodeposited Coatings of Tin). 6.7 Amendment notations. The margins of this specification are marked with vertical lines to indicate modification generated by this amendment. This was done as a convenience only and the Government assumes no liability whatsoever for any inaccuracies in these notations. Bidders and contractors are cautioned to evaluate the requirements of this document based on the entire content irrespective of the marginal notations and relationship. Custodians: Army - CR Navy - EC Air Force - 85 DLA - CC Preparing activity: DLA - CC (Project 5905-2011-003) Review activities: Army - MI Navy - AS Air Force - 19 NOTE: The activities listed above were interested in this document as of the date of this document. Since organizations and responsibilities can change, you should verify the currency of the information above using the ASSIST Online database at https://assist.daps.dla.mil. 7