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 con tact
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Online database at https://assist.daps.dla.mil/.
AMSC N/A FSC 5905
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, WIREW OUND (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/, RW 37, RW38, RW39 1/, and R W47, 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.
MIL-PRF-26/3E
w/ Amendment 2
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 tem perat ur e
1/
Minimum insulation
resistance at end
of moisture resistance
Resistance temperature
characteristic (ppm/OC)
V 2/
N 3/ 350OC 100 Megohms
0 ±260 > 20 ohms
0 ±400 > 10 ohms to <20 ohms
0 +400, -200 > 1 ohm to <10 ohms
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 section s 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 docum ent s.
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 prece den ce. 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.
MIL-PRF-26/3E
w/ Amendment 2
3
3.2 Interfa ce and phy si cal dim ensi on. The resistor shall meet the interface and physical dimensions specified on
figure 1 and as specified herein.
Style A
±
0.062
B
(Max) C D
±
0.125
RW29
1.750
.172 (Min)
.625
RW30 1/ 1.000
.594
.187 (Min)
RW31
1.500
.312 +.016, -.125
RW32 1/
2.000
RW33
3.000
.187 (Min)
RW34 1/
3.000
.906
.516 +.046, -.047
.812
RW35
4.000
.500 +.062, -.031
RW36 1/
4.000
1.312
.750 +.156, -.047
1.219
RW37 6.000 .703 (Min)
RW38
8.000
.750 +.156, -.047
RW39 1/
12.000
RW47 10.500 .703 (Min)
1/ Not to be used for new design. For replacement purposes only.
NOTES:
1. Dimensions are in inches.
2. Metric equivalents are given for general inf or mat ion 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.
Inch
mm
Inch
mm
Inch
mm
Inch
mm
Inch
mm
Inch
mm
.016
.41
.125
3.18
.500
12.70
.812
20.62
1.750
44.45
10.500
266.70
.031
.79
.156
3.96
.516
13.11
.906
23.01
2.000
50.80
12.000
304.80
.046
1.17
.172
4.37
.594
15.09
1.000
25.40
3.000
76.20
.047 1.19 .187 4.75 .625 15.88 1.219 30.96 4.000 101.60
.062
1.57
.312
7.92
.703
17.86
1.312
33.32
6.000
152.40
.085
2.16
.328
8.33
.750
19.05
1.500
38.10
8.000
203.20
MIL-PRF-26/3E
w/ Amendment 2
4
3.3 Power rating. The power rating shall be as specified in table II, based on full load operation at an ambient
temperatur e of 25OC.
TABLE II. Power rating.
Resistor
style
Power rating
in watts Resistor
style
Power rating
in watts
Characteristic Characteristic
N
V
N
V
RW29 11 11 RW35 1/ 55 55
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
1/ 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 no mina l resi stan ce val ue s.
Resistor
style
Resistance
value (ohms)
Minimum
Resistance value (kohms)
Maximum
Characteristic
V
Characteristic
N
RW29
0.10
5.6
2.7
RW30 1/
2.7
---
RW31
6.8
3.3
RW32 1/
10
---
RW33
18
8.1
RW34 1/
30
---
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.
3.4.1 Standard resistance values. For standard resist anc e v alues 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 resi stan ce 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 nomi nal
resistance value. If center-tapped, the resistance tolerance between tap and terminal shall be ±10 percent.
MIL-PRF-26/3E
w/ Amendment 2
5
3.6 Therm al sho ck. The resistors shall not change in resistance in excess of ±(2 percent +0.05 ohm).
3.7 Short-time ov erloa d. The resistors shall not change in resistance in excess of ±(2 per c ent +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 per c ent +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 perc ent +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 per cent +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 an d inspection. Sampling and inspection shall be in accordance with MIL-PRF-26.
4.2 Short-time ov erloa d. The maximum voltages shall be in accordance with table IV.
TABLE IV. Maximum voltages for short-time overload.
Resistor
style Voltage
(Max) Resistor
style Voltage
(Max)
RW29 1200 RW35 3000
RW30 450 RW36 3000
RW31 1000 RW37 5000
RW32 1400 RW38 7000
RW33 2400 RW39 12000
RW34 2400 RW47 10000
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 Termi nal stre ngth. The applied force shall be 10 pounds.
MIL-PRF-26/3E
w/ Amendment 2
6
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 m ateriel 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 servic es system commands. Packaging data retrieval is available from the managing Mil itary
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 Acqui sit ion requ irements. 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 solici tat i on.
c. Packaging instructions (see 5.1).
d. Whether bracket as sem bly is required (see 6.4.1).
6.3 Supplementary insulation. Where potenti al to ground is ov er 500 volts, sup ple men tar y insu lat ion sho uld be
provided.
6.4 Mounting. These resistors should not be mounted by their terminals.
6.4.1 Brac ket as sem bli es. 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 acc ordance with figure 2.
FIGURE 2. Derating curve for high ambient temperatures.
Percent of rated power
100
80
60
40
20
0
25 50 100 150 200 250 300 350
Ambient Temperature (
O
C)
MIL-PRF-26/3E
w/ Amendment 2
7
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 typi cal oper at ing con dit ion s, on products that use such mater ia ls. Confor mal coating s appl ied
over top of a whisker-prone s urface will not prevent the formation of ti n 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 specifi c ation are marked with vertical lines to indicate modification
generated by this amendment. This was done as a convenience only and the Government as sumes no liability
whatsoever for any i naccuracies 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: Preparing activity:
Army - CR DLA - CC
Navy - EC
Air Force - 85 (Project 5905-2011-003)
DLA - CC
Review activities:
Army - MI
Navy - AS
Air Force - 19
NOTE: The activities listed above were interested in this document as of the date of thi s document. Since
organizations and responsibilities can change, you should verify the currency of the information above using the
ASSIST Online databa se at https://assist.daps.dla.mil.