General-Purpose Failsafe
Moulded Wirewound Resistors
SP20/SP20F Series
Welwyn Components
•
Drop-in replacement for BW20/BW20F
•
Predictable fusing characteristics
•
1 watt rated with 1/2 watt dimensions
•
0.1 ohm to 1200 ohms
•
Weldable and solderable magnetic leads
Electrical Data
Type
EIA RS-344 Style
MIL-R-11 Style
Resistance Range
Tolerance
Power rating
ohms
%
watts
1 at 50°C
0.75 at 70°C
0.5 at 100°C
Derating to 0 at 160°C
Maximum continuous working voltage
Minimum insulation resistance
Minimum dielectric withstanding volts
Reduced pressure
Hotspot temperature rise
Current noise
dry
wet
ATM
RMS
√PR
10,000 Meg
100 Meg
700V
450V
120°C at 1 watt
Negligible
0R1 to 1k2
±5, ±10
1 at 50°C
0.75 at 70°C
-
Derating to 0 at 160°C
SP20
CRU 1
RC20/RC32
0R1 to 1k
SP20F
Physical Data
Dimensions (mm)
Type
SP20
SP20F
L
9.91±0.25
9.91±0.25
D
3.56±0.20
3.56±0.20
d
0.813±0.05
0.813±0.05
f
38.1±3.2
38.1±3.2
d
D
L
f
Resistive Element
All resistor types have resistance alloy winding on a braided
fibreglass substrate. Intermediate silicone coatings are used to
enhance processibility and to provide protection to the
resistive element.
Encapsulation
The SP20 and SP20F are encapsulated utilizing a compression
molded phenolic plastic material. The SP20F has a flame
resistance coating applied over the resistive element to
provide flammmability protection when destructive overloads
may occur.
Termination
The SP20 and SP20F resistors are terminated using an alloy
coated copper flashed steel lead welded to a cap of the same
material. This termination assembly is mechanically crimped,
utilizing an improved crimp design, to the resistive element.
Marking
All products are marked utilizing heat and solvent resistant
colour code bands consistent with EIA/MIL requirements. The
first band is double width to designate wirewound
construction. A fifth band, blue in colour, is used for
flameproof identification.
General Note
Welwyn Components reserves the right to make changes in product specification without notice or liability.
All information is subject to Welwyn’s own data and is considered accurate at time of going to print.
A subsidiary of
TT electronics plc
Issue B · 03.02
© Welwyn Components Limited
· Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
95
WELWYN [ WELWYN COMPONENTS LIMITED ]
