WFF Datasheet PDF - Welwyn Components Limited

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WFF
Welwyn Components Limited

Part Number WFF
Description Fast Fusible Metal Film Resistors
Page 3 Pages


WFF datasheet pdf
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Fast Fusible Metal
Film Resistors
WFF Series
Low power fusing
Predictable fusing characteristics
Flameproof protection
www.DataSheet4U.com
Welwyn Components
Electrical Data
Power rating at 70˚ C
Resistance range
Limiting element voltage
TCR
Resistance tolerance
Standard values
Thermal impedance
Ambient temperature range
watts
ohms
volts
ppm/˚ C
%
˚ C/watt
˚C
WFF1/4
0.25
0R1 - 10K
250
150
WFF1/2
0.5
0R10 - 27K
350
250
5
E24 preferred
120
-55 to 155
WFF1
1
0R2 - 1K5
350
100
Physical Data
Dimensions (mm) & Weight (g)
Type L D f
max max min
WFF1/4 6.2
2.53 21.0
WFF1/2 9.0
3.4 19.6
WFF1 12.5 4.2 17.8
d PCB Min.
nom mounting bend
centres radius
0.6 10.2 0.6
0.8 12.7 1.2
0.8 18.4 1.2
Wt.
nom
0.3
0.6
0.9
dD
L
f
Construction
The metal film is deposited on a high purity ceramic rod. End
caps are force fitted and termination wires welded to the
caps. The resistive film is adjusted to the required value by a
special helical cut. A fuse aid coating is then applied. Finally a
cement protection is applied to the resistor body prior to
marking with indelible ink.
Terminations
Material
Solder-coated copper wire.
Strength
The terminations meet the requirements of
IEC68.2.21.
Solderability The terminations meet the requirements of
IEC 115-1 Clause 4.17.3.2.
Marking
Resistors are colour coded with 5 bands. Four of the bands
are used to indicate values and tolerance, with IEC 62 colours
being used. A fifth yellow band denotes constant voltage
fusibility.
Solvent Resistance
The body protection and marking are resistant to all normal
industrial cleaning solvents suitable for printed circuits.
Flammability
The resistors will not burn or emit incandescent particles
under any condition of applied temperature or power
overload.
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.
© 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
A subsidiary of
TT electronics plc
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Fast Fusible Metal
Film Resistors
WFF Series
Welwyn Components
Performance Data
Load: 1000 hrs at 70˚ C
Shelf life: 12 months at room temperature
Derating from rated power at 70˚ C
Temperature rapid change
Resistance to solder heat
www.DataShePetu4lUs.ecoHmandling Graphs
Graph 1
10000
1.2/50μS Pulse Withstand
Maximum
R% 3
R% 2
zero at 155˚ C
R% 0.5
R% 0.5
Graph 2
10000
10/700μS Pulse Withstand
1000
1000
100
10
10
WFF 1/4
WFF 1/2
WFF 1
100
1000
10000
Value (OHMS)
100000
100
10
10
WFF 1/4
WFF 1/2
WFF 1
100
1000
10000
Value (OHMS)
Above tests carried out in accordance with IEC 115.1. Change of value after test ±1%
100000
Graph 3
10000
1000
Maximum peak pulse voltage
as a function of pulse duration (ti)
WFF 1/4
WFF 1/2
WFF 1
100
0.0001
0.0010
0.0100
ti (s)
0.1000 1.0000
Graph 4
100
Maximum peak pulse power
as a function of pulse duration (ti)
10
WFF 1/4
1 WFF 1/2
WFF 1
0
0.0001
0.0010
0.0100
ti (s)
0.1000
1.0000
Test Method (for graph 3 and 4)
The resistor is subject to 10,000 pulses as shown in figure
(1). Maximum resistance change due to test will not
exceed 1%. Maximum pulse voltages are detailed in graph
3 above.
For any combination of power and pulse length (ti). tp is
determined by the need to ensure that the average power
does not exceed the rated power.
tp = Applied Pulse Power
x ti
Rated Power
Figure 1
ti
tp
Time (secs)
© 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
162
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Fast Fusible Metal
Film Resistors
WFF Series
www.DataSheet4U.com
Welwyn Components
Packaging
All resistors are supplied tape packed ready for loading
onto automatic sequencing and insertion machines.
The standard taping method and critical dimensions are
shown in figure 2.
Lead Formed resistors can also be supplied. Standard
options of Lancet, Radial and Goalpost forming are shown
in Lead Form Information section.
Figure 2
52
Body Location f
1.4 m
Standard Quantities Per Package
Type
Large ammo pack
WFF1/4
5000
WFF1/2
2500
WFF1
1500
*Contact Welwyn for R10 - 1R0 fusing data
Fusing (Constant voltage)
After fusing the final resistance value will be 50 times the
initial value.
© 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
Issuee DE · 031.0067
163



WFF datasheet pdf
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