Fast Fusible Metal
Film Resistors
WFF Series
Welwyn Components
•
•
•
Low power fusing
Predictable fusing characteristics
Flameproof protection
Electrical Data
WFF
1
/
4
Power rating at 70˚ C
Resistance range
Limiting element voltage
TCR
Resistance tolerance
Standard values
Thermal impedance
Ambient temperature range
˚ C/watt
˚C
150
watts
ohms
volts
ppm/˚ C
%
0.25
0R1 - 10K
250
WFF
1
/
2
0.5
0R10 - 27K
350
250
5
E24 preferred
120
-55 to 155
100
WFF1
1
0R2 - 1K5
350
Physical Data
Dimensions (mm) & Weight (g)
Type
L
max
6.2
9.0
12.5
D
max
2.3
2.5
3.4
4.2
f
min
21.0
19.6
17.8
d
nom
0.6
0.8
0.8
PCB
mounting
centres
10.2
12.7
18.4
Min.
bend
radius
0.6
1.2
1.2
Wt.
nom
0.3
0.6
0.9
d
D
WFF
1
/
4
WFF
1
/
2
WFF1
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.
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.
Terminations
Material
Strength
Solder-coated copper wire.
The terminations meet the requirements of
IEC68.2.21.
Flammability
The resistors will not burn or emit incandescent particles
under any condition of applied temperature or power
overload.
Solderability
The terminations meet the requirements of
IEC 115-1 Clause 4.17.3.2.
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
E 01.07
Issue
D
·
03.06
© 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
161
WELWYN [ WELWYN COMPONENTS LIMITED ]
