High Voltage
Thick Film Resistors
F Series
Construction
The Cermetox
®
thick film is fired on to the surface of a high
quality ceramic former. Turned brass end caps are fitted. A
helical cut is made into the film to adjust its ohmic value and
finally a sleeve is fitted to provide mechanical protection and
electrical insulation. Resistors for use in oil SF6 can be
supplied with a lacquer protection instead of the sleeve.
Welwyn Components
Screw Terminations:
Styles TU and KU
Material:
Screw Thread:
Turned brass
All caps are tapped UNF - 10 x 4.2
deep. UNF - 10 is 32 TPI, 60° thread
angle 4.72 ±0.07 mm outside diameter,
3.83 mm core diameter.
All KU & TU resistors are supplied with
8 mm long screwed brass studs.
Coupling Stud:
Terminations
Three styles of termination are available to permit resistors to
be screwed together in a series chain, with the end members
having axial wires for soldering.
Wire Terminations:
Styles D and KU
Non standard wire terminations
available upon request.
Material:
Strength:
Solderability:
Solder coated copper wire
The terminations meet the requirements
of IEC 68.2.21.
The terminations meet the requirements
of IEC 115-1, Clause 4.17.3.2.
Marking
Type reference, resistance value, tolerance and date code are
legend marked. The resistance values conform to IEC 62.
Solvent Resistance
The lacquer and protective sleeve provide excellent resistance
to all normal industrial cleaning solvents suitable for printed
circuits.
Performance Data
Maximum
Load at rated power: 1000 hours at 20°C
Shelf life: 12 months at room temperature
Derating from rated power at 20°C
Noise (µV/V in a decade of frequency)
Voltage coefficient of resistance
ppm/V
∆R%
∆R%
Zero at 100°C
<2.5
<25
5
Typical
1
0.5
Application Notes
Mounting
Due to the high voltage which can appear between the end
cap and any adjacent metal part, resistors should be mounted
at an adequate distance from other conductors.
Resistors may be screwed together to provide an assembly
which will be capable of withstanding any desired voltage,
providing no individual resistor is subjected to a greater stress
or power dissipation than is recommended in this data sheet.
For some high voltage applications it is required to immerse
the components in oil or gas to reduce the effects of corona
and surface tracking. A special lacquer is available, suitable
for immersion in transformer oil of SF6.
When resistors are required to be potted, the preferred
encapsulant is a silicone compound.
For voltage dividers with a low resistance section below the
minimum available value of an F43 resistors, it is entirely
suitable to use an RC Series resistor, available down to 1 ohm.
© 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
202
Matched Sets
Matched sets can be supplied for use as voltage dividers.
These may be screwed together to form sticks and, by
selecting the KU type of termination, a wire connection can
be provided at each end of the stick.
Enquiries are welcomed for special resistors and sets when
resistor length, operating voltage or resistance vale is outside
the catalogued range.
Packaging
All components are supplied in boxes.
Standard Quantities Per Box
All Types
10 or 20 per box
Issue B · 03.02
WELWYN [ WELWYN COMPONENTS LIMITED ]
