Chassis Mounting
Wirewould Resistors
WH SERIES
●High quality ceramic substrate
●All welded construction
●Anodised extruded aluminium case
●High power dissipation for size
●Suitable for severe environments
●Designed for excellent thermal conductivity
to heatsink
Electrical Data
WH5 EH10 WH25 WH50 NOTES
Power rating at 25°C watts 10 15 25 50* Mounted on
standard heatsink
Resistance range ohms 0.01 to 10k 0.01 to 20k 0.01 to 44k
0.015 to 120k
TCR (-55° to 200°C) ppm/°C <10Ω: ±75 ≥to <100 : ±50 ≥100Ω: ±25
Resistance tolerance % 1, 2, 5, 10
Low value limits ohms 1 at 1% 0.5 at 2% 0.05 at 5% 0.01 at 10% WH50 0.015 at 10%
APPROVED CECC 40203 - 006 AA BA CA DA
Power rating at 25°C watts 10 15 25 40 Mounted on
standard heatsink
Resistance range ohms 0.05 to 3.4k 0.05 to 15k 0.05 to 33k
0.05 to 82k
TCR (-55° to 200°C) ppm/°C ≥5Ω≤10Ω± 100 >10Ω±50
Resistance tolerance % 1, 2, 5
Low value limits ohms 1 at 1% 0.5 at 2% 0.05 at 5%
Limiting element voltage volts 150 250 500 1250
Standard values E24 preferred range Other values
to special order
Thermal impedance °C/watt 16.0 10.0 6.0 3.5 Mounted on
standard heatsink
Operating temperature range °C -55 to 200
*For load at maximum rating mount on heatsink 30.5 cm x 30.5 cm x 1.5 mm
© Welwyn Components Limited
Bedlington, Northumberland NE22 7AA, England Tel: 01670 822181 Fax: 01670 829465 Web: http://www.Welwyn-TT.co.uk Issue A 07/99
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.
CONSTRUCTION
Cap and lead assemblies are fitted to a high purity ceramic
substrate. The resistive element is wound onto the
substrate and welded to the caps. The wound rod is then
moulded and fitted into an aluminium housing to give
optimum stability and reliability.
TERMINATIONS
Material Solder dipped, copper clad steel wire.
Strength The terminations meet the requirements of
IEC 68.2.21
Solderability The terminations meet the requirements of
IEC 115-1, Clause 4.17.3.2
MARKING
The resistors are legend marked with type reference,
resistance value and tolerance. Values are marked in
accordance with IEC 62.
SOLVENT RESISTANCE
Resistor and marking withstand all accepted industrial
cleaning fluids.
Physical Data
DIMENSIONS (MM)
Type A B C E F
Max ±0.3 ±0.3 Min Max
WH5 30.0 12.4 11.3 1.9 17
WH10 36.5 15.9 14.3 1.9 21
WH25 51.0 19.8 18.3 2.8 28
WH50 72.5 21.4 39.7 2.8 30
TypeGHLMN
Max Dia ±0.2 Max ±0.5 Max
WH5 9 2.4 17.0 4.3 1.8
WH10 11 2.4 21.0 5.2 2.2
WH25 15 3.3 29.0 7.2 2.6
WH50 16 3.3 51.0 7.9 2.6
Performance Data
CECC ACTUAL NOTES
40203-006 MAXIMUM TYPICAL
Load at commercial rating: 1000 hrs at 25°C ∆R % 1.0 1.0 0.4
Load at CECC rating: 1000 hours at 25°C ∆R % 1.0 1.0 0.4
Dry heat: 100 hours at 200°C ∆R % 1.0 1.0 0.4
Derating from 25°C
Zero at 200°C
Short term overload ∆R % 1.0 1.0 0.2
Climatic sequence ∆R % 1.0 1.0 0.4
Climatic category 55/200/56
Long term damp heat ∆R % 1.0 0.5 0.2
Temperature rapid change ∆R % 0.25 0.25 0.1
Resistance to solder heat ∆R % 0.25 0.25 0.05
Vibration and bump ∆R % 0.25 0.25 0-.025
Noise (in decade of frequency) µV/V
Not specified
zero zero
Insulation resistance. ohms >1Gohm >20Tohm >100Gohm
Isolation voltage : WH5 and 10 volts AC peak 1000 min 1500 min See application
: WH25 and 50 volts AC peak 2000 min 3000 min notes
Chassis Mounting
Wirewound Resistors
WH SERIES
© Welwyn Components Limited
Bedlington, Northumberland NE22 7AA, England Tel: 01670 822181 Fax: 01670 829465 Web: http://www.Welwyn-TT.co.uk Issue A 07/99
Chassis Mounting
Wirewound Resistors
WH SERIES
510
10
20
30
40
50
50 100 500 1000
HEATSINK SURFACE AREA (cm2)
MAXIMUM DISSIPATION (WATTS)
CA
CA
BA
AA
544cm2
410cm2
RATED DISSIPATION AT 25°C
RATED DISSIPATION AT 70°C
25°C
25°C
25°C
70°C
70°C
70°C
CECC 40 STYLE
APPLICATION NOTES
Reference aluminium heatsink dimension
CECC 40203-006 L W H REFERENCE
CM CM CM
AREA SQ. CM
AA, BA 15.5 10 5 410
CA, DA 18 13 5 544
Aluminium thickness 1mm
Reference chassis
LW
H
Derating must be applied when resistors are
mounted on a heat sink of smaller dimensions than
defined in the table for reference heatsink.
It is recommended that the resistor base should be
coated with silicone grease before mounting to
obtain the stated operating characteristics.
The grease increases thermal conductivity to the
heatsink.
After soldering care should be taken to ensure that
there are no flux residues on the moulding
compound, otherwise insulation resistance will be
reduced.
PACKAGING
Resistors are packed in plastic bags and boxed for
maximum protection.
WH50 ONLY
To load at maximum commercial rating (50W) mount
on heatsink 30.5cm x 30.5cm x 1.5mm.
© Welwyn Components Limited
Bedlington, Northumberland NE22 7AA, England Tel: 01670 822181 Fax: 01670 829465 Web: http://www.Welwyn-TT.co.uk Issue A 07/99
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.
