Aluminium Housed
Wirewound Resistors
WH Series
•High power dissipation for size
•All welded construction
•Suitable for severe environments
•Designed for excellent thermal
conductivity to heatsink
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
107
WH5 WH10 WH25 WH50 Notes
Power rating at 25°C watts 10 15 25 50*
Mounted on standard heatsink
Resistance range ohms 0R01 to 10K 0R01 to 20K 0R01 to 44K 0R015 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% WH50 0.015 at 10%
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
Ambient 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
Electrical Data
Issue D · 03.06
A subsidiary of
TT electronics plc
Welwyn Components
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 which will withstand all
accepted industrial cleaning fluids. Values are marked in
accordance with IEC 62.
Aluminium Housed
Wirewound Resistors
WH Series
© 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
108
Issue D · 03.06
Welwyn Components
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: 1000 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
Pulse handling Data available by request
Performance Data
Dimensions (mm)
Type ABCEF
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
Type GHLMN
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
Physical Data
109
Aluminium Housed
Wirewound Resistors
WH Series
© 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 Issue D · 03.06
Welwyn Components
Application Notes
Reference aluminium heatsink dimension
CECC 40203-006 L W H Reference
cm cm cm area sq. cm
AA (WH5) 15.5 10 5 410
BA (WH10)
CA (WH25) 18 13 5 544
DA (WH50)
Aluminium thickness 1mm
WH50 only
To load at maximum commercial rating (50W) mount on heatsink 30.5cm x 30.5cm x 1.5mm.
Derating must be applied when resistors are mounted on a heat sink of smaller dimensions than defined in Graph 1.
It is recommended that the resistor base should be coated with heatsink compound before mounting to obtain the
stated operating characteristics.
The heatsink compound 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.
Reference chassis
LW
H
5 10
10
20
30
40
50
50 100 500 1000
Heatsink Surface Area (cm2)
Maximum Dissipation (Watts)
AA
BA
CA
DA
544cm2
410cm2
RATEDDISSIPATIONAT25C
RATED DISSIPATIONAT 70C
25C
25C
25C
70C
70C
70C
CECC 40 STYLE
Graph 1
Ordering Procedure
Example: WH25 at 3.3 kilohms and 5% tolerance in a box of 50 pieces –
W H 2 5 – 3 K 3 J I
Type
Value (use IEC62 code)
Tolerance (use IEC62 code)
F
1%
J
5%
G
2%
K
10%
Packing
I
Bulk
All sizes
50/box
Standard
For CECC released product state on order the CECC number and style. Example: WH25-3K3JI CECC40203-006 CA
For SnPb finish instead of Pb-free replace the packing suffix with PB. Example: WH25-3K3JPB
