Aluminium Housed
Wirewound Resistors
WH Series
• High power dissipation up to 300W
• All welded construction
• Suitable for severe environments
• Designed for excellent thermal conductivity to heatsink
• RoHS compliant
Electrical Data
WH5 WH10 WH25 WH50 Notes
Power rating at 25°C watts 10 15 25 50 * 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 <10R: ±75 ≥10R to <100R: ±50 ≥100R: ±25
Resistance tolerance % 1(F), 2(G), 5(J) and 10(K)
Low value limits ohms 1R at 1% 0R5 at 2% 0R05 at 5% 0R01 at 10% WH50 0R015 at 10%
Isolation voltage volts 1500 1500 3000 3000 DC or AC peak
* For load at maximum rating mount on aluminium heatsink 30.5 cm x 30.5 cm x 1.5 mm
CECC 40203-006 Requirements * AA BA CA DA Notes
Power rating at 25°C watts 10 15 25 40 On standard heatsink
Resistance range ohms 0R05 to 3K4 0R05 to 15K 0R05 to 33K 0R05 to 82K
TCR (-55° to 200°C) ppm/°C ≥5R to ≤10R: ± 100 >10R: ±50
Resistance tolerance % 1(F), 2(G), and 5(J)
Low value limits ohms 1R at 1% 0R5 at 2% 0R05 at 5%
Isolation voltage volts 1000 1000 2000 2000 DC or AC peak
* This table indicates the CECC specification requirements which are met or exceeded by the corresponding WH series products.
Limiting element voltage volts 150 250 500 1250 DC or AC rms
Standard values E24 preferred range Other values to order
Thermal impedance °C/watt 16.0 10.0 6.0 3.5 On standard heatsink
Ambient temperature range °C -55 to 200
WH100 WH200 WH300 Notes
Power rating at 25°C watts 100 200 300 On standard heatsink
Resistance range ohms 0R01 to 70K 0R01 to 50K 0R01 to 68K
TCR (-55° to 200°C) ppm/°C ≤1K0: ±100 >1K0: ±25
Resistance tolerance % Standard 5(J) and 10(K). also available : 1(F) and 2(G)
Low value limits ohms Typically ≥0R05: ±5% ≤0R047: ±10%
Isolation voltage volts 6360 7070 7070 DC or AC peak
Limiting element voltage volts 1900 1900 2500 DC or AC rms
Standard values
E24 preferred range Other values to order
Thermal impedance °C/watt 1 0.7 0.6 On standard heatsink
Ambient temperature range °C -55 to 200
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 test data and is considered accurate at time of print.
Welwyn Components Limited
Welwyn Electronics Park, Bedlington, Northumberland, NE22 7AA, England. Tel: 01670 822181 Fax: 01670 829465 Web: www.welwyn-tt.com
Aluminium Housed
Wirewound Resistors
Physical Data
Dimensions (mm) & Weight (g)
WH5 - 50 A B C E F G H L M N Dt Wt.
Type Max ±0.3 ±0.3 Min Max Max Dia ±0.2
Max ±0.5 Max Min Nom
WH5 30 12.4 11.3 1.9 17 9 2.4 17.0 4.3 1.8 2.5 3.6
WH10 36.5 15.9 14.3 1.9 21 11 2.4 21.0 5.2 2.2 2.9 5.6
WH25 51 19.8 18.3 2.8 28 15 3.3 29.0 7.2 2.6 4.3 13
WH50 72.5 21.4 39.7 2.8 30 16 3.3 51.0 7.9 2.6 5.1 29
WH100 – 300
A
Max B
Max C
Max D
Max E
Max F
±0.3 G
±0.3 H
Max J
Max K
Max L
Nom*
M
Max Dt
Min Wt.
Nom
WH100 47.5 88 24.1 27.3 65.2 35 37 11.8 15.4 3.7 4.4 - 7.0 115
WH200 72.5 145.7 41.8 45.5 89.7 70 57.2 20.5 10.4 5.5 5.1 103.4 15 475
WH300 72.5 184.4 41.8 45.5 127.7 104 59 20.5 12.4 5.5 6.6 141.4 15 700
* WH100: ±0.25, WH200 & WH300: ±0.45
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 test data and is considered accurate at time of print.
Welwyn Components Limited
Welwyn Electronics Park, Bedlington, Northumberland, NE22 7AA, England. Tel: 01670 822181 Fax: 01670 829465 Web: www.welwyn-tt.com
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 aluminium housing to give
optimum stability and reliability.
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
End face tracking distance = Dt
WH100
WH200 & 300
WH5
-
50
Aluminium Housed
Wirewound Resistors
Performance Data WH5 - 50 WH100 - 300
Actual
CECC 40203-006
Requirements Maximum Typical Maximum
Load at commercial rating: 1000hrs at 25°C ΔR% 1 1 0.4 2
Load at CECC rating: 1000hrs at 25°C ΔR% 1 1 0.4 N/A
Dry heat: 1000hrs at 200°C ΔR% 1 1 0.4 2
Derating from 25°C Zero at 200°C, see derating graph
Short-term overload ΔR% 1 1 0.2
Climatic sequence ΔR% 1 1 0.4
Climatic category 55/200/56
Long-term damp heat ΔR% 1 0.5 0.2
Temperature rapid change ΔR% 0.25 0.25 0.1 0.25
Resistance to solder heat ΔR% 0.25 0.25 0.05 WH100: 0.5
Vibration and bump ΔR% 0.25 0.25 0.025
Noise (in decade of frequency) μV/V Not specified 0 0 0
Insulation resistance ohms 1G min 10G min
Pulse and overload performance Not specified See graphs
Note: A 0.05 ohm addition is to be added to the performance of all resistors < 10 ohms.
Application Notes
After soldering care should be taken to ensure that there are no flux residues on the end faces of the moulding
compound, otherwise insulation resistance will be reduced. The minimum surface tracking distances from termination
to casing are shown in the Physical Data tables as dimension Dt.
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.
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 test data and is considered accurate at time of print.
Welwyn Components Limited
Welwyn Electronics Park, Bedlington, Northumberland, NE22 7AA, England. Tel: 01670 822181 Fax: 01670 829465 Web: www.welwyn-tt.com
1
10
0.1 1 10 100 1000
Overload Duration (s)
Multiple of Rated Power
WH5&10
WH100-300
WH25-300
WH5-50
0.1
1
10
100
1000
10000
0.01 0.1 1 10 100 1000 10000100000
Value (ohms)
Energy (joules)
WH5
WH10
WH25
WH50
WH100
WH200
WH300
Pulse and Overload Performance
For short durations of ≤0.1s the energy graph should
be used. For longer durations the overload graph
applies.
Terminations
WH5-100
Material Pb-free solder dipped, copper clad steel
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
WH200 & 300
Material M6 threaded steel terminal
Strength Termination robustness 50N
Solderability Non-solderable
Aluminium Housed
Wirewound Resistors
The standard aluminium heatsinks are defined in the table below. If smaller heatsinks are used then derating should
be applied as indicated in the graph below.
WH200 and WH300 are supplied with a set of four M6 nuts and washers. The screw terminations can support a
maximum tightening torque of 5Nm.
Packaging
WH5-100 resistors are packed in plastic bags and boxed. WH200 & 300 are individually boxed.
Ordering Procedure
Example: WH25 at 100 ohms with a 5% tolerance:
W H 2 5 – 1 0 0 R J I
Type
Value (use IEC62 code)
Tolerance (use IEC62 code)
F 1% J 5%
G 2% K 10%
Packing
I Bulk All Sizes Standard
The following options apply to WH5 – 50 only:
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
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 test data and is considered accurate at time of print.
Welwyn Components Limited
Welwyn Electronics Park, Bedlington, Northumberland, NE22 7AA, England. Tel: 01670 822181 Fax: 01670 829465 Web: www.welwyn-tt.com
Type (CECC) Thickness (mm)
Area (cm²)
WH5 (AA) 1 410
WH10 (BA) 1 410
WH25 (CA) 1 544
WH50 (DA) 1 544
WH50 @ 50W 1.5 930
WH100 3 1000
WH200 3 3800
WH300 3 5800
Reference heatsink dimension
s
1
10
100
1000
1 10 100 1000 10000
Heatsink Surface Area (cm
2
)
Max imum D is s ipation (W)
WH10/BA 70
°C
WH10/BA 25
°C
WH5/AA 70
°C
WH5/AA 25
°C
WH25/CA 70
°C
WH25/CA 25
°C
DA 70
°C
DA 25
°C
WH50 25
°C
WH100 70
°C
WH100 25
°C
WH200 70°C
WH200 25
°C
WH300 70
°C
WH300 25
°C
0
20
40
60
80
100
120
0 100 200
Ambient Temperature (°C)
Proportion of Pr (%)
Derating for reduced heatsink dimensions
Derating for ambient temperature
