Aluminium Housed
Wirewound Resistors
WH Series
Welwyn Components
•
High power dissipation for size
•
All welded construction
•
Suitable for severe environments
•
Designed for excellent thermal
conductivity to heatsink
Electrical Data
WH5
Power rating at 25°C
Resistance range
TCR (-55° to 200°C)
Resistance tolerance
Low value limits
watts
ohms
ppm/°C
%
ohms
1 at 1%
AA
10
0.05 to 3.4k
10
0R01 to 10K
<10Ω : ±75
WH10
15
0R01 to 20K
≥
to <100 : ±50
1, 2, 5, 10
0.5 at 2%
BA
15
0.05 to 15k
≥5Ω ≤
10Ω ± 100
1, 2, 5
1 at 1%
150
16.0
250
10.0
-55 to 200
0.5 at 2%
0.05 at 5%
500
6.0
1250
Other values to special order
3.5
Mounted on standard heatsink
WH50 0.015 at 10%
0.05 at 5%
CA
25
0.05 to 33k
>10Ω ± 50
0.01 at 10%
DA
40
0.05 to 82k
Mounted on standard heatsink
WH50 0.015 at 10%
WH25
25
0R01 to 44K
≥100Ω
: ±25
WH50
50*
0R015 to 120K
Notes
Mounted on standard heatsink
Approved CECC 40203 - 006
Power rating at 25°C
Resistance range
TCR (-55° to 200°C)
Resistance tolerance
Low value limits
Limiting element voltage
Standard values
Thermal impedance
°C/watt
°C
Ambient temperature range
watts
ohms
ppm/°C
%
ohms
volts
E24 preferred range
*For load at maximum rating mount on heatsink 30.5 cm x 30.5 cm x 1.5 mm
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.
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.
Terminations
Material
Strength
Solderability
Solder dipped, copper clad steel 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
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 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
107
Aluminium Housed
Wirewound Resistors
WH Series
Welwyn Components
Physical Data
Dimensions (mm)
Type
WH5
WH10
WH25
WH50
Type
WH5
WH10
WH25
WH50
A
Max
30.0
36.5
51.0
72.5
G
Max
9
11
15
16
B
±0.3
12.4
15.9
19.8
21.4
H
Dia ±0.2
2.4
2.4
3.3
3.3
C
±0.3
11.3
14.3
18.3
39.7
L
Max
17.0
21.0
29.0
51.0
E
Min
1.9
1.9
2.8
2.8
M
±0.5
4.3
5.2
7.2
7.9
F
Max
17
21
28
30
N
Max
1.8
2.2
2.6
2.6
Performance Data
CECC
40203-006
Load at commercial rating: 1000 hrs at 25°C
Load at CECC rating: 1000 hours at 25°C
Dry heat: 1000 hours at 200°C
Derating from 25°C
Short term overload
Climatic sequence
Climatic category
Long term damp heat
Temperature rapid change
Resistance to solder heat
Vibration and bump
Noise (in decade of frequency)
Insulation resistance.
Isolation voltage : WH5 and 10
: WH25 and 50
Pulse handling
∆R
%
∆R
%
∆R
%
∆R
%
µV/V
ohms
volts AC peak
volts AC peak
∆R
%
∆R
%
∆R
%
∆R
%
∆R
%
1.0
1.0
1.0
Zero at 200°C
1.0
1.0
55/200/56
1.0
0.25
0.25
0.25
Not specified
>1Gohm
1000 min
2000 min
0.5
0.25
0.25
0.25
zero
>20Tohm
1500 min
3000 min
Data available by request
0.2
0.1
0.05
0-.025
zero
>100Gohm
See application
notes
1.0
1.0
0.2
0.4
1.0
1.0
1.0
Actual
Maximum
Typical
0.4
0.4
0.4
Notes
© 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
Aluminium Housed
Wirewound Resistors
WH Series
Welwyn Components
Application Notes
Reference aluminium heatsink dimension
CECC 40203-006
AA (WH5)
BA (WH10)
CA (WH25)
DA (WH50)
L
cm
15.5
18
W
cm
10
13
H
cm
5
5
Reference
area sq. cm
Maximum Dissipation (Watts)
Graph 1
50
40
30
20
10
5C
T2
544cm
2
NA
IO
AT
IP
70C
ISS
AT
ON
DD
ATI
TE
SIP
RA
25C
DIS
ED
RAT
70C
25 C
70C
25C
70C
CECC 40 STYLE
410
544
DA
Aluminium thickness 1mm
CA
BA
AA
Reference chassis
410cm
2
5 10
50 100
2
500 1000
H
L
Heatsink Surface Area (cm )
W
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.
Ordering Procedure
Example: WH25 at 3.3 kilohms and 5% tolerance in a box of 50 pieces
–
WH25
–
3K3J
I
Type
Value (use IEC62 code)
Tolerance (use IEC62 code)
F
G
1%
2%
J
K
5%
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
© 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
109
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