Vitreous Enamelled
Wirewound Resistors
W20 Series
Welwyn Components
•
CECC approved
•
Suitable for harsh environments
•
Impervious lead free vitreous enamel coating
•
Overload characteristics ideal
for protection circuits
•
•
High stability and reliability
High power dissipation for size
Electrical Data
Commercial
Power rating at 25°C
Resistance range at 1% tolerance
2% tolerance
5% tolerance
TCR (-55° to 200°C)
Approved BS CECC 40-201-002
Power rating at 25°C
Power rating at 70°C
Resistance range at 1% tolerance
2% tolerance
5% tolerance
TCR (-55° to 200°C)
Applicable to commercial and approved ranges
Limiting element voltage
Standard values
Thermal impedance
Ambient temperature range
watts
ohms
ohms
ohms
pp/°C
Style
watts
watts
ohms
ohms
ohms
ppm/°C
W21
3.0
1R to 10K
0R5 to 10K
0R1 to 10K
W215
W22
W23
W24
5.0
7.0
10.0
14.0
1R to 15K
1R to 22K
1R to 60K 1R to 100K
0R5 to 15K 0R5 to 22K 1R to 60K 1R to 100K
0R1 to 15K 0R1 to 22K 0R15 to 60K 0R2 to 100K
Typically: <+75
Maximum: +200
JB
HB
KB
LB
MB
2.9
5.0
7.0
10.0
14.0
2.5
4.3
6.0
9.0
12.0
1R to 10K
1R to 15K
1R to 20K
1R to 56K 1R to 100K
0R5 to 10K 0R5 to 15K 0R5 to 20K 1R to 56K 1R to 100K
0R1 to 10K 0R1 to 15K 0R1 to 20K 0R15 to 56K 0R2 to 100K
≥5
ohms < 10 ohms: ±400
≥10
ohms: ±200
volts
°C/watt
°C
100
88
160
200
500
E24 preferred. Other values to special order
58
44
29
-55 to 200
750
22
Physical Data
Dimensions
Type
W21
W215
W22
W23
W24
400
(mm) and Weight (g)
L max
D max
12.7
5.6
22.0
7.0
22.0
8.0
38.0
8.0
53.5
8.0
W215
W22
W23
W24
f min
22.75
23.1
23.1
-
-
d nom
0.8
0.8
0.8
0.8
0.8
Wt.nom
1
2
2
3.5
5
d
D
L
f
Temperature Rise
°C
W21
Construction
A high purity ceramic substrate is assembled with interference fit end caps to which are
welded the termination wires. The resistive element is wound on the substrate and welded to
the caps; the vitreous enamel protective coating is then applied.
300
200
Terminations
Material
Strength
Solderability
Length
100
Copper clad steel wire, nickel plated and solder-coated.
The terminations meet the requirements of IEC 68.2.21.
The terminations meet the requirements of IEC 115-1,– Clause 4.17.3.2.
W23’s and W24’s are not supplied on tape. Minimum lead length is 30 mm.
0
0
5
10
15
20
Marking
Dissipation – Watts
The resistors are legend marked with type reference, resistance value and tolerance. Values are
marked in accordance with IEC 62.
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 C · 04.03
© 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
85
Vitreous Enamelled
Wirewound Resistors
W20 Series
Solvent Resistance
The body protection and marking are resistant to all normal
industrial cleaning solvents suitable for printed circuits.
Welwyn Components
Flammability
All materials used in the construction of ‘W’ series resistors
are inorganic and inherently non burning.
Performance Data
CECC 40201-002
Requirements
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
Shelf life: 12 months at room temperature
Derating
Short term overload
Climatic
Climatic category
Long term damp heat
Temperature rapid change
Resistance to solder heat
Vibration and bump
Noise (in decade of frequency)
Robustness
Insulation resistance
Voltage Proof
Pulse handling
∆R%
∆R%
∆R%
∆R%
∆R%
∆R%
∆R%
∆R%
∆R%
∆R%
∆R%
µv/v
∆R%
ohms
volts
5
5
not specified
1
5
55/200/56
5
1
1
1
not specified
1
not specified
not specified
Actual Performance
Maximum
Typical
5
3.5
5
3.5
2
1
0.03
0.02
see derating curve
1.0
0.2
0.5
0.2
0.05
0.02
0.5
0.2
0.25
0.03
0.25
0.05
zero
zero
0.4
0.05
>.1G ohm
>.1G ohm
500 min
500 min
data available by request
Application Notes
The termination should not be bent closer than 1.6mm from
the body, and the recommended minimum bend radius is
1.2mm. The terminations are solderable to within 4mm from
the body. When cold, vitreous enamel has excellent insulation
resistance. In common with all insulants the specific resistance
of the enamel decreases with increase in temperature.
Therefore, resistors operated at near maximum temperature
cannot be classed as insulated and should not be used in
contact with any conducting material. Care must be taken
when determining clearance distance between the resistor
body and the printed circuit board or other components to
ensure these are not over heated. Resistance is measured
6mm from body.
116
Packaging
For W21 and W215 the standard method of packaging is
taped in Ammo Packs. For W22 the standard method of
packaging is taped and reeled. Alternatives available by
special request are detailed in the table below. W23’s and
W24’s are available only as loose packed in boxes. W series
resistors can be supplied preformed. Contact factory for
details.
10
f
1
6
f
2
b
f
1
– f
2
≤
1.4 mm
6
Derating Curve
% of Rated Power
100
Standard Quantities Per Package
54
Type
Ammo pack
Reel
Small box
25
70
200
315
W21
1000
1000
n/a
b
63±2
73±2
73±2
W215
750
750
n/a
W22
500
700
n/a
W23
n/a
n/a
50
W24
n/a
n/a
25
0
Ambient temperature
°C
Type
W21
W215
W22
© 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
86
Issue C · 04.03
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