Vitreous Enamelled
Wirewound Resistors
W20 Series
•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
Dimensions (mm) and Weight (g)
Type L max D max f min d nom Wt.nom
W21 12.7 5.6 22.75 0.8 1
W215 22.0 7.0 23.1 0.8 2
W22 22.0 8.0 23.1 0.8 2
W23 38.0 8.0 - 0.8 3.5
W24 53.5 8.0 - 0.8 5
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
Commercial W21 W215 W22 W23 W24
Power rating at 25°C watts 3.0 5.0 7.0 10.0 14.0
Resistance range at 1% tolerance ohms 1R to 10K 1R to 15K 1R to 22K 1R to 60K 1R to 100K
2% tolerance ohms 0R5 to 10K 0R5 to 15K 0R5 to 22K 1R to 60K 1R to 100K
5% tolerance ohms 0R1 to 10K 0R1 to 15K 0R1 to 22K 0R15 to 60K 0R2 to 100K
TCR (-55° to 200°C) pp/°C Typically: <+75 Maximum: +200
Approved BS CECC 40-201-002 Style JB HB KB LB MB
Power rating at 25°C watts 2.9 5.0 7.0 10.0 14.0
Power rating at 70°C watts 2.5 4.3 6.0 9.0 12.0
Resistance range at 1% tolerance ohms 1R to 10K 1R to 15K 1R to 20K 1R to 56K 1R to 100K
2% tolerance ohms 0R5 to 10K 0R5 to 15K 0R5 to 20K 1R to 56K 1R to 100K
5% tolerance ohms 0R1 to 10K 0R1 to 15K 0R1 to 20K 0R15 to 56K 0R2 to 100K
TCR (-55° to 200°C) ppm/°C ≥5 ohms < 10 ohms: ±400 ≥10 ohms: ±200
Applicable to commercial and approved ranges
Limiting element voltage volts 100 160 200 500 750
Standard values E24 preferred. Other values to special order
Thermal impedance °C/watt 88 58 44 29 22
Ambient temperature range °C -55 to 200
Electrical Data
Physical Data
Issue C · 04.03
A subsidiary of
TT electronics plc
Welwyn Components
85
L
Df
d
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.
Terminations
Material Copper clad steel wire, nickel plated and solder-coated.
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.
Length W23’s and W24’s are not supplied on tape. Minimum lead length is 30 mm.
Marking
The resistors are legend marked with type reference, resistance value and tolerance. Values are
marked in accordance with IEC 62.
0 5 10 15 20
W21 W215
W22
W24
W23
400
300
200
100
0
Dissipation – Watts
Temperature Rise °C
W20_C.qxd 28/4/03 10:19 am Page 1
Vitreous Enamelled
Wirewound Resistors
W20 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
86
Issue C · 04.03
Welwyn Components
CECC 40201-002 Actual Performance
Requirements Maximum Typical
Load at commercial rating: 1000 hrs at 25°c ∆R% 5 3.5
Load at CECC rating: 1000 hours at 25°c ∆R% 5 5 3.5
Dry heat: 1000 hours at 200°c ∆R%521
Shelf life: 12 months at room temperature ∆R% not specified 0.03 0.02
Derating see derating curve
Short term overload ∆R% 1 1.0 0.2
Climatic ∆R% 5 0.5 0.2
Climatic category ∆R% 55/200/56
Long term damp heat ∆R% 5 0.05 0.02
Temperature rapid change ∆R% 1 0.5 0.2
Resistance to solder heat ∆R% 1 0.25 0.03
Vibration and bump ∆R% 1 0.25 0.05
Noise (in decade of frequency) µv/v not specified zero zero
Robustness ∆R% 1 0.4 0.05
Insulation resistance ohms not specified >.1G ohm >.1G ohm
Voltage Proof volts not specified 500 min 500 min
Pulse handling data available by request
Performance Data
Flammability
All materials used in the construction of ‘W’ series resistors
are inorganic and inherently non burning.
b
f1f2
66
10
f1 – f2 ≤ 1.4 mm
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.
Type W21 W215 W22 W23 W24
Ammo pack
1000 750 500 n/a n/a
Reel 1000 750 700 n/a n/a
Small box n/a n/a n/a 50 25
Standard Quantities Per Package
25 70 200 315
116
100
54
0
Ambient temperature °C
Derating Curve
% of Rated Power
Type b
W21 63±2
W215 73±2
W22 73±2
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.
Solvent Resistance
The body protection and marking are resistant to all normal
industrial cleaning solvents suitable for printed circuits.
W20_C.qxd 28/4/03 10:19 am Page 2
