Vitreous Enamelled
Wirewound Resistors Welwyn Components
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
Electrical Data
Commercial W21 W215 W22 W23 W24
Power rating at 25C watts 3.0 5.0 7.0 10.5 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 200C) pp/C Typically: <+-75 Maximum: +-200
BS CECC 40-201-002 Requirements Style JB HB KB LB MB
Power rating at 25C watts 2.9 5.0 7.0 10.5 14.0
Power rating at 70C 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 200C) ppm/C 5 ohms < 10 ohms: 400 10 ohms: 200
This table indicates the CECC specification requirements, and these are met or exceeded by the corresponding W20 series products
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
Physical Data
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
d
W22 22.0 8.0 23.1 0.8 2
D
L f
W23 38.0 8.0 - 0.8 3.5
W24 53.5 8.0 - 0.8 5
400
Construction
W21 W215 W23 W24
A high purity ceramic substrate is assembled with interference fit end caps to which are
W22
welded the termination wires. The resistive element is wound on the substrate and welded to
300
the caps; the vitreous enamel protective coating is then applied.
Terminations
200
Material Copper clad steel wire, nickel plated and solder-coated.
Strength The terminations meet the requirements of IEC 68.2.21.
100 Solderability The terminations meet the requirements of IEC 115-1, Clause 4.17.3.2.
Length W23s and W24s are not supplied on tape. Minimum lead length is 30 mm.
Marking
0
0 5 10 15 20 The resistors are legend marked with type reference, resistance value and tolerance. Values are
marked in accordance with IEC 62.
Dissipation Watts
General Note
Welwyn Components reserves the right to make changes in product specification without notice or liability.
A subsidiary of
All information is subject to Welwyns own data and is considered accurate at time of going to print.
TT electronics plc
Welwyn Components Limited Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0) 1670 822181 Facsimile: +44 (0) 1670 829465 Email: [email protected] Website: www.welwyn-tt.com
Temperature Rise C
Vitreous Enamelled
Wirewound Resistors
Welwyn Components
W20 Series
Flammability
Solvent Resistance
All materials used in the construction of W series resistors
The body protection and marking are resistant to all normal
are inorganic and inherently non burning.
industrial cleaning solvents suitable for printed circuits.
Performance Data
CECC 40201-002 Actual Performance
Requirements Maximum Typical
Load at commercial rating: 1000 hrs at 25c R% 5 3.5
Load at CECC rating: 1000 hours at 25c R% 5 5 3.5
Dry heat: 1000 hours at 200c R% 52 1
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) v/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
Application Notes
Packaging
The termination should not be bent closer than 1.6mm from For W21 and W215 the standard method of packaging is
the body, and the recommended minimum bend radius is taped in Ammo Packs. For W22 the standard method of
1.2mm. The terminations are solderable to within 4mm from packaging is taped and reeled. Alternatives available by
the body. When cold, vitreous enamel has excellent insulation special request are detailed in the table below. W23s and
resistance. In common with all insulants the specific resistance W24s are available only as loose packed in boxes. W series
of the enamel decreases with increase in temperature. resistors can be supplied preformed. Contact factory for
Therefore, resistors operated at near maximum temperature details.
cannot be classed as insulated and should not be used in
contact with any conducting material. Care must be taken
10
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. f f
1 2
6 b 6
f f 1.4 mm
1 2
116 Derating Curve
100
54
Type b
W21 632
W215 732
0
25 70 200 315
W22 732
Ambient temperature C
Welwyn Components Limited Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0) 1670 822181 Facsimile: +44 (0) 1670 829465 Email: [email protected] Website: www.welwyn-tt.com
% of Rated Power