Compact Flameproof Power
Wirewound Resistors Welwyn Components
WP-S Series
Small size for power rating
Enhanced pulse handling capability
Flameproof protection
SMD Z-form available
RoHS compliant with Pb-free terminations
Electrical Data
WP1S WP2S WP25S WP3S WP4S WP5S WP7S
Power rating at 25C watts 1 2 2.5 3 4 5 7
5s overload rating at 25C watts 5 10 12.5 15 20 25 35
Short pulse performance See Pulse Performance graphs
Resistance range ohms R068 to 430R R05 to 900R R05 to 900R R01 to 2K2 R01 to 10K R015 to 6K8 R15 to 10K
Limiting element voltage volts 50 50 75 100 100 150 150
TCR ppm/C <1R: 350 1R: 200
Isolation Voltage volts 250 350 500 700
Resistance Tolerance %
<20R: 5 20R: 1, 2, 5 <R10: 5 <20R: 5 20R: 1, 2, 5
R10: 1, 2, 5
Standard Values E24 preferred
Thermal Impedance C/watt 140 110 90 82 62 54 35
Ambient temperature range C -55 to +155
Physical Data
Dimensions (mm) & Weight (g)
Type L max D max f min d nom PCB Min Wt.
D
mount bend nom
centres radius
WP1S 6.2 2.8 21.20 0.6 10.20 0.6 0.22
WP2S 9.0 3.6 19.80 12.70 0.50
WP25S 12.5 4.5 17.80 18.40 0.50
WP3S 14.5 5.2 24.55 20.30 1.10
0.8
1.2
Lf
WP4S 13 5.6 22.75 18.90 1.00
d
WP5S 16.5 7.0 23.55 22.86 1.75
WP7S 25.0 8.8 28.30 31.40 4.40
Construction
A high purity ceramic substrate is assembled with interference fit end caps to which are welded the terminations. The resistive
element is wound on the substrate and welded to the caps. Flameproof silicone cement coating is applied prior to marking with
indelible ink. The components are then leadformed if required and packed.
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: info@welwyn-tt.com Website: www.welwyn-tt.com Issue D 04.06Compact Flameproof Power
Wirewound Resistors
Welwyn Components
WP-S Series
Terminations
Material: Hot tin dipped copper wire
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
Marking
WP1S, WP2S, WP25S and WP3S resistors R10 and above are marked with four colour bands in conformance with IEC62. Values
below R10 are marked with three bands (two digits indicating value in milliohms, and tolerance); there is no multiplier band.
WP4S, WP5S and WP7S resistors are legend marked with type reference, resistance value and tolerance.
Solvent Resistance
The body protection and marking are resistant to all normal industrial cleaning solvents suitable for printed circuits.
Flammability
The resistor coating will not burn or emit incandescent particles under any condition of applied temperature or power overload.
Performance Data
Maximum Typical Change
Load at rated power: 1000hrs @ 25C R% 5 +0.001 3
Dry heat: 1000hrs @ 200C R% 5 +0.001 3
Short term overload (5 x Pr for 5s) R% 5 +0.001 1
Derating from rated power @25C Zero at 280C
Climatic R% 5 +0.001 2
Climatic category 55/200/56
TRC & Vibration R% 5 +0.001 1
Robustness & solder heat R% 5 +0.001 1
Long term damp heat (56 days) R% 5 +0.001 1
Pulse Performance
The pulse energy capacity limits in the graph below relate to pulses below 100ms duration, low mean power dissipation and at
25C.
WP-S Short Pulse Energy Capacity
100
10
WP7S
WP5S
WP4S
1
WP3S
WP25S
WP2S
WP1S
0.1
10000
0.1 1 10 100 1000
Value (ohms)
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 04.06
Energy (joules)