Compact Flameproof Power
Wirewound Resistors
WP-S Series
Welwyn Components
Performance Data
Maximum Typical Change
Load at rated power: 1000hrs @ 25°C ∆R% 5 +0.001Ω 3
Dry heat: 1000hrs @ 200°C ∆R% 5 +0.001Ω 3
Short term overload (5 x Pr for 5s) ∆R% 5 +0.001Ω 1
Derating from rated power @25°C Zero at 280°C
Climatic ∆R% 5 +0.001Ω 2
Climatic category 55/200/56
TRC & Vibration ∆R% 5 +0.001Ω 1
Robustness & solder heat ∆R% 5 +0.001Ω 1
Long term damp heat (56 days)
∆R% 5 +0.001Ω 1
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
Terminations
WP1S, WP2S, WP25S and WP3S resistors R10 and above are marked with four or five 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.
Marking
The body protection and marking are resistant to all normal industrial cleaning solvents suitable for printed circuits.
Solvent Resistance
The resistor coating will not burn or emit incandescent particles under any condition of applied temperature or power overload.
Flammability
The pulse energy capacity limits in the graph below relate to pulses below 100ms duration, low mean power dissipation and at
25ºC.
Pulse Performance
© 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 E · 07.06
100
WP-S Short Pulse Energy Capacity
Value (ohms)
10
1
0.1
0.1 1 10 100 1000
10000
Energy (joules)
WP7S
WP5S
WP4S
WP3S
WP2S
WP1S
WP25S
