Compact Flameproof Power
Wirewound Resistors
WP-S Series
Welwyn Components
•
•
•
•
•
Small size for power rating
Enhanced pulse handling capability
Flameproof protection
SMD Z-form available
RoHS compliant with Pb-free terminations
Electrical Data
WP1S
Power rating at 25°C
5s overload rating at 25ºC
Short pulse performance
Resistance range
Limiting element voltage
TCR
Isolation Voltage
Resistance Tolerance
Standard Values
Thermal Impedance
Ambient temperature range
°C/watt
°C
140
110
90
ohms
volts
ppm/°C
volts
%
250
<20R: 5
≥20R:
1, 2, 5
E24 preferred
82
-55 to +155
62
54
35
R068 to 430R
50
R05 to 900R
50
watts
watts
1
5
WP2S
2
10
WP25S
2.5
12.5
WP3S
3
15
WP4S
4
20
WP5S
5
25
WP7S
7
35
See Pulse Performance graphs
R05 to 900R R01 to 2K2
75
<1R: 350
350
100
≥1R:
200
500
<R10: 5
≥R10:
1, 2, 5
<20R: 5
700
≥20R:
1, 2, 5
R01 to 10K
100
R015 to 6K8 R15 to 10K
150
150
Physical Data
Dimensions (mm) & Weight (g)
Type
L max
D max
f min
d nom
PCB
mount
centres
10.20
12.70
18.40
20.30
0.8
18.90
22.86
31.40
1.2
Min
bend
radius
0.6
Wt.
nom
0.22
0.50
0.50
1.10
1.00
1.75
4.40
D
WP1S
WP2S
WP25S
WP3S
WP4S
WP5S
WP7S
6.2
9.0
12.5
14.5
13
16.5
25.0
2.8
3.6
4.5
5.2
5.6
7.0
8.8
21.20
19.80
17.80
24.55
22.75
23.55
28.30
0.6
d
L
f
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.
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 E · 07.06
© 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
Compact Flameproof Power
Wirewound Resistors
WP-S Series
Welwyn Components
Terminations
Material:
Strength:
Solderability:
Hot tin dipped copper wire
The terminations meet the requirements of IEC 68.2.21
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
Load at rated power: 1000hrs @ 25°C
Dry heat: 1000hrs @ 200°C
Short term overload (5 x Pr for 5s)
Derating from rated power @25°C
Climatic
Climatic category
TRC & Vibration
Robustness & solder heat
Long term damp heat (56 days)
Typical Change
3
3
1
Zero at 280°C
2
55/200/56
1
1
1
∆
R%
∆
R%
∆
R%
∆
R%
∆
R%
∆
R%
∆
R%
5 +0.001Ω
5 +0.001Ω
5 +0.001Ω
5 +0.001Ω
5 +0.001Ω
5 +0.001Ω
5 +0.001Ω
Pulse Performance
The pulse energy capacity limits in the graph below relate to pulses below 100ms duration, low mean power dissipation and at
25ºC.
WP-S Short Pulse Energy Capacity
100
Energy (joules)
10
WP5S
WP7S
1
WP25S
WP2S
WP4S
WP3S
0.1
0.1
1
10
100
Value (ohms)
WP1S
1000
10000
© 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
Compact Flameproof Power
Wirewound Resistors
WP-S Series
Welwyn Components
Application Notes
1. If the resistors are to dissipate full rated power, it is recommended that the terminations should not be soldered closer than
4mm from the body.
2. Due to operating temperature limits imposed by some PCB materials, derating may be necessary. An estimate of the
temperature rise to be expected at the center of the body can be calculated using the thermal impedance figures given under
Electrical Data.
3. WP-S resistors can also be supplied with radial, goalpost or lancet pre-formed leads. WP2S, WP3S, WP4S and WP5S are also
available in an SMD format with Z formed leads and packed in blister tape. Consult factory for details.
Radial
Goalpost
Lancet
Z-form
Packaging
The standard packaging for WP-S is taped. The critical dimensions are shown in Figure 1. The component wires will not
protrude beyond the outside edge of the tapes. Taped product is then packed into boxes or onto reels; see Ordering Procedure
for details. Alternative packaging is available by request. Pre-formed resistors are supplied loose packed in plastic bags or boxes.
Figure 1
Dimensions (mm)
WP1S
WP2S
WP25S
WP3S
WP4S
WP5S
WP7S
b
52
52
52
67
63
63
85
c
5
5
5
10
10
10
10
C
f1
6
b
f2
6
Body location f1 - f2 < 1.4mm
© 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
Compact Flameproof Power
Wirewound Resistors
WP-S Series
Welwyn Components
Ordering Procedure
Example: WP2S at 680 ohms and 5% tolerance in ammo pack box of 2500 pieces -
Type
Value (use IEC 62 code)
Tolerance (use IEC 62 code)
F
G
J
1%
2%
5%
WP2S
–
680R
J
A25
Packing
A5
A25
A15
A1
A1
T07
Tape
Ammo
WP1S
WP2S
WP25S
WP3S
WP4S
WP5S
WP7S
5000/box
2500/box
1500/box
1000/box
1000/box
750/reel
700/reel
Standard
© 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
