TT electronics WP1S, WP2S, WP25S, WP3S, WP4S Technical data

Compact Flameproof Power
Wirewound Resistors

WP-S Series

• Small size for power rating

• Enhanced pulse handling capability

• Flameproof protection

• SMD Z-form available

• RoHS compliant with Pb-free terminations

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: [phone] · Facsimile: [phone] · Email: [e-mail] · Website: www.welwyn-tt.com

Issue D · 04.06

A subsidiary of

TT electronics plc

Welwyn Components

Dimensions (mm) & Weight (g)

Type L max D max f min d nom PCB Min Wt.

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

WP4S 13 5.6 22.75 18.90 1.00

WP5S 16.5 7.0 23.55 22.86 1.75

WP7S 25.0 8.8 28.30 31.40 4.40

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.

Electrical Data

Physical Data

Construction

WP1S WP2S WP25S WP3S WP4S WP5S WP7S

Power rating at 25°C watts 1 2 2.5 3 4 5 7

5s overload rating at 25ºC 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 %

Standard Values E24 preferred

Thermal Impedance °C/watt 140 110 90 82 62 54 35

Ambient temperature range °C -55 to +155

<20R: 5 ≥20R: 1, 2, 5

<20R: 5 ≥20R: 1, 2, 5

<R10: 5

≥R10: 1, 2, 5

0.8

1.2

D

d

Lf

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 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: [phone] · Facsimile: [phone] · Email: [e-mail] · Website: www.welwyn-tt.com

Issue D · 04.06

WP-S Short Pulse Energy Capacity

100

10

1

Energy (joules)

0.1

WP2S

WP1S

0.1 1 10 100 1000

Value (ohms)

WP5S

WP25S

WP7S

WP4S

WP3S

10000

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.

Application Notes

Radial Goalpost Lancet Z-form

Compact Flameproof Power
Wirewound Resistors

WP-S Series

Welwyn Components

© Welwyn Components Limited Bedlington, Northumberland NE22 7AA, UK

Telephone: [phone] · Facsimile: [phone] · Email: [e-mail] · Website: www.welwyn-tt.com

Issue D · 04.06

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.

Packaging

Dimensions (mm) b c

WP1S 52 5

WP2S 52 5

WP25S 52 5

WP3S 67 10

WP4S 63 10

WP5S 63 10

WP7S 85 10

Figure 1

C

f1 f2

66

Body location f1 - f2 1.4mm

b

<

Compact Flameproof Power
Wirewound Resistors

WP-S Series

Welwyn Components

Example: WP2S at 680 ohms and 5% tolerance in ammo pack box of 2500 pieces -

Ordering Procedure

© Welwyn Components Limited Bedlington, Northumberland NE22 7AA, UK

Telephone: [phone] · Facsimile: [phone] · Email: [e-mail] · Website: www.welwyn-tt.com

Issue D · 04.06

Type WP2S – 680R J A25

Value (use IEC 62 code)

Tolerance (use IEC 62 code)

Packing

F1%

G2%

J5%

A5 WP1S 5000/box

A25 WP2S 2500/box

A15 Ammo WP25S 1500/box

A1 WP3S 1000/box Standard

A2 WP4S 2000/box

T07 Tape WP5S 750/reel

WP7S 700/reel