Fast Fusible Metal

Film Resistors

WFF Series

© 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 · 03.06

Welwyn Components

162

Test Method (for graph 3 and 4)

The resistor is subject to 10,000 pulses as shown in figure

(1). Maximum resistance change due to test will not

exceed 1%. Maximum pulse voltages are detailed in graph

3 above.

For any combination of power and pulse length (ti). tp is

determined by the need to ensure that the average power

does not exceed the rated power.

tp =

Applied Pulse Power

Rated Power

x ti

100000

10000

1000

100

10

10

100

1000

10000

1.2/50

μS Pulse Withstand

Value (OHMS)

WFF 1/4

WFF 1/2

WFF 1

Graph 1

100000

10000

1000

100

10

10

100

1000

10000

10/700

μS Pulse Withstand

Value (OHMS)

WFF 1/4

WFF 1/2

WFF 1

Graph 2

1.0000

0.1000

0.0100

0.0010

0.0001

100

1000

10000

Maximum peak pulse voltage

as a function of pulse duration (ti)

WFF 1/4

WFF 1/2

WFF 1

ti (s)

Graph 3

0

1

10

100

Maximum peak pulse power

as a function of pulse duration (ti)

WFF 1/4

WFF 1/2

WFF 1

ti (s)

1.0000

0.1000

0.0100

0.0010

0.0001

Graph 4

Above tests carried out in accordance with IEC 115.1. Change of value after test ±1%

Time (secs)

tp

ti

Figure 1

Pulse Handling Graphs

Maximum

Load: 1000 hrs at 70˚ C

3

%

R

Shelf life: 12 months at room temperature

2

%

R

Derating from rated power at 70˚

5

5

1

t

a

o

r

e

z

C

˚C

Temperature rapid change

5

.

0

%

R

Resistance to solder heat

5

.

0

%

R

Performance Data

Issue E · 01.07

OBSOLETE