AC01 datasheet(5/24 Pages) PHILIPS

5 / 24 page

2000 Oct 20

BCcomponents

Product specification

Cemented wirewound resistors

AC01/03/04/05/07/10/15/20

PULSE LOADING CAPABILITIES

How to generate the maximum allowed pulse-load from the graphs composed for wirewound resistors of the AC-types.

Single pulse condition; see Fig.3

1. If the applied pulse energy in Joules or Wattseconds is

known and also the R-value to be used in the

application; take the R-value on the X-axis and go

vertically to the curved line. From this point go

horizontally to the Y-axis, this point gives the maimum

allowed pulse energy in Joules/ohm or Wattsec./ohm.

By multiplying this figure with -value in use gives the

maximum allowed pulse-energy in Joules or Wattsec. If

this figure is higher than the applied pulse-energy the

application is allowed. Otherwise take one of the other

graphs belonging to AC-types with higher Pn.

2. If, contrary to the information above, the applied

peak-voltage and impulse times ti are known. Calculate

the pulse-energy (Ep) in Joules or Wattsec. by the use of

the following formula:

(Vp = peak voltage; ti =impulse-time)

By dividing this result with the Rn-value of the R in use,

gives the value Wattsec./ohm on the Y-axis. Draw a line

horizontally to the curved line and at the intersection

the vertical line to the X-axis gives the maximum

allowed Rn-value to be used in the application. If this

Rn-value is higher than the R-value to be used in the

application, the application is allowed. If not, take one

of the other graphs belonging to AC-types with higher Pn

or change the Rn-value to be used.

Repetitive pulse condition; see Fig.2

With these graphs we can determine the allowed

pulse-energy in Watts depending on the impulse- time ti and

the repetition time tp of the pulses. The parameter is the

Resistance Value. If the pulse shape is known (impulse-time

ti and repetition time tp), draw a line vertically from the

X-axis at the mentioned ti to the line of the involved R-value.

From the intersection the horizontal line to the Y- axis

indicates the maximum allowed pulse-load at a certain tp/ti.

If the vertical line from the X-axis crosses the applied tp/ti

before reaching the R-line, this tp/ti line gives the maximum

allowed pulse-energy at the Y-axis. If the applied

pulse-energy is known (in Watts) and the impulse-time ti

also, draw a line horizontally from the Y-axis to the crossing

with the pulse-line (ti) and find the possible R-value needed

in this application. The horizontal tp/ti lines give the

maximum allowed pulse-load till they reach the R-line, that

point indicates the maximum allowed impulse-time ti at the

horizontal axis.

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