B32671L datasheet(18/31 Pages) EPCOS

18 / 31 page

Operation at overvoltages during heating and ignition of lamps (TA

≤40 °C)

In lighting applications, the capacitors can be subjected to overvoltages during the heating and ig-

nition periods. An overvoltage occurs when the operation voltage exceeds the permissible

AC voltage at the resonant frequency fr.

For a repetitive application of on/off switching pulses (as for example in the life tests applied by

electronic ballast manufacturers), limits have to be imposed on the time periods under overvolt-

age and on the duty cycle, in order to keep the capacitance value within the required margins:

The overvoltage time tOV should be less than 1 sec.

The maximum duty cycle of the overvoltage is given by

where VRMS,ov is the RMS voltage during period tOV

and VRMS is the permissible AC voltage for continuous operation at the resonant frequency fr

(given by the “permissible AC voltage versus frequency f” graphics in theprevious pages).

The drift of capacitance depends on the Vpp attained, and the total time under overvoltage,

which is calculated in hours as follows:

(Ni tOV) / 3600

where Ni is the number of overvoltage impulses and tOV is expressed in seconds.

The maximum drift of capacitance as a function of both parameters is provided graphically in the

following pages.

B32671L ... B32672L

High V AC, high temperature (wound)

Page 18 of 31

Please read Cautions and warnings and

Important notes at the end of this document.

B32671L 데이터시트(PDF) 18 Page - EPCOS