MAY 2013

1.2.4 Effect of surges

The solid Tantalum capacitor has a limited ability to withstand

surges (15% to 30% of rated voltage). This is in common

with all other electrolytic capacitors and is due to the fact that

they operate under very high electrical stress within the oxide

layer. In the case of ‘solid’ electrolytic capacitors this is further

complicated by the limited self healing ability of the manganese

dioxide semiconductor.

It is important to ensure that the voltage across the terminals of

the capacitor does not exceed the surge voltage rating at any

time. This is particularly so in low impedance circuits where the

capacitor is likely to be subjected to the full impact of surges,

especially in low inductance applications. Even an extremely

short duration spike is likely to cause damage. In such situa-

tions it will be necessary to use a higher voltage rating.

1.2.5 Reverse voltage and non-polar operation

The reverse voltage ratings are designed to cover exceptional

conditions of small level excursions into incorrect polarity.

The values quoted are not intended to cover continuous

reverse operation.

The peak reverse voltage applied to the capacitor must not

exceed:

10% of rated DC working voltage to a maximum of

1V at 25°C

3% of rated DC working voltage to a maximum of

0.5V at 85°C

1% of category DC working voltage to a maximum of

0.1V at 125°C

1.2.6 Non-polar operation

If the higher reverse voltages are essential, then two capacitors,

each of twice the required capacitance and of equal

tolerance and rated voltage, should be connected in a

back-to-back configuration, i.e., both anodes or both

cathodes joined together. This is necessary in order to avoid

a reduction in life expectancy.

This is the maximum RMS alternating voltage, superimposed

on a DC voltage, that may be applied to a capacitor. The

sum of the DC voltage and the surge value of the

superimposed AC voltage must not exceed the category

1.2.8 Voltage derating

Refer to section 3.2 (pages 155-157) for the effect of voltage

derating on reliability.

85°C

125°C

Rated

Surge

Category

Surge

Voltage

Voltage

Voltage

Voltage

(V DC)

(V DC)

(V DC)

(V DC)

2

2.6

1.3

1.7

342

2.6

4

5.2

2.6

3.4

6.3

845

10

13

6.3

9

16

20

10

12

20

26

13

16

25

33

16

21

35

46

23

28

50

65

33

40

1.3 DISSIPATION FACTOR AND TANGENT OF LOSS ANGLE (TAN D)

1.3.1 Dissipation factor (DF)

Dissipation factor is the measurement of the tangent of the

loss angle (Tan ) expressed as a percentage.

The measurement of DF is carried out at +25°C and 120 Hz

with 2.2V DC bias max. with an AC voltage free of harmonics.

The value of DF is temperature and frequency dependent.

1.3.2 Tangent of loss angle (Tan )

This is a measure of the energy loss in the capacitor. It is

expressed as Tan

and is the power loss of the capacitor

divided by its reactive power at a sinusoidal voltage of specified

frequency. (Terms also used are power factor, loss factor and

dielectric loss, Cos (90 - ) is the true power factor.) The meas-

urement of Tan

is carried out at +20°C and 120 Hz with 2.2V

DC bias max. with an AC voltage free of harmonics.

1.3.3 Frequency dependence of dissipation factor

Dissipation Factor increases with frequency as shown in the

typical curves below.

10

F 10V

1.0

F 35V

100

50

20

10

5

2

1

100Hz

1kHz

10kHz

100kHz

Frequency

Typical Curve-Dissipation Factor vs. Frequency

TAP/TEP Technical Summary and

Application Guidelines