Introduction
www.vishay.com Vishay Roederstein
Revision: 30-Jan-14 6Document Number: 25001
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ALTERNATING CURRENT
The alternating current is defined as the effective value of
the alternating current with which the capacitor is charged.
Rated Alternating Current IR
The permissible rated alternating current is defined in such
a way that at an upper category temperature TUC and at a
frequency of 100 Hz (measuring frequency of capacitance
and dissipation factor), the temperature of the case surface
area rises by 3 K. The resulting AC values IR are indicated in
the datasheets for each capacitor.
Maximum Permissible Alternating Current I, AC Rating
The maximum permissible alternating current rating
depends on ambient temperature Tamb' case surface area
Fs' equivalent series resistance RESR (or the dissipation
factor tan ), as well as on excess surface temperature T
(temperature rise, difference between surface temperature
Ts and ambient temperature Tamb). The permissible
temperature rise T is specified by the respective
manufacturer. For Vishay Roederstein electrolytic
capacitors this value is based on IEC 60384-4 and is 3 K in
relation to the upper category temperature TUC. Due to the
temperature and frequency dependence of the equivalent
series resistance RESR (or the dissipation factor tan ) the
maximum permissible alternating current is also dependent
on the alternating current frequency f. Since the life
expectancy of an electrolytic capacitor is considerably
determined by its thermal load (permutation model, see
section Lifetime), the temperature rise caused by an AC load
presents a significant factor of the capacitor's lifetime. The
individual lifetime tables show the interrelation between the
maximum permissible alternating current I, the ambient
temperature Tamb' the surface temperature Ts' the
alternating current frequency f, as well as the lifetime.
(Sections Standard Lifetime Conversion Table and Type
Specific Lifetime Conversion Table explain the use of these
tables.)
ELECTRICAL STRENGTH OF THE INSULATION
The insulating sleeve can withstand a voltage of at least
1000 V.
INSULATION RESISTANCE OF THE INSULATION
The insulation resistance of the sleeve material is a minimum
of 100 M.
CLIMATIC CONDITIONS
For reasons of reliability and due to the temperature
dependence of electrical parameters certain limits have to
be observed for the climatic conditions. The upper and
lower category temperature are considered important
climatic conditions for electrolytic capacitors. Furthermore
the degree of humidity has to be taken into account. These
three values are indicated in coded form in the applicability
class and lEG climatic category (see section Climatic and
Applicability Categories).
Upper Category Temperature TUC
The use of electrolytic capacitors is subject to specific upper
temperature limits. Exceeding these limits may result in early
failure of the capacitor. To avoid this, upper category
temperatures are fixed which indicate the maximum
permissible ambient temperature of the capacitor for
continuous operation. The upper category temperature is
given with the temperature range value in the datasheets.
Sections Maximum Permissible Alternating Current I, AC
Rating and Lifetime have shown that the electrolytic
capacitor's lifetime and reliability depend considerably on
the capacitor's temperature. This is why Vishay recommend
using the capacitor at the lowest temperature possible to
increase lifetime and reliability. Furthermore, Vishay
recommend mounting the electrolytic capacitors inside the
units at positions having a low ambient temperature.
Lower Category Temperature TLC
Due to an impaired electrolytic conductivity, a decreasing
temperature results in higher values for impedance and
dissipation factor (or RESR values). Most capacitor
applications limit such an increase to specific threshold
values. For this reason it is practical to stipulate a lower
category temperature which is also indicated in the
temperature range value given in the datasheet. It should be
emphasized, however, that an operation below the specified
lower category temperature is possible without damaging
the capacitor. This is particularly true if the capacitor is
exposed to an alternating-current load. Compared to the
lower ambient temperature, the alternating current flowing
through the increased equivalent series resistance can heat
the electrolytic capacitor to such an extent, that its
properties still ensure proper functioning of the unit.
Climatic and Applicability Categories
According to DIN 40040 the applicability class is given in
form of a three-letter code. The IEC publication indicates a
so-called Category (IEC Climatic Category). The datasheets
list both specifications. The first letter in the DIN 40040
formula stands for the lower category temperature, the
second for the upper category temperature, and the third for
the permissible humidity.
Note
(1) Rare and mild formation of dew permissible
DIN CLIMATIC CATEGORY
1st letter
lower category
temperature
F
-55 °C
G
-40 °C
H
-25 °C
2nd letter
upper category
temperature
K
125 °C
M
100 °C
(105 °C)
P
85 °C
S
70 °C
3rd letter
relative humidity/
annual average
30 days/year max.
occasional formation
of dew permissible
C
95 %
100 %
100 %
yes
D
80 %
100 %
90 %
yes
E
75 %
95 %
85 %
yes (1)
F
75 %
95 %
85 %
yes
56 days damp heat (tested according to IEC 60068-1)
40/085/56
Upper category temperature 85 °C
Lower category temperature - 40 °C