ALC10C331ED450 BHC COMPONENTS, ALC10C331ED450 Datasheet - Page 8

• Manufacturer Part Number: ALC10C331ED450
• Description: CAPACITOR, 330UF 450V CAPACITOR, 330UF 450V
• Manufacturer: BHC COMPONENTS
• Series: ALC10r

Specifications of ALC10C331ED450

• Capacitance: 330UF
• Voltage Rating, Dc: 450V
• Capacitor Dielectric Type: ALUMINIUM ELECTROLYTIC
• Temp, Op. Max: 85(DEGREE C)
• Temp, Op. Min: -40(DEGREE C)
• Tolerance,: 20%
• Rohs Compliant: YES

6
Basic Construction of a Capacitor
The basic principle of the capacitor is to store electrical
charge (Q in coulombs). The potential charge it can hold is
determined by the capacitance (C in Farads) and voltage (V
in volts) and is defined as:-
The unit of capacitance, the Farad, is the capacitance
of the capacitor between the plates across which there
appears a potential difference of 1 volt when it is charged
by 1 coulomb of electricity. The value of capacitance in a
basic capacitor is proportional to the area of the plates and
inversely proportional to the distance between them. Not
only does this distance between the plates have an effect on
capacitance but also the material that occupies the space,
known as the dielectric.
If the space were to be occupied by a perfect vacuum then
the capacitance can be determined by:
A =
d =
∈
In practice this space is occupied by a dielectric which has a
relative permittivity to that of the vacuum as follows:
Therefore capacitance is determined by:
∈
0
r
Air
MATERIAL
Vacuum
Paper (dry)
Polythene
Insulating oil
Bakelite
Glass
= relative permittivity of the dielectric
= permittivity of free space - 8.85 x 10
dielectric
surface area of the plates in m
distance between the plates
(or dielectric thickness) in m
+ve
C = ∈
d
C = ∈
Q = C . V
0
. ∈
0
. A
r
d
RELATIVE PERMITTIVITY
1.0
1.0006
2 - 2.5
2 - 2.5
3 - 4
4.5 - 5.5
5 - 10
. A
2
d
A = surface area
-ve
-12
F/m
Aluminium Electrolytic Capacitors
The aluminium electrolytic capacitor consists basically of
two foils interleaved with an absorbent paper wound tightly
into a cylinder. The main advantage of this type of capacitor
is the high capacitance per unit volume due to its internal
construction which consists of a very thin dielectric layer
and large effective surface area.
The positive plate, or anode, is made from aluminium foil
which is etched to increase the surface area. The dielectric
is aluminium oxide, which is formed electrolytically onto
the surface of the foil. This formed oxide layer is very
thin, being proportional in thickness to the forming voltage
and possesses a semiconductor characteristic. The oxide
thickness for a 25 volt working capacitor is in the order of
0.045 microns.
The negative plate, or cathode, is provided by an electrolyte
solution for two reasons:
 allows good contact with the anode by
 repairs any flaws in the oxide layer when the
The second foil, usually called the cathode foil, contacts
with the electrolyte reducing the series resistance. This
foil has a thin stabilized oxide film, and therefore will also
possess a very high capacitance. Like the anode foil the
cathode is also etched to increase the surface area. This
is necessary in order to eliminate the effect on the overall
capacitance by the presence of the cathode foil.
equivalent circuit
aluminium foil
permeating all the etched structure.
capacitor is polarised.
C
total
1
dielectric
=
anode
anode
C
anode
1
electrolyte solution
Capacitor Construction
cathode
paper soaked in electrolyte
cathode
+
aluminium foil
C
cathode
1