PRINT VERSION OF INVESTIGATION ON CAPACITORS
Investigation on Capacitors
Electrolytic
Capacitors (or e-caps)
It is named
this way due to the electrolyte it uses. It enables a larger capacitance to be
achieved than other types. There are several disadvantages of using this type,
including its short lifespan. All products in this category should have a
longer leg signifying that it is polarized. The electrolyte may be wet or it
may be a polymer. The capacitors are mainly made of either aluminium or
tantalum. The cheap and common aluminium types must be connected the right way,
otherwise, due to the aluminium oxide/dielectric getting damaged, a short
circuit will occur between the two terminals. The large current running through
it will create heat that can vaporize or melt the electrolyte leading to a
burst of the covering. There is a non-polarized type available for AC use.
Aluminium capacitors are made with two conducting aluminium foils and a spacer
soaked in electrolyte. One of the aluminium foils is covered with an oxide
layer, and that foil acts as the anode, while the uncoated one acts as a
cathode.
Polyester
Capacitors
These
usually will be made with PET plastic (for the dielectric) and are a type of
film capacitor. They come in many types, and do not absorb much moisture, so
they can be used easily in most projects. They are cheap, small but come with
high capacitance. Thelengths of the legs are the same, as it is non-polarized. The
plastic may look the same but can be different types. The glossy types are
usually manufactured through dipping. SMD and Radial are the two common styles.
MKT Capacitors
Somewhat
expensive, MKT capacitors are characterized by its equal length between leads.
M stands for metallized construction, K stands for plastic film capacitor, and
T signifies the material of the dielectric, which in this case, is Polyester /
PET. Therefore, it would seem to be very similar to the polyester green caps.
They are good for designing. There are 3 different sets of length between the
leads as shown in the picture. There may be more.
Tantalum Electrolytic Capacitors
They
are similar to electrolytic capacitors as they are polarized. The negative
leads are shown with the symbols on the case/covering. These are used in small
or portable consumer devices or military technology. The anode is made of
tantalum and it is the oxide layer that is formed which is the dielectric. The
electrolyte (polymer or manganese dioxide) covering the oxide layer is the
cathode. Its low weight and high capacitance make it much valued. It is the
cost of tantalum which causes the high price. It must be connected the right
way, otherwise it may be destroyed. Its stability and small size have led to it
being favoured by the military and medical facilities. It can also be used in
consumer electronic products as filters of electricity.
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