Ceramic capacitors. Only a few manufacturers in the world are able
to produce excellent and special types of ceramic capacitors applicable
for moderate high voltage. Most types of these ‘ceramic radio frequency
power capacitors’ are made from ‘class/type 2’ ceramic. The dielectric
material used for this kind of ceramic contains mostly alkaline earth titanates
giving quite high values of permittivity. This material is prone to ageing
caused by a gradual realignment of the crystalline structure, has very high
temperature coefficients (TC), is voltage dependent and is not recommended
for measurement purposes. There are, however, some kinds of ‘class/type 1’
ceramic without these disadvantages. Within this class 1 ceramic, mainly
manufactured from titanium dioxide or magnesium silicate, the materials with
relative permittivities below 1000 show TC values down to some 10 ppm/°K
within a temperature range of 25 to C95°C and very low dissipation factors
up to the Megahertz range. The main advantage of all types of ceramic
capacitors is the extremely low inductance due to their design, which is either
of tubular or plate/pot type with conductive noble metal electrodes. The only
disadvantage is due to the limitations in rated continuous a.c. voltage (up to
about 40 kV peak) and capacitance (up to about 6 nF) per unit.
Ceramic capacitors. Only a few manufacturers in the world are able
to produce excellent and special types of ceramic capacitors applicable
for moderate high voltage. Most types of these ‘ceramic radio frequency
power capacitors’ are made from ‘class/type 2’ ceramic. The dielectric
material used for this kind of ceramic contains mostly alkaline earth titanates
giving quite high values of permittivity. This material is prone to ageing
caused by a gradual realignment of the crystalline structure, has very high
temperature coefficients (TC), is voltage dependent and is not recommended
for measurement purposes. There are, however, some kinds of ‘class/type 1’
ceramic without these disadvantages. Within this class 1 ceramic, mainly
manufactured from titanium dioxide or magnesium silicate, the materials with
relative permittivities below 1000 show TC values down to some 10 ppm/°K
within a temperature range of 25 to C95°C and very low dissipation factors
up to the Megahertz range. The main advantage of all types of ceramic
capacitors is the extremely low inductance due to their design, which is either
of tubular or plate/pot type with conductive noble metal electrodes. The only
disadvantage is due to the limitations in rated continuous a.c. voltage (up to
about 40 kV peak) and capacitance (up to about 6 nF) per unit.
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