Dielectric Strength Overview
an insulating material, the maximum electric field
that a pure material can withstand under ideal
conditions without breaking down (i.e., without
experiencing failure of its insulating properties).
For a specific configuration of dielectric material
and electrodes, the minimum applied electric field
(i.e., the applied voltage divided by electrode
separation distance) that results in breakdown.
theoretical dielectric strength of a material
is an intrinsic property of the bulk material
and is dependent on the configuration of the material
or the electrodes with which the field is applied.
The "intrinsic dielectric strength"
is measured using pure materials under ideal laboratory
conditions. At breakdown, the electric field frees
bound electrons. If the applied electric field
is sufficiently high, free electrons from background
radiation may become accelerated to velocities
that can liberate additional electrons during
collisions with neutral atoms or molecules in
a process called avalanche breakdown. Breakdown
occurs quite abruptly (typically in nanoseconds),
resulting in the formation of an electrically
conductive path and a disruptive discharge through
the material. For solid materials, a breakdown
event severely degrades, or even destroys, its
Strength Of Connectors
strength is a measurement that is related with
the insulating material in a connector. An insulating
material behaves like an insulator only up to
a certain higher voltage ranges, after that dielectric
breakdown occurs and the material suddenly starts
conducting electricity like a conductor. Dielectric
strength is the maximum voltage up to which the
insulating material can keep its insulating property
without causing dielectric breakdown. It is otherwise
called Dielectric withstanding voltage, Breakdown
voltage, Withstanding voltage, Voltage proof etc.
Operating the connector above this range may cause
dielectric breakdown. Hence this parameter is
very important in high voltage applications. The
Dielectric Strength Voltage of an unshielded RJ
male plug is typically 1000V AC (RMS 60Hz).
Affecting Dielectric Strength With Connectors
Increases slightly with increased thickness.
2. Decreases with increased operating temperature.
3. Decreases with increased frequency.
Breakdown Field Strength
field strength at which breakdown occurs depends
on the respective geometries of the dielectric
(insulator) and the electrodes with which the
electric field is applied, as well as the rate
of increase at which the electric field is applied.
Because dielectric materials usually contain minute
defects, the practical dielectric strength will
be a fraction of the intrinsic dielectric strength
of an ideal, defect-free, material. Dielectric
films tend to exhibit greater dielectric strength
than thicker samples of the same material. For
instance, the dielectric strength of silicon dioxide
films of a few hundred nm to a few £gm thick is
approximately 0.5GV/m. However very thin layers
(below, say, 100 nm) become partially conductive
because of electron tunneling. Multiple layers
of thin dielectric films are used where maximum
practical dielectric strength is required, such
as high voltage capacitors, and pulse transformers.