General Technical Information
www.vishay.com
Vishay Roederstein
Film Capacitors
RFI suppression capacitors are the most effective way to
reduce RF energy interference. As its impedance decrease
with frequency, it acts as a short-circuit for high-frequencies
between the mains terminals and/or between the mains
terminals and the ground.
FILM CAPACITORS
Plastic film capacitors are generally subdivided into film/foil
capacitors and metalized film capacitors.
FILM / FOIL CAPACITORS
Capacitors for applications between the mains terminals are
called X Class capacitors. Capacitors for applications
between the terminals and the ground are called Y Class
capacitors.
Film / foil capacitors basically consist of two metal foil
electrodes that are separated by an insulating plastic film
also called dielectric. The terminals are connected to the
end-faces of the electrodes by means of welding or
soldering.
X-Capacitors
For the suppression of symmetrical interference voltage.
Capacitors with unlimited capacitance for use where their
failure will not lead to the danger of electrical shock on
human beings and animals. The capacitor must present a
safe end of life behavior.
Main features:
High insulation resistance, excellent current carrying and
pulse handling capability and a good capacitance stability.
METALIZED FILM CAPACITORS
Y-Capacitors
The electrodes of metalized film capacitors consist of an
extremely thin metal layer (0.02 μm to 0.1 μm) that is vacuum
deposited either onto the dielectric film or onto a carrier film.
The opposing and extended metalized film layers of the
wound capacitor element are connected to one another by
flame spraying different metals to the end-faces. The metal
spraying process is also known as schooping. The terminals
are connected to the end-faces by means of welding or
soldering. For the production of metalized film capacitors
Vishay film capacitors uses the conventionally wound film.
Capacitors for suppression of asymmetrical interference
voltage, and are located between a live wire and a metal
case which may be touched. High electrical and mechanical
reliability to prevent short-circuits in the capacitors. The
capacitance value is limited, in order to reduce the AC
current flowing through the capacitor. By following these
technical requirements, it is intended that its failure will not
lead to the risk of electrical shock, making the device with Y
capacitor (in conjunction with other protective measures)
safe to human beings and animals.
Main features:
For
detailed
information,
we
refer
to
High volume efficiency, self-healing properties
www.vishay.com/doc?28153.
SPECIAL DESIGN CAPACITORS
SELF-HEALING
For high current applications Vishay film capacitors is also
able to offer special designs such as capacitors with a heavy
edge metalization or a double sided metalization as well as
combinations that have a film/foil and a metalized film
design in one unit. For high voltage applications it is
furthermore possible to offer designs with dual and multiple
sections. Depending on the design these capacitors provide
low losses, high current and pulse carrying capabilities, high
voltages, small dimensions and good self-healing
properties.
Self-healing, also known as clearing, is the removal of a
defect caused by pinholes, film flaws or external voltage
transients. The heat generated by the arcing during a
breakdown, evaporates the extremely thin metalization of
the film around the point of failure, thereby removing and
isolating the short circuit conditions. On Segmented Film
Technology Capacitors, the self healing effect is more
controlled. The film metalization is made by forming a
pattern of segments, which are connected to each other by
micro fuses. This limits the healing current and limits the
self-healing effect to a well defined section of the film.
RFI SUPPRESSION CAPACITORS
There are two main sources of Radio Frequency
Interference (RFI). Devices that due to their construction
produce RF energy, such as oscillators, radio and TV
receivers; and devices that produce a wide spectrum of
frequency, due to rapid variations in electrical current
intensity, such as switch mode power supplies.
The self-healing process requires only μW of power and a
defect is normally isolated in less than 10 μs. Extensive and
continuous self-healing (e.g. at misapplications) will
gradually decrease the capacitance value.
Interference from source to receiver is spread in three ways:
• Along wiring
• By coupling
• By radiation
Revision: 17-May-17
Document Number: 26033
1
For technical questions, contact: dc-film@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
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