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Product Safety
In
certain instances capacitor failures may result in
case rupture due to gases generated internally. Since
the elimination of the PCB impregnants for environmental
reasons all the impregnants now in use are classified
as combustible and carry a NFPA(National Fire Protection
Association)designation of type III B. Liquids with
this classification, such as mineral oil and bland
oil have been in use for over 40 years with excellent
safety records. Even if rupture does occur, the probability
of fire is still low as the right conditions of temperature
and source of ignition(i.e.an electrical arc) must
be present. In order to reduced the possibility of
capacitor rupture the NUINTEK CO.,LTD. Now incorporates
an internal protection mechanism into DNK,RNV anal
SNV series capacitors where the construction and application
conditions allow. The listings of each family of capacitors
indicate if internal protection is included or not.
The protective mechanism is the Pressure Sensitive
Interrupter.
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Pressure Sensitive Interrupter
The
Pressure Sensitive Interrupter or PSI was developer
by the NUINTEK CO.,LTD. It senses the build-up of
pressure with in the capacitor and interrupts the
internal connections taking the capacitor out of the
circuit before rupture can occur, as shown in Figure.
The fault current is the maximum current that the
circuit can provide if the capacitor becomes a short
circuit. IT IS THE RESPONSIBILITY OF THE CAPACITOR
USER TO DETERMINE WHAT THE AVAILABLE FAULT CURRENT
IS.

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