The FN7-12 Indoor High Voltage Load Switch-Fuse Combination Unit employs gas-generating arc quenching technology, a proven and reliable interruption method distinct from SF₆ or vacuum technologies. This design utilizes specialized arc-extinguishing materials that, when exposed to the high temperature of an electric arc, release a stream of cold gas that rapidly cools, elongates, and extinguishes the arc . For 12kV systems, this mechanism provides consistent interruption performance without requiring complex support systems.
During switch opening, the arc forms between the moving and stationary contacts. The heat instantly decomposes the arc-extinguishing material—typically a fiber-based composite—producing a high-pressure gas flow directed through the arc zone . This process achieves reliable interruption of load currents up to 630A and, when combined with the fuse, enables full short-circuit protection. The quenching action is self-contained, requiring no external gas supply or periodic refilling.
The gas-generating design offers significant practical advantages. Unlike SF₆ switches, there is no risk of greenhouse gas leakage or need for pressure monitoring systems . Compared to air-break switches, the enclosed arc chamber provides consistent performance regardless of ambient humidity or contamination. The technology has been field-proven over decades in thousands of installations worldwide, representing a mature, low-risk solution for standard distribution applications .
The FN7-12's version utilizes this technology in a compact, fixed-type enclosure suitable for indoor mounting. The arc chamber is fully enclosed, protecting operators from arc flash exposure. The rated short-circuit making capacity of 31.5-50kA (depending on current rating) and power frequency withstand voltage of 42kV (phase-to-phase/ground) and 48kV (across open contacts) demonstrate the design's robust dielectric performance .
Therefore, for utilities and industrial users seeking proven, environmentally simple interruption technology for 12kV transformer and feeder protection, the FN7-12's gas-generating design delivers reliable performance without SF₆ handling requirements. Putai also supports customization and the supply of related medium-voltage accessories to meet system integration needs. For a detailed comparison of arc quenching technologies for your application, contact our technical team.
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