Capacitor Expulsion Fuse


Cooper Power Systems offers a wide variety of fuse kV and amp ratings for use on both horizontal and vertical capacitor block bank configurations. The bus-mounted expulsion-type capacitor fuse provides highly reliable, economical protection for capacitor banks where medium energy- interrupting ability is required.

In the event of a capacitor fault, excess current will flow through the fuse of the faulted unit. This current causes the fuse element to melt and vaporize. An arc will form across the vaporized section within the fuse tube. The function of the fuse tube and ejector (or flipper) spring is to extinguish the arc and eliminate the possibility of its re-establishment.

Flipper Spring Information

Catalog Number FN5B1, FN10B5, FN19B1, FN11B1, FN13B3, FN20B1, FN14B1
Fuse Max Voltage 8.7 - 23 kV
Capacitor Voltage Ratings 2.4 - 21.6 kV
Current Rating 50 or 80 A
Interrupting Rating 10,000 - 15,000 J


Fuse Tube Design Features

The fuse tube is constructed of bone-grade fibre overwrapped with epoxy-bonded filament-wound fiberglass or grade XX phenolic. The upper contact, depending on the rating, is either eluminum or tin-plated bronze. The fuseholder accepts ANSI standard removable or non-removable buttonhead fuse links.

The function of the fuse tube is to confine the arc and produce arcquenching gases which are expelled from the end of the tube.

Voltage stress across the fuse tube is eliminated by the gap between the end of the fuse tube and the capacitor terminal. There is no possibility of tracking and eventual flashover, even after exposure to weather and contaminants. When the spring ejects the leader, positive indication of a blown fuse can also be easily detected from a distance.

Ejector Spring Design Features

The ejector spring is constructed of non-current-carrying stainless steel. The spring serves to move the leader end of the fuse out of the tube.

Cooper Power Systems ejector springs are engineered to control lateral motion of the fuse leader during ejection. If lateral motion is not controlled the leader can strike adjacent capacitor units resulting in unnecessary fuse operation and possible capacitor failures.

The geometry of the ejector springs are optimized to ensure that no dragging of the leader across the mouth of the fuse tube or leader cutting will occur. Either of these two effects can impede the proper operation of the fuse.

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