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Page 206

| Figure 11-7 Liquid fuse with separate expulsion chamber. |

| Liquid-Filled Fuses |

| Larger-capacity, high-voltage fuses of the enclosed type may be filled with liquid (Fig. 11-7). One form of such a fuse employs a glass tube cemented into heavy metal end caps and filled with a fire extinguishing fluid such as carbon tetrachloride (Pyrene). The fuse element is held in tension by means of a spring that helps to break the circuit by quickly lengthening the gap and forcing the quenching liquid into the arc. The cap on this end of the tube is usually made to blow off if the pressure becomes excessive, but the gas produced is inert. |

| Sand and Boric Acid Fuses |

| In another type of large-capacity, high-voltage fuse, the fuse element is surrounded by sand. The sand tends to absorb the heat and gases generated when the fuse blows and also to squelch the arc. In still another type, powdered boric acid rather than sand surrounds the fusible element (Fig. 11-8). Exposed to the heat produced when the fuse melts, the boric acid decomposes and forms steam. The steam, being under pressure, acts to snuff out the resultant arc. |

| Oil Fuses.. |

| If severe conditions require an unusually reliable fuse with large interrupting capacity, the oil fuse and associated cut-out is used (Fig. 11-9). Its special features are that it is able to break full load current without expelling arcs or hot gases. The tank is made of steel. Stationary contacts inside the tank are brought out through pothead-type fittings. Moving contacts are of the clip or jaw type, to which the fuse link is connected. Here, the fuse link is fitted and fastened about an insulated assembly that fits into the tank. |

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