This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ...any other type ever used. They will discharge Fig. 69. Aluminum Lightning Arrester for Three-Phaac Circuit Courtesy of Oencral Electric Company for long periods, either continuously or intermittently, without damage. They will take care of surges in voltage as well as lightning. The film on the plates will gradually dissolve if the arresters are left long disconnected from the circuit, and arrangements are always provided for connecting them to the line at intervals to re-form the film. The cells are connected in series with horn gaps, which are adjusted for the particular voltage on which they are to be used. Hvm Type. Lightning arresters installed on are circuits either alternating-current or direct-current, are usually of the horn type. They consist merely of a pair of horn gaps and a series resistance connected to each line. Another form sometimes used consists of a pair of lignum-vitae blocks which have eharned grooves on their faces. These two faces are placed against each other and electrodes are put at each end. The charred grooves serve as a path to ground for the discharges. Accessories. Choke Coils. Choke coils are nearly always installed with lightning arresters. They consist of coils of wire which offer considerable impedance to high frequency discharges but not to the normal operating frequency. They are inserted in the line between the arrester and the apparatus to be protected and help to make the discharge pass into the arrester rather than into the apparatus. Horn Gaps. Horn gaps consist of two pieces of copper wire bent into the shape of goat horns and mounted on insulators. When used on alumiiium cell arresters they are arranged so that one can be swung around and thus act as a disconnecting switch. They are also arranged to be moved in ...
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