Switchboards for Power, Light and Railway Service, Direct and Alternating Current, High and Low Tension (Paperback)

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. 1906 Excerpt: ... inches and will conduct about 700 amperes; therefore, the thickness should be about-Hi inch, which would give a cross section of Yo, inch. The contact surfaces should be as true as they can be made without going to the expense of scraped surfaces, and the bars should be held together with iron bolts or screws, the latter being used for small bars. The number of screws should be not less than two in any case, otherwise the joints may twist around and become loose. It is better to use four small bolts than two large ones, as, with the increased number the pressure is more evenly distributed and the contact of the surfaces is made more complete. Iron bolts are better than brass or copper, not only because they are stronger, but also because they do not expand as much as the copper bars with increase in temperature. Therefore, the warmer the joint becomes the more perfect the contact, as the difference in expansion increases the pressure. The supporting frame of a switchboard is a very simple structure, consisting of vertical angle irons placed at the sides of the board, and intermediate angles located where By amalgamating the contacts on bus bars or switches with the Harold Brown process and using a thin layer of Plastic Alloy, the contact surfaces may be reduced to one square inch per 1000 amperes without danger of heating and a permanent joint of very low resistance obtained. 80 Switchboard construction. the marble slabs join. These angle iron bars run down to the floor and thus form the legs of the structure. If the board is so small that it can be made of a single slab Figure 35. Another method of fastening. there will be only two angle bars, one at each side. At the bottom of the board the vertical angle bars are tied together by means of a horizontal b...