Book Description

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 edition. Excerpt: ... amperes, 3 dynamo fuse is used. When a dynamo fuse greater than 500 amperes is required, 'wo fuses of equal capacity are mounted in parallel.--ise wire or wire from which fuses are made is furnished 0: wound like cotton, for convenience in cutting off an?: length. It is generally in spools of 3-10-20-40-60 aniperes, above which completed fuses are used. CIRCUIT BREAKER The function of this piece of apparatus is well denned by its name, being a contrivance to break a circuit in case the current rises above a certain fixed value, acting for the same purpose as an ordinary safety fuse; to interrupt a circuit before the current becomes so great as to become dangerous on account of the heat produced. They are placed directly in the circuit to be protected and consist of a double pole switch which when closed is held in place by a trigger against the tension of a very strong quick acting spring. In the circuit on the breaker is an electro-magnet surrounding an iron core which as the magnet is energized by the current is pulled into the hollow of the coil, the amount of the pull depending on the current. As the core is attracted, it is arranged to trip a release trigger, which releases the catch holding the spring, and the latter throws out the switch arms, breaking the circuit. The current for which the release may be effected may be varied by moving by hand the position of the plunger before current is turned on. A small index shows for what current the breaker is set, that is, for what current the switch arms will be released. Circuit breakers are placed in circuits that are liable to a sudden fluctuation in current, and in currents too great to be protected by ordinary safety fuses. If fuses were placed in searchlight circuits, they would...