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Simple circuit breakers.

of the magnet would die out. This type of circuit breaker would answer every purpose for currents of very low voltage and amperage, but would not operate success

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Two simple forms of circuit breakers.

fully with such currents as are used commercially for lighting and power purposes. It would fail, first, because

Breaker for light power.

the contact between S and N is not perfect enough to prevent overheating, and secondly, because the width of the separation would not be sufficient to prevent the current from continuing to flow across the gap, thus forming an arc that would burn out the contacts in short order. By elaborating the design of Fig. 131, as shown in Fig. 132, we can obtain a device that will operate successfully on a light power circuit.

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Fig. 133 shows one way of reducing the friction, which consists in using a brace jointed at the center, to hold the switch lever in place, this brace being forced out of line by the movement of the lever.

Fig. 134 shows another arrangement by means of which the friction may be reduced. In this construction a solenoid magnet is used, and the main switch is held in position by means of the catch at the end of the small lever I. The lower portion of plunger i is made of iron, and the upper part, which is drawn with lighter shading, is made of brass, and on that account is not attracted by

Solenoid circuit breaker.

the magnetic force of the solenoid. When the solenoid becomes sufficiently strong to raise the plunger i, the pull

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increases as the rod moves up, thus rapidly accelerating the motion, the result being that the end of H strikes K

Carbon break circuit breakers.

an actual blow, the jar of which is great enough to dislodge the catch at the upper end and thus release switch L. By varying the position of i, the force exerted upon it by the solenoid can be changed so that the device can be set so as to trip with currents of different strengths. This position of i is varied by means of the screw A.

The principles illustrated in Figs. 133 and 134 are those most commonly used in the construction of commercial circuit breakers for continuous current circuits. Fig. 135 is a line drawing of a circuit breaker acting upon these principles. The solenoid coil is at B and C is the plunger, while M is the adjusting screw, by means of which the device is adjusted to trip with any desired current. When C is lifted it strikes E and thus throws up the trigger H, allowing the catch F to release G. The plunger I, which is forced outward by the spiral spring, impinges against the switch at K and throws it open, thus breaking the circuit. The switch contacts are arranged with double breakers, one being made of copper and the other of carbon. The copper contacts separate first, and the circuit is finally broken between the carbon contacts.

The carbon break circuit breaker, as manufactured by the General Electric Company, Fig. 137, meets all demands for a small, reliable, automatic, protective device for direct and alternating current systems.

The operation of the circuit breaker is absolutely positive, and it can be adjusted to trip at any predetermined point between its wide limits of calibration. A fuse is inflexible in this respect; its time lag is appreciable and more or less dependent upon climatic conditions; it can never be absolutely relied upon to rupture at its rated capacity.

Through the use of a double or triple pole circuit

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