Fig. 2,264.—Diagram of General Electric low voltage trip, with tripping switch normally closed.
Ques. What is the object of the overload trip?
Ans. It is intended to open the circuit when the current exceeds a predetermined value.
Ques. What modifications are made in the mechanism shown in the elementary diagrams?
Ans. Sometimes a latch is used in place of the toggle and a magnet in place of the solenoid as in figs. 2,265 and 2,266.
Ques. Why is a magnet used in combination with a latch?
Ans. Because with this arrangement very little movement is required to trip the breaker, and for such conditions, a magnet is more efficient than a solenoid.
Figs. 2,265 and 2,266.—Circuit breaker with automatic control mechanism consisting of magnet and latch; views showing breaker in open and closed positions, and essential features. The toggle is used to obtain sufficient leverage to easily close switch against the pressure of the brush contacts but not to lock switch, this being done by the latch as shown, the latter closing by the action of a spring, there being a roller R at the end which engages the arm to reduce friction. In operation, when the current exceeds a predetermined limit the magnet attracts the latch and releases the contact arm. The brush contacts which are exerting pressure against the contact arm, rapidly push it away, and assisted by gravity, the arm flies open to the position shown in fig. 2,266.