Fig. 2,269.—Diagram of General Electric shunt trip with coil connected beyond breaker and thrown out of circuit after tripping.
Ques. Describe the auxiliary circuit trip.
Ans. A pressure coil is used which is energized by current from an auxiliary circuit. The coil is only momentarily energized, by push button, relay or other control, as distinguished from the preceding types, in which the coil is constantly energized.
Fig. 2,270.—Diagram of General Electric shunt trip with auxiliary circuit opening switch to throw coil out of circuit after tripping.
Fig. 2,271.—General Electric shunt trip attachment. The shunt trip attachment has been designed to provide for conditions under which the low voltage attachment cannot be successfully applied. It resembles the low voltage attachment in construction, but differs in that it trips the circuit breaker when energized. The shunt trip should be allowed to remain only momentarily in circuit; hence it should be so connected that the opening of the circuit breaker immediately disconnects it from the circuit. Whenever it is impossible to connect the shunt trip in this manner, the circuit opening auxiliary switch should be used in connection with it.
Fig. 2,272.—General Electric low voltage attachment for circuit breakers. This low voltage trip is designed to operate the circuit breaker when the line voltage drops to approximately 50 per cent or less of the normal voltage. It should be noted that the coil is always in circuit, as is the case with the overload and underload coils, and that it operates with the releasing of its armature. It is always necessary to use a fixed amount of resistance (depending upon the voltage of the system) in series with the low voltage release. The low voltage release performs the functions of a shunt trip coil when used in conjunction with a push button, auxiliary switch or speed limiting device, and is generally preferred to the shunt trip attachment.