Abstract: A trip unit, such as one comprising a current sensor generating a current signal indicative of current in a power circuit, an analog to digital converter converting said signal into digital form, and a controller monitoring the current signal and sensing whether an over current condition exists and whether a ground fault condition exists. In case of an over-current condition, the controller causes a trip signal to be output resulting in the power circuit being opened. In the case of a ground fault condition, the controller causes an annunciation output signal but does not generate a trip signal in the case of a ground fault condition and therefore does not cause the power circuit to be opened.

Abstract: The smoke detector is powered by standard AC current and a stand-by power source consisting of rechargeable batteries. A detector is provided for detecting the loss or failure of AC power, and the shift to the stand-by power source. The power loss detector initiates a time delay after which the smoke detector signal alarm is energized to alert the user about the loss of AC power. If AC power is restored before the time delay interval, the signal is not energized since the user need not be alerted. If the alarm is energized to alert the user of a loss of AC power, a manual reset switch may be used to terminate the alarm. If the manual reset switch is not used, the alarm is terminated automatically upon the restoration of AC power.

Abstract: Demonstrator apparatus utilizes a display to portray in log-log coordinate scale the trip-time curve of a solid state (static) trip circuit breaker. A simulated static trip unit programmer is selectively adjustable to vary the shape and position of the displayed trip-time curve. An overlay bearing the trip time-current curve for a prospective upstream or downstream circuit protective device is superimposed on the display and the programmer adjusted to demonstrate selective trip coordination. Alternatively, a pair of simulated trip unit programmers are connected to the display to jointly portray thereon a pair of trip-time curves. Also disclosed is the utilization of a computer to generate on a display plural time-current response curves of a series of circuit protective devices selected on the basis of specific distribution system parameters to provide requisite system protection and response coordination.

Abstract: A molded circuit breaker case complete with line and load terminals is fashioned to house a molded case circuit breaker. Rigid conductive straps affixed to the outer case provide electrical connections between the case line and load terminals and the circuit breaker line and load terminals, respectively, and, in addition, serve to secure the circuit breaker in place. The circuit breaker operating handle protrudes through an opening in the outer case to facilitate manual circuit breaker operation.