IBM System/7 Functional Characteristics - All about the IBM 1130 ...

Power WarningSystem/7 circuits are protected from adverse power conditions by sensing circuits thatcheck the input line voltage in each 5026 Enclosure. When the input power falls below85 percent of nominal voltage, the sensing circuits alert the processor module with apower/thermal warning interruption request as shown in Figure 3-6. The time betweenwarning and shutdown depends on the system load and the type of input power failure.This time is a minimum of eight milliseconds with an instantaneous primary power shutdown,for a System/7 containing close to the maximum possible number of I/O modules.Power shutdown to an enclosure occurs when the primary power falls to approximately60 percent of its rated value. If input power remains below 85 percent but does not fallenough to completely shut down the power system, the power warning status indicatorto the processor module remains active.Note: The power warning feature just described is an optional feature in System/7enclosures. However, loss of any one of the several different voltages used in the systemwill remove power from the entire enclosure in order to protect the electronic circuits.100%85%Slope varies dependingon load and nature ofPrimary ac failureTimeWarning ShutdownFigure 3-6. Power failure warningThermal WarningIn order to protect the electronic components within the system, each module in a 5026Enclosure contains a temperature sensing mechanism. Should the operating temperaturein a module approach an excessively high value the sensing mechanism alerts the processormodule with a power/thermal warning interruption request. A status indicator to theprocessor can be checked by the System/7 program to determine if the master unit or aremote unit caused the warning. If the over-temperature condition exists for 1 to 6 seconds,the sensing mechanism shuts off power to that enclosure. The over-temperature condition isalso indicated by the thermal light on the operator console. When the thermal light goes off,power can be restored by turning the power switch to off and then to on.A thermal power shutdown in the master unit shuts off power to all enclosures configuredin the system. However, a power shutdown in a remote unit shuts off power tothe remote unit only.3-14 GA34-0003