generator load and cranks the diesel engine with a
engine shuts down after a cooling-off running period.
minimum drop in frequency during the transition.
The electric motor and flywheel continue to operate.
Figure 2-12 shows the unit in standby operation and
After the diesel engine comes up to speed, it assumes
figure 2-13 shows the unit online.
the load and continues to produce power to meet the
b. Another method for providing uninterruptible
load requirements. During diesel operation, the com-
power which is being utilized in overseas AUTODIN at
mercial power is constantly monitored for voltage and
the Automatic Digital Message Switching Centers
frequency. When the commercial power returns to the
(ADMSC's) is shown in figure 2-13. This type of a UPS
correct voltage and frequency, normal operation is
may also be found at DCS Stations other than those
resumed, that is the commercial line contractor closes,
the magnetic clutch is deenergized, and the diesel
collocated with an ADMSC.
Figure 2-11. Uninterruptible power supply in standby condition.
Figure 2-12. Uninterruptible power supply in on-line condition.