Fossil-fired generators require auxiliary power to start pumps, fans and pulverizers to fire up the
boiler, lubricate the bearings, etc. A startup transformer (RAT) connected to the system is therefore
required. This transformer is also available as a spare for the UAT and must be sized accordingly.
There are many possible schemes to connect the RAT to the system and bus. One common scheme
is as shown in Figure 8.19.