Inrush currents associated with motor starting and transformer energizing can cause interaction problems with other loads in a facility or on the power system. These inrush currents can cause sags ...

In power distribution systems, three-phase transformer configuration directly impacts system reliability and load management.

So you have an old tube-type transmitter as a backup. It ran perfectly when you last turned it on two years ago to substitute for your then-ailing solid-state main transmitter. Now you need it again.