In order to get an output of 240 V with an input of only
444 V, the turns ratio will have to be changed to 1. 85 to
1. The purpose of the tap connections, usually on the
primary, is to change easily the transformer turns ratio.
A typical single-phase transformer nameplate with primary
taps is shown in Figure 14-19.
Winding taps each make a 21/2% change in the voltage.
A transformer will often have two taps above normal
voltage and four taps below normal voltage. A transformer
usually comes reconnected for normal voltage.
If an abnormal voltage is present, it is up to the installer
to change the tap connections.