The primary winding of the dry-type transformer has taps connected to the tap changers. A Delta-Y switch can also be applied between the three phases on the primary side to adjust the secondary voltage. The -Y conversion is an economical voltage regulation method that can reduce the secondary voltage to half of the original voltage without affecting the primary turns. With 9 taps and a -Y switch per phase, a total of 29 or 18 voltage levels can be obtained.