Longitudinal voltage regulation at the line terminals of a phase shifting transformer

A phase shifting transformer for poly-phase alternating current (AC) with source side terminals and with load side terminals, the phase shifting transformer comprising:

• an exciting unit comprising a first transformer with primary coils connected between pairs of the source side terminals and with secondary coils to provide quadrature voltages;
• and
• a series unit comprising a second transformer with primary coils connected in series between the source side terminals and the load side terminals and with secondary coils to receive the quadrature voltages, thus providing a voltage phase displacement between the source side terminals and the load side terminals;
• wherein the exciting unit comprises further coils that are magnetically coupled to the primary coils and to the secondary coils of the exciting unit to provide further voltages, with the further coils connected in series between the source side terminals and the series unit, so that the voltages at the load terminals are combinations of the quadrature voltages and the further voltages with the source voltages, thus modifying the voltage phase displacement between the source side terminals and the load side terminals.