Transformer tap-changing circuit and method of making same

A method of making a transformer tap-changing circuit comprising:

• coupling a secondary winding of a transformer to a first rectifier and to a second rectifier;
• and
• coupling the first and second rectifiers to a DC bus;
• wherein the secondary winding is configured to inductively couple to a primary winding of the transformer when a current from an energy source is passed through the primary winding;
• wherein the first rectifier is configured to rectify a first AC voltage from the secondary winding into a first DC voltage;
• wherein the second rectifier is configured to rectify a second AC voltage lower than the first AC voltage from the secondary winding into a second DC voltage lower than the first DC voltage;
• wherein the DC bus is configured to receive the first and second DC voltages from the first and second rectifiers;
• and
• wherein coupling the first rectifier to the DC bus comprises:
• coupling a controllable switch between the first rectifier and the DC bus;
• and
• configuring a controller to control the controllable switch to selectively couple the first rectifier to the DC bus to cause the first DC voltage to be transferred to the DC bus.

A system comprising:

• a DC bus;
• a variable DC load coupled to the DC bus;
• a transformer comprising a secondary winding configured to inductively couple to a primary winding when a current is passed through the primary winding from an energy source;
• a first rectifier coupled to the secondary winding and configured to rectify a first AC voltage from the secondary winding into a first DC voltage;
• a second rectifier coupled to the secondary winding and configured to rectify a second AC voltage lower than the first AC voltage from the secondary winding into a second DC voltage lower than the first DC voltage;
• a controller configured to cause the first DC voltage to be supplied to the DC bus;
• and
• a pair of controllable switches coupling the first rectifier to the second rectifier;
• wherein the first and second rectifiers comprise a plurality of diodes configured to rectify the first and second AC voltages into the first and second DC voltages, respectively;
• and
• wherein the controller is configured to control the controllable switches to cause the first DC voltage to be supplied to the DC bus.

An apparatus comprising:

• a transformer comprising a secondary winding configured to inductively couple to a primary winding when a current is passed through the primary winding from an energy source;
• a first rectifier coupled to the secondary winding and configured to rectify a first AC voltage from the secondary winding into a first DC voltage, the first rectifier comprising a first plurality of silicon-controlled rectifiers;
• a second rectifier coupled to the secondary winding and configured to rectify a second AC voltage from the secondary winding into a second DC voltage;
• a DC bus coupled to the first and second rectifiers and configured to receive the first and second DC voltages therefrom;
• and
• a controller configured to control the first plurality of silicon-controlled rectifiers to rectify the first AC voltage into the first DC voltage;
• wherein the first AC voltage is higher than the second AC voltage;
• and
• wherein the first DC voltage is higher than the second DC voltage.

An apparatus comprising:

• a transformer comprising a secondary winding configured to inductively couple to a primary winding when a current is passed through the primary winding from an energy source;
• a first rectifier coupled to the secondary winding and configured to rectify a first AC voltage from the secondary winding into a first DC voltage;
• a second rectifier coupled to the secondary winding and configured to rectify a second AC voltage from the secondary winding into a second DC voltage;
• and
• a DC bus coupled to the first and second rectifiers and configured to receive the first and second DC voltages therefrom;
• wherein the first and second rectifiers comprise a plurality of diodes configured to respectively rectify the first and second AC voltages into the first and second DC voltages;
• and
• further comprising:
• a controllable switch coupled to the DC bus and configured to couple the first rectifier to the second rectifier and to the DC bus;
• and
• a controller configured to control the controllable switch to selectively couple the first rectifier to the DC bus to cause the first DC voltage to be transferred to the DC bus;
• wherein the first AC voltage is higher than the second AC voltage;
• and
• wherein the first DC voltage is higher than the second DC voltage.