Eighteen Pulse Rectification Scheme For Use With Variable Frequency Drives

An AC/DC converter system comprising:

• an input circuit comprising a three phase inductor for connection to a three phase AC source;
• an isolation transformer comprising a set of primary windings and first and second sets of secondary windings magnetically coupled to the set of primary windings, the first and second sets of secondary windings level translated to a higher voltage by an amount in the range of about 2.5% and 5% a from the set of primary windings using independent taps in the secondary windings, the set of primary windings connected to the input circuit;
• an AC/DC converter comprising first, second and third three phase rectifiers each for converting AC power to DC power, each of the rectifiers comprising a six-pulse rectifier;
• the first three phase rectifier being electrically connected to the first set of secondary windings;
• the second three phase rectifier being electrically connected to the second set of secondary windings;
• an inductor electrically connected between the input circuit and the third three phase rectifier, comprising a current balancing three phase inductor matched to the windings of the isolation transformer to balance current flowing into the first, second and third three phase rectifiers;
• and
• an output circuit for connection between the AC/DC converter and a DC load.

An AC/DC converter system comprising:

• an input circuit comprising a three phase inductor for connection to a three phase AC source;
• an isolation transformer comprising a set of primary windings and first and second sets of secondary windings magnetically coupled to the set of primary windings, the first and second sets of secondary windings level translated to a higher voltage by an amount in a range of between about 2.5% and 5% from the set of primary windings by providing taps located in a range of between about −2.5% and −5% in the primary winding, the set of primary windings connected to the input circuit;
• an AC/DC converter comprising first, second and third three phase rectifiers each for converting AC power to DC power, each of the rectifiers comprising a six-pulse rectifier;
• the first three phase rectifier being electrically connected to the first set of secondary windings;
• the second three phase rectifier being electrically connected to the second set of secondary windings;
• an inductor electrically connected between a primary winding tab in a range between about +2.5% or +5% and the third three phase rectifier, comprising a current balancing three phase inductor matched to the windings of the isolation transformer to balance amplitude of current flowing into the first, second and third three phase rectifiers;
• and
• an output circuit for connection between the AC/DC converter and a DC load.