Eighteen pulse rectification scheme for use with variable frequency drives
An AC/DC converter system comprises an input circuit for connection to a three phase AC source. An isolation transformer comprises 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 are phase shifted by select amounts from the set of primary windings. The set of primary windings is connected to the input circuit. An AC/DC converter comprises first, second and third three phase rectifiers, the first three phase rectifier being powered by the first set of secondary windings, the second three phase rectifier being powered by the second set of secondary windings, and the third three phase rectifier being powered by the input circuit. An impedance matching inductor is electrically connected between the input circuit and the third three phase rectifier. An output circuit is connected between the AC/DC converter and a DC load.
1 . An AC/DC converter system comprising:
an input circuit 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 phase shifted by select amounts from the set of primary windings, the set of primary windings connected to the input circuit;
an AC/DC converter comprising first, second and third three phase rectifiers, the first three phase rectifier being powered by the first set of secondary windings, the second three phase rectifier being powered by the second set of secondary windings, and the third three phase rectifier being powered by the input circuit; and
an output circuit for connection between the AC/DC converter and a DC load.
2 . The AC/DC converter system of claim 1 wherein the first and second sets of secondary windings are phase shifted by equal and opposite amounts from the set of primary windings.
3 . The AC/DC converter system of claim 1 wherein the first and second sets of secondary windings are phase shifted by +20 electrical degrees and −20 electrical degrees, respectively, from the set of primary windings.
4 . The AC/DC converter system of claim 1 wherein each of the three phase rectifiers comprises a six pulse rectifier.
5 . The AC/DC converter system of claim 1 wherein the input circuit comprises a three phase inductor.
6 . The AC/DC converter system of claim 5 further comprising an impedance matching three phase inductor electrically connected between the input circuit and the third three phase rectifier.
7 . The AC/DC converter system of claim 1 wherein the output circuit comprises parallel connected DC outputs from the bridge rectifiers connected through an output inductor to the DC load.
8 . The AC/DC converter system of claim 1 wherein the set of primary windings comprises three main primary windings and each set of secondary windings comprises three main secondary windings, each in phase with corresponding ones of the three main primary windings, electrically connected to three teaser secondary windings, each in phase with adjacent ones of the three main primary windings, resulting in a vector phase shifted from the phase of the corresponding one of the three main primary windings.
9 . An eighteen pulse converter system comprising:
an input circuit 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 phase shifted by select amounts from the set of primary windings, the set of primary windings connected to the input circuit;
an eighteen pulse rectifier comprising first, second and third six pulse rectifiers, the first six pulse rectifier being powered by the first set of secondary windings, the second six pulse rectifier being powered by the second set of secondary windings, and the third six pulse rectifier being powered by the input circuit; and
an output circuit for connection between the AC/DC converter and a DC load.
10 . The eighteen pulse converter system of claim 9 wherein the first and second sets of secondary windings are phase shifted by equal and opposite amounts from the set of primary windings.
11 . The eighteen pulse converter system of claim 9 wherein the first and second sets of secondary windings are phase shifted by +20 electrical degrees and −20 electrical degrees, respectively, from the set of primary windings.
12 . The eighteen pulse converter system of claim 9 wherein the input circuit comprises a three phase inductor.
13 . The eighteen pulse converter system of claim 12 further comprising an impedance matching three phase inductor electrically connected between the input circuit and the third three phase rectifier.
14 . The eighteen pulse converter system of claim 9 wherein the output circuit comprises parallel connected DC outputs from the bridge rectifiers connected through an output inductor to the DC load.
15 . The eighteen pulse converter system of claim 9 wherein the set of primary windings comprises three main primary windings and each set of secondary windings comprises three main secondary windings, each in phase with corresponding ones of the three main primary windings, electrically connected to three teaser secondary windings, each in phase with adjacent ones of the three main primary windings, resulting in a vector phase shifted from the phase of the corresponding one of the three main primary windings.
16 . 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 phase shifted by select amounts from the set of primary 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;
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 impedance matching inductor electrically connected between the input circuit and the third three phase rectifier; and
an output circuit for connection between the AC/DC converter and a DC load.
17 . The AC/DC converter system of claim 16 wherein the first and second sets of secondary windings are phase shifted by +20 electrical degrees and −20 electrical degrees, respectively, from the set of primary windings.
18 . The AC/DC converter system of claim 16 wherein each of the three phase rectifiers comprises a six pulse rectifier.
19 . The AC/DC converter system of claim 1 wherein the output circuit comprises parallel connected DC outputs from the bridge rectifiers connected through an output inductor to the DC load.
20 . The AC/DC converter system of claim 16 wherein the set of primary windings comprises three main primary windings and each set of secondary windings comprises three main secondary windings, each in phase with corresponding ones of the three main primary windings, electrically connected to three teaser secondary windings, each in phase with adjacent ones of the three main primary windings, resulting in a vector phase shifted from the phase of the corresponding one of the three main primary windings.