Autotransformer rectifier unit
The present improvement essentially integrates a DC link inductance within an interphase power transformer (IPT). The integration is achieved by creating auxiliary magnetic paths for leakage inductance inside the IPT core. The magnetic path can be created, for example, by incorporating extra portions of magnetic material commonly referred to hereinafter as shunts. The IPT flux shared between windings does not cross these shunts. Therefore, this magnetic path increases the self-inductance of the IPT but does not contribute to the mutual inductance between windings. This extra magnetic path allows for leakage inductance of a much higher quantity than that achievable with a conventional IPT.
1. A system for converting AC electric power to DC electric power, the system comprising:
an n×6 pulse autotransformer, where n is an integer of 3 or more;
n rectifier bridges; and
two interphase transformers (IPT 1 , IPT 2 ) comprising n limbs with windings there around, at least a first one of said two interphase transformers being an interphase transformer comprising:
a core defining three or more limbs; and
a winding provided around each limb characterised by means incorporated in or on said core for creating auxiliary magnetic paths for flux generated by at least one of the windings, wherein the means for creating auxiliary magnetic paths comprises limbs of magnetic material formed external to and adjacent to the score.
2. The system of claim 1 , wherein the means for creating auxiliary magnetic paths comprises a shunt of magnetic material provided between adjacent wound limbs.
3. The system of claim 1 , wherein the means for creating auxiliary magnetic paths comprises an additional limb defined by the core between adjacent limbs with windings, the additional limb not having a winding; the additional limb interrupted by an air gap.
4. The system of claim 1 , wherein the means for creating auxiliary magnetic paths comprises an additional number of turns in one or more of the windings.
5. The system of claim 1 , wherein a second one of the at least two interphase transformers is an interphase transformer comprising:
a core defining three or more limbs; and
a winding provided around each limb characterised by means incorporated in or on said core for creating auxiliary magnetic paths for flux generated by at least one of the windings.