Zero-sequence blocking transformer
A zero-sequence blocking transformer includes a first core part, a first pair of windings wound around the first core part, a second core part and a second pair of windings wound around the second core part, the first core and the second core having a geometry to generate a leakage inductance.
1. A zero-sequence blocking transformer comprising:
a single core defining a closed magnetic path around which at least six windings are wound, the single core having:
a first core part;
a first pair of the four windings wound around the first core part;
a second core part;
a second pair of the four windings wound around the second core part, the first core and the second core;
a third core part;
a third pair of windings wound around the third core part;
wherein the first, second and third core parts combine to form the single core; and
wherein the single core further include leakage core part connected in parallel with the first, second and third core parts and around which no windings are wound.
2. A zero-sequence blocking transformer as claimed in claim 1 , wherein the first core part, the second core part and the third core part are first, second and third legs of an EE core geometry.
3. A zero-sequence blocking transformer as claimed in claim 1 , further comprising a fourth core part as a fourth leg of the transformer, and a fourth pair of windings formed on the fourth leg.
4. A multi-phase auto-transformer rectifier unit comprising:
a plurality of diode bridge rectifiers connected in parallel;
a DC-link capacitor between the rectifiers and a load to be driven, in use, by the unit; and
a zero-sequence blocking transformer as claimed in claim 1 between the rectifiers and the DC-link capacitor.