Patent ID: 6856230
Filing Date: 2005-02-15
Classification: H01F,H02J,H03H,Y02E

Abstract:
1. A filter to remove harmonics comprising: (a) an autotransformer with a ferromagnetic core having a plurality of legs forming a low-reluctance flux path, a first bar forming the low-reluctance flux path between the legs at one end of the core, and a second bar forming a low-reluctance flux path between the legs at the other end of the core; (b) first and second coils, having first and second terminals, the first and second coils being spaced apart at a first location on one of the legs; (c) an electrical connection between the second terminal of the first coil and the first terminal of the second coil, “whereby the first and second coils are in a series input circuit to receive the alternating current to be filtered, said current generating flux in the first leg”; (d) a filter output terminal; (e) means to connect the electrical connection to the output terminal; (f) a region of increased reluctance in a part of the flux path linking the second coil, thereby forming a built-in inductor in the second coil; (g) magnetic shunt means which magnetically couples one of the legs at a third location between the first and second locations to an adjacent one of the legs where some of the flux generated by alternating current flowing in the first coil is by-passed through the shunt means to the adjacent leg without linking with the second coil; and (h) capacitor means connected across the second coil to resonate with the built-in inductor at the fundamental frequency.