Variable leakage transformer

• US 4,327,348 A
• Filed: 10/03/1979
• Issued: 04/27/1982
• Est. Priority Date: 05/20/1977
• Status: Expired due to Term

• Current Assignee: TDK Corporation
• Original Assignee: TDK Electronics (TDK Corporation)
• Inventors: Hirayama, Hiromitsu
• Primary Examiner(s): Pellinen, A. D.
• Application Number:
  US06/081,339
• Time in Patent Office: 937 Days
• Field of Search: 323/48, 323/56, 323/249, 323/250, 323/254, 323/262, 323/329, 323/331, 323/338, 323/339, 336/160, 336/165, 336/178, 336/184, 336/212, 336/215
• US Class Current: 336/184
• CPC Class Codes: H01F 2029/143 with control winding for generating magnetic bias
• CPC Class Codes: H01F 29/14 with variable magnetic bias amplitude modulation by means of variable impedance element H03C1/08 ; magnetic amplifiers H03F; circuits for automatic telephonic communication H04M3/00

Abstract

A variable leakage transformer or a variable voltage transformer comprising a magnetic core with a main-magnetic path and a sub-magnetic path, the main magnetic path having at least a common magnetic path with the submagnetic path, a primary winding wound on said common magnetic path of the core, a secondary winding wound on said main magnetic path of the core, means for controlling the magnetic flux in said sub-magnetic path, and said main-magnetic path having a thin air gap. By controlling the magnetic flux in the sub-magnetic path, the leakage of the flux induced by the primary winding from the main-magnetic path to the sub-magnetic path can be controlled. Thus the coupling between the primary and secondary windings, and conduction period in each cycle of the AC output voltage are controlled. The control of the conduction period in each cycle provides the control of the power transmitted from the primary winding to the secondary winding. Because of the presence of the air gap provided in the main-magnetic path, excellent control of the output voltage is obtained even when a load is small.

Claims

1. A variable leakage transformer comprising of a first closed magnetic path having a U shaped core and an I shaped core, a second closed magnetic path having an E shaped core and an I shaped core, the center leg of said E shaped core being connected to one leg of said U shaped core, a pair of spacers of non-magnetic material inserted between the top of the legs of said U shaped core and the related I shaped core, said U shaped core and the relating I shaped core constituting the main magnetic path and said E shaped core and the relating I shaped core constituting the sub-magnetic core, a primary winding wound common to the center leg of said E shaped core and one leg of said U shaped core, a secondary winding wound on the other leg of said U shaped core, and a pair of control windings wound on the pair of side legs of said E shaped core and being connected in series with each other.

2. A variable leakage transformer according to claim 1, wherein said cores are made of ferrite, and at least a part of said primary winding is wound on the same leg of said U shaped core as that on which the secondary winding is provided.

3. A variable leakage transformer, comprising:

(a) a closed main magnetic path made of ferromagnetic material;

(b) a pair of closed sub-magnetic paths made of ferromagnetic material having a common portion;

(c) said common portion of the sub-magnetic paths coinciding with a part of the main magnetic path to provide a common magnetic path;

(d) a primary winding wound on said common magnetic path;

(e) a secondary winding wound on said main magnetic path;

(f) a pair of control windings wound on respective ones of said sub-magnetic paths and connected in series with each other;

(g) said primary winding being divided into a first primary winding portion and a second primary winding portion, said first primary winding portion being wound on the common magnetic path, and said second primary winding portion being wound on the main magnetic path in closely coupled magnetic relationship with the secondary winding,

(h) the sub-magnetic paths being symmetrically arranged with respect to the main magnetic path, and

(i) a small magnetic gap being provided in the main magnetic path, and the sub-magnetic paths being completely closed without any magnetic gap therein.

4. A variable leakage transformer according to claim 3, wherein said gap comprises a spacer made of non-magnetic material.

5. A variable leakage transformer according to claim 3, wherein said ferromagnetic material has a characteristic such that the ratio of (i) the magnetic permeability thereof when the magnetic flux therein is high to (ii) the magnetic permeability thereof when the magnetic flux therein is low, is large.

6. A variable leakage transformer according to claim 3, wherein said ferromagnetic material comprises a ferrite.