US 7,274,574 B1Granted

Magnetically controlled transformer apparatus for controlling power delivered to a load with current transformer feedback

OwnerGeorge E. Biegelinventor

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Abstract

A circuit with a magnetically variable transformer having primary and secondary windings wound on a magnetic core wherein the transformer core with associated windings is placed in close proximity to an independently wound control coil. The transformer core is placed within the bore of the control coil and an optional focusing armature concentrates the magnetic field at the poles. Application of a control current forms poles at the control coil extremities and causes a change in permeability of the transformer core thereby altering the power output of the transformer inversely to the magnitude of the control current. The control current from the output of the secondary coil of a current transformer in series with the load and conditioned by a feedback conditioning circuit modulates the level of the control current. The magnetically variable transformer controls a D.C. to A.C. inverter circuit, which is useful in supplying power to a fluorescent lamp and other A.C. receptive loads. Additionally, a microprocessor optionally modulates the feedback from the secondary of the current transformer while receiving inputs from manual and automatic environmental controls.

A circuit having a variable transformer, a current transformer, and a feedback circuit for supplying a feedback controlled current to a load wherein;

said variable transformer consists of:
a magnetic core upon which is wound at least one primary coil for receiving an input voltage;
said magnetic core additionally having at least one secondary coil for supplying an output voltage proportional to a turns ratio defined by the number of turns of the secondary coil in the numerator to the number of turns of the primary coil in the denominator and a primary current;
said magnetic core being fabricated from a magnetically soft material;
a control coil proximate to and physically isolated from the magnetic core of said variable transformer wherein said physical isolation of said control coil beneficially assures electrical isolation from said primary coil and said secondary coil of said variable transformer;
said control coil receiving a control current from said feedback circuit wherein said control current generates a magnetic field;
said magnetic field causing a change in permeability of the magnetic core of said variable transformer in a physically non-coupled manner wherein said permeability in said magnetic core is increased as said control current in said control coil increases;
said output voltage of said variable transformer decreases with the increase of said permeability;
said current transformer having at least one primary winding and a plurality of secondary windings:
said primary winding of the current transformer receiving a current from the secondary coil of the variable transformer;
wherein
a first secondary winding serving to provide a feedback current to the control coil of said variable transformer;
additional secondary windings being optionally provided for input to one of the group consisting of an external controller, a microprocessor, and a monitoring system;
and
said feedback circuit useful for conditioning said feedback current from said current transformer and being chosen from the group consisting of a DC coupled feedback and control circuit, an AC coupled feedback and control circuit, and an optically coupled microprocessor feedback and control circuit.

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Abstract

Claims8