Standard configuration a.c. power transformer core sections are combined with standard configuration solenoid winding sections to provide a saturable core transformer which is arranged to be driven into saturation by applied alternating and direct current energy with the control of variations in flux changes up to saturation exercised by the direct current flow. A center tapped primary winding is arranged on an I- shaped stack of transformer iron laminations for full-wave excitation. A C-shaped stack of laminations is arranged adjacent to the I-shaped stack and separated by an air gap whereby the primary winding also serves as an input filter choke. The core structure is completed by an E-shaped stack of laminations arranged adjacent to the I-shaped stack and separated by another air gap. Two solenoid windings are arranged on the outer legs of the E-shaped stack and connected to a capacitor for resonating the overall ferroresonant transformer circuit arrangement. Secondary windings are also arranged on the outer legs and connected to a rectifying circuit for supplying direct potential to a load. A control winding is arranged on the central leg of the E-shaped stack of laminations. With this arrangement, the control winding is unaffected by variations in the a.c. voltage as they affect the flux changes in the transformer or in the frequency of the a.c. Regulation of the power supply is executed by direct current flow in the control winding. An adjustable resistor connecting the control winding across the output of the rectifier circuit is often all that is required to complete the circuit. In some applications, an amplifying circuit is used to provide a desired gain in the control winding circuitry.
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