High-Power Ferroresonant Voltage Regulating Transformers

Two-core Wroblewski ferroresonant transformers up to 25 kVA have been built for 1-phase, and up to 75 kVA for 3-phase, 60-Hz operation. These transformers are used for the isolation, regulation, and transient suppression of line voltage for computers and other data-processing equipment. The transformers have also been used for general service in overseas 50-Hz poorly regulated electric-supply systems. The Wroblewski structure serves for gaseous-discharge lamp ballasts, and more recently for high-power autotransformer or fully isolated output ferroresonant transformers. The butt and spline air gaps are used to adjust the range of input line voltage, the output voltage, and the waveform. The function and interconnection of the windings, the operation of the structures at high and low line-voltage conditions, waveforms and regulation curves will be described.