Closed-Loop Ferroresonant Power Transformer
Original Publication Date: 1985-Jun-01
Included in the Prior Art Database: 2005-Feb-18
Ferroresonant regulators provide an inexpensive and reliable form of power conversion but have found limited application because of poor load regulation characteristics created by an open-loop operation. U.S. Patent 3,914,685 to B. C. Van Gilder partially overcomes this problem by providing closed-loop regulation by electronically switching a linear inductor across a portion of the resonant winding at predetermined times during each input voltage half cycle. The Van Gilder regulator has a transient response time which is limited to one-half the line frequency and, therefore, is only marginally useful in responding to input voltage variations, such as power line disturbances. The response time can be significantly improved by providing active linear control, such as is shown in the figure.