North Electric Company

Patrick L Hunter

A regulated voltage converter utilizing an improved method of pulse width modulation is disclosed wherein acceptable current balance and limiting in the converter switching elements are speedily achieved within one half cycle of converter operation. Converter output current is monitored, shaped according to a non-linear transfer function, and integrated to form a voltage signal for comparison with a predetermined reference level. When the integrated signal exceeds the reference level, a control signal is generated to terminate the current pulse in the inverter section of the converter. The inherent balancing and limiting characteristics of this arrangement are easily extended to applications wherein multiple converter stages are paralleled to supply higher power to a common load.

Converter circuit and method having fast responding current balance and

A thyristor controlled ferroresonant voltage regulator in which the output voltage is made adjustable by varying the reset flux level of each of two parallel magnetic core paths upon which the load windings are wound. Decoupling from the alternating current source is provided by a separate inductor. The two core paths are decoupled by magnetic shunts, which provides an inductance which may be designed to obtain a soft commutation characteristic for the ferroresonant capacitor. During one half cycle of the output waveform one thyristor is enabled by an associated control circuit to complete a circuit path for the resonant capacitor through a winding on the second magnetic core path, while the flux in the first magnetic core path is clamped; in the second half cycle, another thyristor is enabled at a time determined by the control circuit, to complete a circuit path for the capacitor through a winding on the first magnetic core path while the flux in the second magnetic core path is clamped.

Variable flux-reset ferroresonant voltage regulator

A transformer-coupled power switching device control arrangement utilizes an active feedback energy source connected to the primary of the coupling transformer to enhance the turn-off drive to the power switching device. The active feedback energy source produces an output directly dependent upon the magnitude of the power switching device output current and independent of the duration of said output current. When the output current drops to zero, the active feedback source is disabled, and a bias network is connected to the transformer primary. The bias network maintains a reverse voltage at the control electrode of the power switching device and establishes a bias current through the primary suitable for resetting the transformer core flux.

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Columbus, OH, United States of America

Patrick L Hunter