Importance

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Abstract

An uninterrupted AC supply includes an AC to DC converter having several DC storage devices which maintain a constant DC voltage in the event of a failure of several cycles of the AC source. Each of the storage devices is connected to a separate branch circuit. Each branch circuit includes a transistor that is driven in a linear manner during a portion of a quarter cycle of an AC reference source, so that only one branch conducts current at a time. The DC voltage supplied to each branch and the conducting interval of each branch are such that equal energy dissipation occurs in each branch during each quarter cycle. To enable only one set of branches to be used for opposite polarity variations of the AC reference source, the current from all of the branches flows to a single node, then to opposite terminals of a center tapped transformer primary winding via a pair of switches. During first and second opposite polarity half cycles of the AC reference source, the first and second switches are respectively open and closed so that current flows in the transformer winding in opposite directions during the opposite polarity half cycles of the AC reference source. For a sinusoidal source energy dissipation is equalized in each branch by selecting the phase angle, .theta..sub.k, when branch circuit k changes from a conducting to a non-conducting state and the phase angle .theta..sub.k-1 when branch circuit k begins to conduct such that sin.theta..sub.k cos.theta..sub.k-1 -.theta..sub.k -.theta..sub.k-1 /2-1/4(sin2.theta..sub.k +sin2.theta..sub.k-1) is the same for each branch circuit.

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First Claim