| 摘要 |
A power unit is provided which is capable of controlling electric current to be supplied to a load connected to the power unit, in a flexible manner in dependence on a load condition. Postive and negative converters of a cycloconver are connected to three-phase output windings of a three-phase generator and connected in an antiparallel manner to each other for generating a single-phase alternating current to be supplied to the load. A firing angle control device causes the positive and negative converters to be alternately switched to operate every half a repetition period of the single-phase alternating current, to thereby cause the cycloconverter to generate the single-phase alternating current. A desired wave-forming circuit forms a desired waveform of a drive signal input to the firing angle control device, for causing the firing angle control device to drive the positive and negative converters, such that the output single-phase alternating current has a desired alternating current waveform. An amplitude control circuit changes a shape of the desired waveform in dependence on variation in the load so as to stabilize an output voltage of the cycloconverter. An amplitude-limiting circuit limits amplitude of the desired waveform to a smaller value when the output voltage of the cycloconverter becomes equal to or lower than a predetermined value.
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