A reliable high-powered constant current supply

Abstract

The use of series-connected saturable reactors operating in the constrained mode has proven to be a reliable and trouble-free means for developing constant current power such as that required by transoceanic cable systems. As the art has progressed towards the use of higher and higher ac power frequencies, however, it has become increasingly difficult to design a single ac power source of substantial power rating without resorting to rather complex and inefficient circuitry. In practice, the saturable reactors are used in conjunction with transformers. This paper demonstrates that by departing from convention in the design of the saturable reactor and output transformer, it is possible, using a single reactor and transformer, to combine the outputs from a multiplicity of ac power sources or converter stages on a load sharing basis so as to obtain a single supply with the required power rating. The particular arrangement of the specially designed saturable reactor and output transformer permits a unique interaction to be established in which the two complement one another; the reactor controlling the summation of source currents to achieve output regulation and the transformer proportioning these currents among the sources to insure proper sharing of load power. Variations in load power are automatically accompanied by a shift in the operating power factor of the individual sources. Also, because the method affords electrical isolation, sources of unequal current, voltage, and power ratings can readily be combined. Furthermore, this technique permits the use of excess (redundant) ac sources so that normal operation can be maintained following the loss of output from any one of the sources.