Direct current measuring system for rectifiers
AssigneeGeneral Electric Company
InventorsJames G. Jewell, Fred W. Kelley, Jr., Charles H. Titus
Life of this patent
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Abstract
A DC measuring circuit for power rectifiers is described wherein primary line current is utilized to measure direct current output. In the measuring circuit line current transformers are connected to a multiphase instrument rectifier through a phase shifting current transformer which is adjustable to compensate for difference between the primary to secondary line current phase shift characteristic of the power transformer and any phase shift in the line current transformers. By such compensation the average value of rectified primary line current in the measuring circuit is maintained independent of the commutating angle of the rectified power current.
Claims13
In a system for measuring the magnitude of direct output current from a multiphase power rectifier having an input circuit including a multiphase power transformer, said power transformer having primary and secondary phase windings connected to provide a phase shift between the multiphase primary and secondary line currents coupled by said power transformer, the combination which comprises line current transformers for measuring each said primary line currents, said line current transformers having secondary windings each connected at one end to a common neutral terminal, a phase shifting current transformer comprising primary and secondary phase windings coupled by separate magnetizable cores in each phase, said cores being designed for normal operation below saturation, means connecting said line current transformer secondary windings to the primary windings of said phase shifting current transformer, said phase shifting transformer providing a primary to secondary winding current phase shift vectorially equal to the current phase shift in said power transformer, a multiphase instrument rectifier connected to the secondary windings of said phase shifting current transformer, and a direct current measuring instrument connected to the output terminals of said instrument rectifier.
In a system for measuring the magnitude of direct output current from a multiphase power rectifier having an input circuit including a multiphase power transformer, said power transformer having primary and secondary phase windings connected to provide a phase shift between the multiphase primary and secondary line currents coupled by said power transformer, the combination which comprises line current transformers for measuring said primary line currents, said current transformers having secondary windings each connected at one end to a common neutral terminal, a current autotransformer comprising primary and secondary phase windings one of which is defined in each phase by an intermediate tap terminal on the other, said primary and secondary phase windings of said autotransformer being coupled by separate magnetizable cores in each phase and said cores being designed for normal operation below saturation, means connecting said line current transformer secondary windings to the primary windings of said current autotransformer, said tap terminals being positioned to provide a primary to secondary winding current phase shift in said autotransformer vectorially equal to current phase shift in said power transformer, a multiphase instrument rectifier connected to the secondary windings of said autotransformer, and a direct current measuring instrument connected to the output terminals of said instrument rectifier.
In a system for measuring the magnitude of direct output current from a multiphase power rectifier having an input circuit including a multiphase power transformer, said power transformer having primary and secondary phase windings connected to provide a phase shift between the multiphase primary and secondary line currents coupled by said power transformer, the combination which comprises line current transformers for measuring each said primary line currents, a phase shifting current transformer comprising primary and secondary phase windings coupled by separate magnetizable cores in each phase, said cores being designed for normal operation below saturation, means connecting said line current transformer secondary windings to the primary windings of said phase shifting current transformer, said phase shifting transformer providing a differential primary to secondary winding current phase shift vectorially equal to the difference between current phase shift in said power transformer and said line current transformers, a multiphase instrument rectifier connected to the secondary windings of said phase shifting current transformer, and a direct current measuring instrument connected to the output terminals of said instrument rectifier.
Dependencies are inferred from the claim text.