Resonant commutation system for exciting a three-phase alternator

摘要

An alternator has a field coil that produces a magnetic field which induces electricity in a coil arrangement. A field coil excitation system includes a generator with an output coil assembly for producing alternating electricity. A rectifier converts the alternating electricity into voltage and direct current at two nodes. A capacitor, between the nodes, has capacitance that forms a resonant circuit with inductance of the output coil assembly. Due to that resonant circuit, the voltage and direct current oscillate in a predefined phase relationship. A switch and the field coil are connected in series between the nodes. A controller renders the switch conductive for a time period specified by a received control signal. The switch is rendered non-conductive at the first occurrence of a minimum current level after the time period ends. The predefined phase relationship enables the minimum current level to be detected by sensing the voltage.

主权项

1. A system for exciting a field coil of an alternator in order to produce a magnetic field that induces electricity in an alternator output coil assembly, the system comprising:
a generator that has an excitation output coil assembly for producing alternating electricity; a rectifier having an input coupled to the excitation output coil assembly and an output, converting the alternating electricity into a direct current with an output voltage, and providing the direct current at the output; a capacitor connected to the output of the rectifier and having a capacitance that forms a resonant circuit with inductance of the excitation output coil assembly, wherein the resonant circuit causes the output voltage and direct current to vary cyclically; a switch connected in series with the field coil, the switch being operable to control application of the direct current to the field coil; a minimum current detector coupled to the output of the rectifier and operable to determine when the magnitude of the direct current is at a minimum level and in response thereto producing an indication; and a controller coupled to a control terminal of the switch and an output of the minimum current detector, the controller,
in response to an excitation control signal, places the switch in a conductive state in which the direct current is applied to the field coil, and,in response to the indication received from the output of the minimum current detector, places the switch in a non-conductive state.