Fast de-excitation brushless exciter
AssigneeWestinghouse Electric Corp.
InventorDale I. Gorden
Life of this patent
Estimating the term…
Abstract
Thyristors are substituted for conventional diodes in the rotating rectifier assembly of a brushless exciter in a synchronous dynamoelectric machine. In contrast with prior systems in which thyristors are switched at relatively high ceiling voltages (requiring thyristors of high power rating and additional components for fast de-excitation), the gates of the thyristors in the present invention are fired only at a low voltage point of the negative half cycle of the polyphase armature voltage waveforms for fast de-excitation and are maintained in a fully conducting condition during the positive half cycle. This permits the use of thyristors having a relatively lower power rating and makes unnecessary additional components to achieve fast de-excitation.
Claims5
In combination,
- a synchronous dynamoelectric machine having a stator member carrying an alternating current armature winding and a rotor member carrying a direct current field winding;
- a main exciter for said synchronous dynamoelectric machine having a stator member carrying the field winding and a rotor member carrying a polyphase armature winding;
- a rectifier assembly having an input circuit connected to receive alternating current power from said main exciter armature and an output circuit connected to conduct direct current excitation through said synchronous machine rotor field winding, said rectifier assembly comprising:
- a plurality of controlled rectifier elements electrically connected in bridge relation between each phase of said polyphase armature winding and said output circuit to conduct current, when gated on, from associated phases of said polyphase armature winding to said direct current field winding of said synchronous dynamoelectric machine;
- means operable to provide a control signal in response to a predetermined loading condition of said synchronous dynamoelectric machine;
- means responsive to a predetermined function of said control signal connected to control the gating of said controlled rectifiers, said controlled rectifiers being maintained thereby in a fully conducting condition with said rectifier elements being rendered conductive only during the positive half cycle of the voltage waveform of respective associated input phases during starting, operation at rated load, and operation at a load level exceeding rated load in a forcing mode of operation, and said controlled rectifier being maintained in a conducting condition with said rectifier elements being rendered conductive only during the negative half cycle of the respective voltage waveform associated with each phase of said armature winding thereby providing fast de-excitation of said synchronous dynamoelectric machine upon the occurrence of a predetermined overload condition.
In a method of developing direct current excitation for the field winding of a synchronous dynamoelectric machine in which polyphase alternating current induced in a rotating exciter armature is rectified by a plurality of controlled rectifier elements electrically connected in a bridge arrangement to conduct current, when gated on, from said armature to said field winding, the improvement comprising:
- maintaining said controlled rectifier elements in substantially full conducting condition during the positive half cycle of the voltage waveform of each associated armature winding phase during starting, operation at rated load, and operation at a load level exceeding rated load in a forcing mode of operation;
- and,
- gating said controlled rectifier elements to a conducting condition with said controlled rectifier elements being rendered conductive only during the negative half cycle of the voltage waveform associated with each phase of said armature winding thereby providing fast de-excitation of said synchronous dynamoelectric machine.
Dependencies are inferred from the claim text.