Electricity: single generator systems – Generator control – With excitation winding and/or circuit control
Reexamination Certificate
1999-05-03
2001-03-27
Ponomarenko, Nicholas (Department: 2834)
Electricity: single generator systems
Generator control
With excitation winding and/or circuit control
C322S061000
Reexamination Certificate
active
06208120
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains generally to excitation control systems for rotating electrical apparatus and, more particularly, to such systems employing rectifiers, such as three-phase semiconductor controlled rectifier (SCR) bridges, for converting alternating current (AC) to direct current (DC) to provide excitation voltage to a generator.
2. Background Information
Three-phase rectifier circuits are commonly employed to convert AC signals to DC signals. These circuits often use SCRs disposed in bridge segments, with typically one SCR for each polarity of each AC phase. Typically, a bridge firing control circuit controls the firing point for each rectifier in each AC cycle.
It is not uncommon for a plurality of SCR bridges to be operated in parallel with each of the corresponding bridge firing control circuits being controlled by a central firing control circuit. The central firing control circuit manages each of the bridge firing control circuits in order that the corresponding rectifiers in each of the parallel bridges conduct current at the same point in the AC waveform.
SCR bridges are commonly employed in an excitation control system to provide field excitation for a rotating electrical apparatus (e.g., large synchronous generators and motors, utility synchronous generators and motors, industrial synchronous motors and generators, synchronous generators and motors for naval or other shipping applications, synchronous generators and motors for oil well drilling rigs). For example, when the generator, is on-line, generator field excitation is provided thereto. However, certain faults in the output power circuit of the generator may disturb the voltage fed into the excitation control system, thereby causing the excitation to the generator to shut off.
For example, disturbances in the input voltage to the phase lock loop (PLL) of the control system may be caused by faults, such as single line-to-ground faults, line-to-line faults and three-phase faults that occur in the power circuit when the generator's circuit breaker contacts are closed. Accordingly, there is room for improvement.
SUMMARY OF THE INVENTION
The present invention provides improvements in the operation of an excitation control system for a rotating electrical apparatus, such as a generator. Normally, each of the segments of a controlled rectifier bridge responds to a control signal in order to control current conduction within the segments between the input and output of the controlled rectifier bridge. Whenever an alternating current phase error signal exceeds a predetermined value, the maximum value of the excitation voltage is requested for the rotating electrical apparatus, and the rotating electrical apparatus is on-line or connected to its power circuit, the control signals are repetitively and simultaneously output to each of the segments in order that the controlled rectifier bridge emulates a diode bridge.
As one aspect of the invention, an excitation control system for a rotating electrical apparatus comprises a controlled rectifier bridge including an input interconnected with a plurality of alternating current phases each of which has a positive polarity and a negative polarity, an output interconnected with the input of the rotating electrical apparatus in order to provide an excitation voltage thereto, and a segment for each of the positive and negative polarities of the alternating current phases, with each of the segments having an element responsive to a control signal in order to control current conduction within the segment between the input and the output of the controlled rectifier bridge. A means requests a maximum value of the excitation voltage for the rotating electrical apparatus. A means determines when the rotating electrical apparatus is on-line. A means provides an error signal from the alternating current phases. A means outputs the control signals to the segments in order to control current conduction within the segments and includes means for repetitively and simultaneously outputting the control signals to each of the segments in response to: (a) the error signal exceeding a predetermined value, (b) the maximum value of the excitation voltage for the rotating electrical apparatus is requested by the means for requesting; and (c) the means for determining determines the rotating electrical apparatus is on-line, in order that the controlled rectifier bridge emulates a diode bridge.
As another aspect of the invention, an excitation control system for a rotating electrical apparatus comprises a transformer including a plurality of primary windings interconnected with alternating current phases and also including a plurality of secondary windings having a plurality of alternating current phases each of which has a positive polarity and a negative polarity. At least one controlled rectifier bridge includes an input interconnected with the alternating current phases of the secondary windings of the transformer, an output interconnected with an input of the rotating electrical apparatus in order to provide an excitation voltage thereto, and a segment for each of the positive and negative polarities of the alternating current phases of the secondary windings, with each of the segments having an element responsive to a control signal in order to control current conduction within the segment between the input and the output of the controlled rectifier bridge. A means regulates the output of the rotating electrical apparatus and includes an output having a signal which requests a maximum value of the excitation voltage for the rotating electrical apparatus. A means connects and disconnects the output of the rotating electrical apparatus to a power circuit and includes an output having a signal which indicates that the rotating electrical apparatus is connected to the power circuit. A means provides an error signal from the alternating current phases of the secondary windings of the transformer. A means outputs the control signals to the segments in order to control current conduction within the segments and includes means for repetitively and simultaneously outputting the control signals to each of the segments in response to: (a) the error signal exceeding a predetermined value, (b) the output of the means for regulating having the signal which requests the maximum value of the excitation voltage for the rotating electrical apparatus, and (c) the output of the means for connecting and disconnecting having the signal which indicates that the rotating electrical apparatus is connected to the power circuit, in order that the controlled rectifier bridge emulates a diode bridge.
REFERENCES:
patent: 4152636 (1979-05-01), Gorden
patent: 4463306 (1984-07-01), De Mello et al.
patent: 4723106 (1988-02-01), Gibbs et al.
patent: 4741023 (1988-04-01), Lawson
patent: 4855664 (1989-08-01), Lane
patent: 5440222 (1995-08-01), Tanaka et al.
patent: 5483147 (1996-01-01), Ilic et al.
patent: 5594322 (1997-01-01), Rozman et al.
patent: 5694027 (1997-12-01), Satake et al.
patent: 5698968 (1997-12-01), Takagi et al.
patent: 5963440 (1999-10-01), Gibbs et al.
patent: 5963441 (2000-04-01), Gibbs et al.
patent: 6046917 (2000-04-01), Gibbs et al.
Eaton Corporation
Moran Martin J.
Ponomarenko Nicholas
LandOfFree
Excitation control system for rotating electrical apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Excitation control system for rotating electrical apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Excitation control system for rotating electrical apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2441907