Electricity: single generator systems – Generator control – With excitation winding and/or circuit control
Reexamination Certificate
1999-12-13
2001-05-15
Ponomarenko, Nicholas (Department: 2834)
Electricity: single generator systems
Generator control
With excitation winding and/or circuit control
C322S037000
Reexamination Certificate
active
06232751
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 which 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.
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 generators and motors, 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. Whenever the generator is on-line and providing power to a load, the generator circuit breaker is closed. An auxiliary contact of the generator circuit breaker is employed to indicate the closed or open status of the breaker and, thus, the on-line or off-line status, respectively, of the generator. In turn, generator tripping logic or protection logic employs this closed or open status to adjust trip thresholds in the trip logic or to adjust limiters in the protection logic.
If the auxiliary contact erroneously indicates an off-line status for an on-line generator, then the trip or protection logic may cause a reduction of excitation to the online generator and, thus, cause it to improperly enter the off-line state, thereby interrupting power to the load and adversely impacting the availability of the generator.
Accordingly, there is room for improvement.
SUMMARY OF THE INVENTION
The present invention provides improvements in an excitation control system for a rotating electrical apparatus. An electrical signal related to the output of the rotating electrical apparatus is provided. A validation signal, which is representative of the rotating electrical apparatus having an on-line state, is provided when the electrical signal is greater than a predetermined signal. In turn, the validation signal is employed by protection logic or tripping logic for the rotating electrical apparatus.
In accordance with one aspect of the invention, an excitation control system includes means for providing an excitation voltage to the input of a rotating electrical apparatus; means for regulating the excitation voltage; means for providing an electrical signal related to the output of the rotating electrical apparatus; means for providing a logic signal having a first state when the electrical signal is greater than a predetermined signal and the rotating electrical apparatus is in an on-line state, with the logic signal otherwise having a second state; means employing the first state of the logic signal for providing online protection or trip parameters, and employing the second state of the logic signal for providing off-line protection or trip parameters; and means employing said protection or trip parameters for protecting or tripping the rotating electrical apparatus.
As another aspect of the invention, the signal of the output of the circuit breaker for a rotating electrical apparatus is qualified with a validation signal and the qualified signal is employed for protecting or tripping the rotating electrical apparatus. In particular, an excitation control system for the rotating electrical apparatus includes an input responsive to an excitation voltage, an output having at least one alternating current phase, and a circuit breaker for such at least one alternating current phase. The circuit breaker includes an output having a signal with a first state when the circuit breaker is closed and the rotating electrical apparatus is on-line, and with a second state when the circuit breaker is open and the rotating electrical apparatus is off-line. The excitation control system includes means for providing the excitation voltage to the input of the rotating electrical apparatus; means for regulating the excitation voltage; means for providing an electrical signal related to the output of the rotating electrical apparatus; means for providing a validation signal when the electrical signal is greater than a predetermined signal; means for qualifying the signal of the output of the circuit breaker with the validation signal and providing a qualified signal therefrom; and means employing the qualified signal for protecting or tripping the rotating electrical apparatus.
REFERENCES:
patent: 3936722 (1976-02-01), Goto et al.
patent: 5440222 (1995-08-01), Tanaka et al.
patent: 5483147 (1996-01-01), Llic et al.
Farr Lawrence B.
Gibbs Irving A.
Morse Charles A.
Mummert Charles R.
Eaton Corporation
Moran Martin J.
Ponomarenko Nicholas
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