Generator Main Field Energy Extraction Circuit
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Solution Overview
Problem
Conventional generators face challenges in quickly dissipating the main field energy during a load fault, leading to prolonged current flow and potential overheating, which can cause damage and safety hazards.
Innovation Solution
A system and method involving a controller and energy dissipator circuit that reroutes the main field current through a high-resistance dissipator during a load fault, significantly reducing the time constant of the main field current and facilitating quick fault clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the exciter current is turned off during a load fault, then the generator controller attempts to limit the energy delivered into the fault, but the rotor magnetic field does not immediately fall to zero due to the stored magnetic energy and the relatively long L/R time constant, causing the field current to free-wheel through the rotor components and the main armature to continue producing current
Solution Approach 1:
The patent extracts the main field current from its normal circulation path through the rotor components and main armature, and redirects it through a dedicated dissipator circuit. This extraction allows the magnetic energy to be deliberately discharged through a controlled path with appropriate resistance, significantly reducing the L/R time constant and accelerating the decay of the main field current during fault conditions.
Solution Approach 2:
The dissipator circuit acts as an intermediary element between the main field winding and the rest of the generator system. This mediator provides a controlled resistance path that enables rapid dissipation of magnetic energy without directly affecting the normal operation of the rotor components and main armature during healthy conditions.
2Productivity
If the main field current continues to flow during a load fault, then the main armature continues producing current to the short-circuit, compounding the problem and making it difficult to clear the fault, but turning off the exciter current alone is insufficient due to the long L/R time constant
Solution Approach 1:
The patent implements preliminary action by preparing a dissipator circuit with appropriate resistance values before fault conditions occur. When a fault is detected, the system can immediately redirect the main field current through this pre-configured dissipator path, eliminating the delay associated with attempting to rely on natural decay or attempting to quickly switch off exciter current alone.
Solution Approach 2:
The patent changes the electrical parameters of the main field circuit during fault conditions by introducing a controlled resistance through the dissipator. This parameter change (adding resistance to the circuit) directly reduces the L/R time constant, transforming the slow-decaying magnetic field into a rapidly dissipating one, thereby reducing both the duration and harmful effects of fault current.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces the duration and amplitude of the main field current, protecting generator components, ensuring safe shutdown and fault clearance, and reducing the risk of damage and fire hazards.
Implementation Method 1
an energy dissipator, with a first end and a second end, to dissipate energy from the system
Implementation Method 2
A magnetic field on the spinning rotor, generated by a current passing through the rotor winding, induces an electrical current in the windings of the stator creating AC electricity
Data Source
AI summary
A system and method for controlling the main field current in an electrical generator is disclosed. The system can include a controller to sense the voltages and currents in the system to identify load faults. The system can also comprise one or more switches and an energy dissipator to absorb, store, or dissipate the main field current in the event of a load fault, such as a short circuit. In the event of a load fault, the controller can change the position of the one or more switches to redirect the main field current from the main field windings of the rotor to the energy dissipator. The energy dissipator can absorb or store the main field current significantly reducing the time required to stop the output current of the generator.