Downhole Generator Assembly With Exciter for Higher Power Output
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Solution Overview
Problem
Downhole generators in wellbores face limitations in power output due to size constraints and space limitations, which restrict the rotational frequency of rotors and magnetic fields, affecting the efficiency and stability of power generation.
Innovation Solution
A generator assembly configuration that includes a first generator for power output and a second generator acting as an exciter to increase the magnetic field of the first generator's rotor, enhancing power output without increasing the assembly's size or rotational frequency, using fluid flow to rotate turbines and induce currents in stators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the size of the generator assembly is increased to improve power output, then the power output capability increases, but the space constraints in the wellbore are violated
Solution Approach 1:
The patent changes the magnetic field parameter by introducing a separate exciter generator that provides controlled magnetic flux to the main generator's rotor. This allows the main generator to operate at higher power output without increasing its physical size, as the magnetic field strength is optimized through external excitation rather than relying solely on permanent magnets or larger rotor volume.
Solution Approach 2:
The exciter generator serves multiple functions: it generates power for downhole tools and simultaneously provides the magnetic field excitation for the main generator. This multi-functionality allows the system to achieve higher power output from the main generator without adding separate excitation equipment, thereby avoiding increased overall assembly size.
2Power
If the rotational frequency of the rotor is increased to improve power output, then the power generation efficiency increases, but the stability of the generator assembly deteriorates
Solution Approach 1:
The exciter generator creates a controlled feedback loop where the magnetic field strength is regulated based on the operational requirements of the main generator. This feedback mechanism allows the system to maintain optimal magnetic flux levels that support higher rotational frequencies and power output while preventing instability through active control of the excitation field.
3Power
If the magnetic field strength is increased to improve power output, then the induced current in the stator increases, but the energy consumption increases
Solution Approach 1:
The exciter generator is driven by the same fluid flow that drives the main generator's turbine, utilizing the available kinetic energy in the fluid stream. The exciter converts a portion of this fluid energy into electrical energy to power the rotor's magnetic field, making the system self-sufficient for excitation needs without requiring additional external energy input.
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
This configuration effectively increases power output to downhole tools without enlarging the generator assembly or increasing rotational frequency, ensuring stability and efficiency in power generation for controlling fluid flow in wellbores.
Implementation Method 1
The rotor may include a permanent magnet that, when rotated via the fluid flow, may induce a current in a stator due to the magnetic field of the rotor interacting with the stator, and thus outputting power from the stator of the generator to the downhole tool.
Implementation Method 2
The fluid flow may rotate a turbine in the generator assembly, thus rotating a rotor.
Data Source
AI summary
An apparatus configured to be positioned on a tubular string in a wellbore formed in a subsurface formation. The apparatus comprises a generator assembly disposed on the tubular string and configured to output power to a downhole tool. The generator assembly includes a first generator configured to output a first power to the downhole tool. The generator includes a second generator configured to function as an exciter for the first generator.