Generator Control System for Load-Off Overvoltage Prevention
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Solution Overview
Problem
Existing electrical generators in aircraft and spacecraft face challenges in maintaining precise control of point of regulation (POR) voltage during rapid load-off conditions, leading to potential overvoltage and equipment damage, which necessitates robust and heavy equipment designs to tolerate overvoltage conditions.
Innovation Solution
A control system that utilizes detectors for both POR voltage and rate of change of generator output to initiate field current discharging, allowing for proactive prevention of overvoltage by activating the impedance circuit when a baseline voltage is reached and a threshold rate of change is detected, thereby avoiding the need for POR voltage to exceed its desired level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage-based triggering is used to activate the discharging system, then the system can respond to overvoltage conditions, but the triggering occurs only after POR voltage exceeds the predetermined level, resulting in delayed response and higher peak voltage
Solution Approach 1:
The patent applies preliminary action by detecting the rate of change of POR voltage (dV/dt) in addition to the absolute voltage level. When the rate of change exceeds a threshold, the discharging system is activated before the POR voltage reaches the maximum overvoltage level, enabling proactive prevention rather than reactive correction.
Solution Approach 2:
The patent implements feedback by continuously monitoring both the POR voltage level and its rate of change, then using this information to control the discharging system. The dual-parameter feedback mechanism allows the system to anticipate upcoming overvoltage conditions and respond appropriately, improving both precision and timing.
2Reliability
If the triggering voltage threshold is set higher than the desired POR level to account for time delay, then the system can activate in time, but the POR voltage rises even higher during the time delay period, causing overvoltage conditions
Solution Approach 1:
By monitoring the rate of change of POR voltage, the system takes preliminary action to activate the discharging circuit before the voltage reaches dangerous levels. This anticipatory approach prevents the voltage from rising excessively during the activation time delay, eliminating the need to set the threshold higher than desired POR level.
Solution Approach 2:
The patent applies preliminary anti-action by preparing the discharging system for activation based on the detected rate of change. When dV/dt exceeds the threshold, the system preemptively engages the discharging path, creating an opposing action that counteracts the upcoming voltage rise before it can cause harmful overvoltage conditions.
3Reliability
If robust equipment design is used to tolerate POR overvoltage, then equipment damage is prevented, but equipment size and weight increase
Solution Approach 1:
The generator control system provides self-service by automatically detecting overvoltage conditions through the dV/dt detector and activating the discharging system without external intervention. This self-regulating mechanism prevents overvoltage before it can damage equipment, eliminating the need for heavy protective equipment design.
Solution Approach 2:
The patent introduces an intermediary mechanism (the rate-of-change detector and control system) that mediates between the generator output and the load. This intermediary detects impending overvoltage conditions and activates the discharging path proactively, protecting downstream equipment without requiring the equipment itself to be robust and heavy.
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 solution enables precise control of POR voltage during rapid load-off events, preventing overvoltage conditions and reducing the need for excessive size and weight in equipment, as it activates the impedance circuit before POR voltage rises excessively, ensuring stable operation without equipment damage.
Implementation Method 1
a detector responsive to a rate of change of generator output
Implementation Method 2
this energy contributes to a short-term rise in POR voltage. In the prior art, this residual energy has been discharged into an impedance circuit
Implementation Method 3
the exciter winding current cannot be reduced to zero instantly due to the inductive nature of the winding. A residual amount of energy in an exciter winding
Data Source
AI summary
An electric generator is operated under conditions in which rapid off-loading may occur. A generator control unit (GCU) employs a detector to detect rates of change of output of the generator. In response to a rapid change of output, e.g. an off-loading, an overvoltage protection system is activated. Excess energy stored in an excited winding is directed into an impedance circuit thus precluding overvoltage that may have been produced by the excess energy.