Generator Excitation Switch-Off Paths for Vehicle Overvoltage Protection
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Solution Overview
Problem
In vehicle generators, overvoltage events can occur due to defective voltage regulators, leading to malfunctions or damage in on-board power supply components, as existing systems lack effective mechanisms to quickly and safely mitigate excessive generator voltage.
Innovation Solution
A safety switch-off arrangement with two redundant switch-off paths is implemented, where the rotor winding is de-excited via a first path and the controller output is short-circuited via a second path, using diodes and a fuse element to dissipate excess current and protect the system from overvoltage, with cascaded triggering and redundant components for enhanced safety integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional voltage regulator is used to control exciter current, then the generator can operate normally with regulated output voltage, but the system lacks sufficient protection against overvoltage events caused by regulator defects
Solution Approach 1:
The safety switch-off arrangement is divided into two independent switch-off paths: a first switch-off path for de-exciting the rotor winding and a second switch-off path for short-circuiting the controller output. This segmentation allows each path to be optimized for its specific function while providing redundant protection against overvoltage events.
Solution Approach 2:
The patent implements beforehand cushioning by providing redundant switch-off paths that are prepared in advance to handle overvoltage events. The first switch-off path with de-excitation diodes and the second switch-off path with short-circuiting capability are pre-configured to activate when voltage exceeds safe thresholds, protecting the system before damage can occur.
2Reliability
If the rotor winding is de-excited quickly to prevent overvoltage damage, then component safety is improved, but additional switch-off paths and components are required
Solution Approach 1:
The protection mechanism is segmented into two distinct switch-off paths with different functions: the first path de-excites the rotor winding by providing an alternative current path through diodes, while the second path directly short-circuits the controller output. This segmentation enables quick response to overvoltage conditions without requiring a single complex switch-off mechanism.
Solution Approach 2:
Diodes are used as intermediary components in the first switch-off path to provide a controlled path for de-exciting current from the rotor winding. These diodes act as mediators that safely dissipate energy and prevent direct damage to sensitive components while maintaining system integrity.
3Reliability
If redundant switch-off paths are implemented to ensure high safety integrity, then overvoltage protection is enhanced, but the device complexity and component count increase
Solution Approach 1:
The redundant protection system is segmented into two independent switch-off paths that can operate autonomously. The first path handles normal overvoltage events through controlled de-excitation, while the second path provides backup protection through direct short-circuiting. This segmentation ensures high safety integrity without requiring a single overly complex mechanism.
Solution Approach 2:
The system uses parameter changes by monitoring voltage levels and automatically switching between different protection modes. When voltage exceeds the first threshold, the first switch-off path activates; when it exceeds the second threshold, the second switch-off path activates. This parameter-based control enables redundant protection with intelligent activation based on actual system conditions.
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 prevents overvoltage damage by quickly de-exciting the rotor winding and short-circuiting the exciter terminal, ensuring high safety integrity and protecting on-board power supplies from generator malfunctions, allowing for modular and retrofittable safety systems that meet various safety requirements.
Implementation Method 1
The diode can be connected in parallel to a switch in the current path of the exciter winding... The current then flows via the diode, where it is dissipated more quickly (or converted into heat).
Implementation Method 2
In any case, however, the short-circuiting is ultimately intended to result in the current to the exciter winding being switched off... an additional fuse element, such as a fuse, which is arranged in the current path of the voltage regulator, is destroyed instead of the voltage regulator.
Data Source
AI summary
A method for operating a generator unit which includes an electric machine which can be connected to an on-board power supply includes steps of, when an exciter voltage is applied to a rotor winding in order to generate an exciter current through the rotor winding and thus to provide an output voltage at a rectifier, a level of the output voltage is determined, wherein the rotor winding is de-excited via a first switch-off path when the output voltage reaches or exceeds a predetermined first safety threshold value for more than a predetermined first safety time, and wherein a controller output to which the rotor winding is connected is short-circuited via a second switch-off path when the output voltage reaches or exceeds a predetermined second safety threshold for more than a predetermined second safety time. The invention also relates to a corresponding safety switch-off arrangement.