Generator Overheating Protection via Dynamic Excitation Current Offset
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Solution Overview
Problem
Existing methods for protecting motor vehicle generators from overheating are imprecise due to differences in thermal time constants between the generator regulator and its components, leading to inadequate excitation current adjustments and potential damage or unnecessary power loss.
Innovation Solution
The method involves determining a dynamic offset of the excitation current over time, which is weighted and potentially delayed, to accurately calculate a computing temperature that shifts the limiting characteristic curve for excitation currents, ensuring effective protection against overheating for components with varying thermal time constants without unnecessarily reducing output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the excitation current is reduced based on regulator temperature alone, then the regulator is protected from overheating, but components with different thermal time constants (generators with longer time constants and rectifiers with shorter time constants) are not adequately protected, leading to potential damage or unnecessary power loss
Solution Approach 1:
The patent segments the temperature protection approach by creating separate temperature models for different components (generator and rectifier) with distinct thermal time constants. Instead of using a single regulator temperature measurement, the system calculates component-specific temperatures TVG(t) and TVR(t) based on their respective thermal characteristics, allowing each component to be protected according to its unique thermal behavior.
Solution Approach 2:
The patent applies preliminary action by calculating the dynamic offset dIE/dt in advance and using it to adjust the excitation current before actual overheating occurs. The system continuously monitors the rate of change of excitation current and proactively adjusts the current limits based on predicted temperature trends, preventing overheating rather than reacting after it occurs.
2Reliability
If the excitation current is continuously reduced to prevent overheating, then component temperatures are kept safe, but the output voltage and power output are unnecessarily reduced, leading to power loss
Solution Approach 1:
The patent applies dynamics by implementing time-dependent excitation current limits IE_limit(t) that adapt to the actual thermal state of components. Instead of using fixed conservative limits, the system dynamically adjusts the current limits based on real-time temperature calculations, allowing maximum power output when components are cool and reducing current only when and where thermal limits are approached.
Solution Approach 2:
The patent changes the parameter of excitation current limits from static values to dynamic time-dependent values IE_limit(t). The system continuously updates the current limits based on the calculated temperatures and thermal time constants, optimizing the balance between component protection and power output by adjusting the current parameter in response to changing thermal 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
This approach precisely determines the computing temperature for stable and transient states, preventing overheating and minimizing power losses by optimizing excitation current adjustments, effectively protecting both components with longer and shorter thermal time constants than the regulator.
Implementation Method 1
The voltage regulator regulates the output voltage of the generator by influencing the excitation current
Implementation Method 2
The time profile of the temperature is formed by evaluating a change in resistance or by evaluating the temperature of a temperature-dependent resistor
Implementation Method 3
the course of the temperature over time can also be formed by evaluating the heating of a semiconductor path, in particular a Zener diode
Data Source
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AI summary
The invention relates to a method for protecting a motor vehicle generator from overheating, wherein a specified limiting characteristic curve, relating to a base temperature and describing a maximally allowable exciting current value, is shifted in dependence on a computed temperature, a static offset is determined in a first step and a dynamic offset is determined in a second step upon determination of the computed temperature, the static offset is determined in dependence on the exciting current and the dynamic offset is determined as a derivation of the exciting current over time.