Supply Line Current Limiting for Vehicle Voltage Stability
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Solution Overview
Problem
In onboard vehicle electrical networks, high currents due to low voltage and resistances lead to significant voltage drops, potentially causing functional limitations or deactivation of electrical devices, especially during critical operations like braking.
Innovation Solution
A method to limit load current in a supply line by defining distinct time intervals with different maximum current values, ensuring a minimum terminal voltage for primary devices and maintaining functionality of secondary devices by adjusting current levels based on resistance measurements and voltage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current limiting is designed to maintain minimum terminal voltage for primary devices, then functionality of primary devices is preserved, but performance of primary devices is reduced
Solution Approach 1:
The current limiting is designed dynamically with two distinct time intervals: a first time interval allowing higher current for primary device performance, and a second time interval limiting current to maintain minimum voltage for both primary and secondary devices. This dynamic adjustment resolves the contradiction by providing high power when needed while ensuring reliability through voltage maintenance in critical periods.
Solution Approach 2:
The system performs preliminary current limiting actions by defining current limits for two time intervals before critical voltage drops occur. The first time interval current limit is set to allow optimal primary device performance, while the second time interval current limit is predetermined to maintain minimum terminal voltage, preventing functionality loss before it occurs.
2Power
If high current is supplied to primary load, then power delivery to primary device is maximized, but voltage drop increases causing terminal voltage to fall below minimum levels
Solution Approach 1:
The current limiting applies different current thresholds dynamically: a first current limit during the first time interval that allows high power delivery to the primary load, and a second current limit during the second time interval that ensures terminal voltage remains above minimum levels. This dynamic approach maximizes power when acceptable while preventing voltage collapse.
Solution Approach 2:
The system changes the current parameter over time by implementing two distinct current limits corresponding to two time intervals. The first current limit permits higher current for maximum power delivery, while the second current limit reduces current to maintain acceptable terminal voltage levels, thus managing the trade-off between power and voltage stability.
3Reliability
If current is limited to maintain terminal voltage, then functionality of secondary devices is maintained, but current available to primary device is reduced
Solution Approach 1:
The system performs preliminary current limiting by establishing a second time interval with a specific current limit before voltage drops cause secondary device malfunction. This preliminary action ensures that when the second time interval current limit is applied, secondary devices remain functional while primary device current is appropriately managed.
Solution Approach 2:
The current limiting transitions dynamically from the first time interval (higher current for primary device) to the second time interval (lower current to protect both primary and secondary devices). This dynamic switching ensures secondary device functionality is maintained in the second interval while allowing optimal primary device performance in the first interval.
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 maintains the functionality of both primary and secondary devices by preventing voltage drops below a minimum level, ensuring essential operations like braking are maintained while allowing higher performance when necessary, even at the cost of reduced primary device performance.
Implementation Method 1
there are electrical resistances due to, for example, electrical lines or contacts. When a current flows through such resistances, there is a voltage drop over the resistances
Data Source
AI summary
A method is provided for limiting a load current in a supply line that supplies a first load with electrical current. The method includes: defining a first time interval and a second time interval, the first time interval beginning after a time of connection of the first load to the supply line, and the second time interval beginning later than the first time interval; limiting the load current within the first and second time interval to a first value; limiting the load current, at least at the end of the second time interval, to a second value, the second value being smaller than the first value.