Pre-charge Resistor Thermal Management via Cycle Counting
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Solution Overview
Problem
Pre-charge components in electric vehicles are prone to overheating due to repeated key cycling, which can lead to damage and increased maintenance costs, as they are designed to handle continuous usage profiles despite being intended for only startup operations.
Innovation Solution
A controller is programmed to selectively connect the pre-charge resistor between the traction battery and electrical impedance, inhibiting connections if a predetermined number of cycles exceed a threshold within a set period, thereby limiting temperature increases and preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-charge components are designed to handle continuous usage profiles to prevent damage during rapid key cycling, then reliability improves, but device complexity and cost increase
Solution Approach 1:
The controller monitors and counts the number of pre-charge contactor closures within a predetermined time period before they occur. By detecting the cycling pattern in advance and comparing it against stored threshold values, the system can prevent overheating damage before it happens, rather than requiring components to be over-engineered for worst-case continuous operation scenarios
Solution Approach 2:
The controller uses feedback from monitoring the pre-charge contactor operation history and compares real-time cycling frequency against predetermined thresholds. When the threshold is exceeded, the controller inhibits further pre-charge operations temporarily, creating a self-regulating system that adapts to actual usage patterns rather than requiring static over-design
2Temperature
If pre-charge components are designed for continuous usage to prevent overheating during rapid key cycling, then temperature control improves, but manufacturing cost increases
Solution Approach 1:
The controller stores predetermined threshold values in memory before operation and uses these pre-calculated limits to control pre-charge contactor closure. This preliminary setup allows the system to maintain safe operating temperatures through software control rather than requiring expensive thermal management hardware or oversized heat-dissipating components
Solution Approach 2:
The controller continuously monitors the number of pre-charge operations and uses feedback control to inhibit further operations when temperature thresholds would be exceeded. This dynamic temperature management allows the use of smaller, less expensive resistor and contactor components compared to those required for passive continuous-duty designs
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 effectively reduces the risk of overheating and subsequent damage to pre-charge components, allowing them to be designed for lower requirements, resulting in cost savings and reduced vehicle downtime.
Implementation Method 1
The resistor of the pre-charge circuit limits the current flow to the high-voltage bus from the traction battery
Implementation Method 2
The predetermined number of times may be based on a magnitude or a duration of a peak magnitude of a current through the resistor during the preceding predetermined period of time
Data Source
AI summary
A vehicle is disclosed comprising a pre-charge circuit, including a resistor, that selectively connects a traction battery to an electrical impedance. A controller is programmed to inhibit pre-charging for an amount of time when a predetermined number of pre-charge cycles have occurred within a preceding predetermined period of time. The predetermined number of pre-charge cycles may be based on a voltage or current magnitude across the resistor during the previous pre-charge cycles. The predetermined number of times may be modified based on prior successful and failed pre-charge cycles. A method of limiting a temperature increase of a pre-charge resistor is disclosed comprising counting a number of prior pre-charge cycles and inhibiting pre-charging when the number of prior pre-charge cycles within the preceding period of time exceeds a threshold.