E-Axle Cable Resistance Monitoring for Connector Temperature Derating
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Solution Overview
Problem
Current methods for determining the temperature of connecting cables and plugs in electric drive systems, particularly in e-axis modules, are inefficient and costly, leading to potential overheating and reduced drive power due to high electrical resistance, which necessitates derating and increased cooling efforts.
Innovation Solution
A method involving voltage measurements at a DC voltage source and power electronics, adjusting measurement accuracy, determining reference sum resistance, and calculating the temperature of connecting cables and elements, allowing for precise temperature determination and reduced drive power output by differentiating resistances and monitoring temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the copper cross-section of connecting cables is increased to reduce temperature load, then the electrical resistance decreases and heating is reduced, but the cost increases and additional space is required
Solution Approach 1:
The patent changes the parameter being monitored from direct temperature measurement to electrical resistance measurement. By measuring resistance changes in the connecting cable, the system can infer temperature changes without requiring larger cable cross-sections or additional cooling infrastructure.
Solution Approach 2:
The patent replaces physical/thermal measurement systems (temperature sensors, cooling systems) with an electrical measurement system. Resistance measurement provides temperature information through electrical properties rather than mechanical thermal sensing.
2Temperature
If complex cooling systems are implemented for inverter inputs, then temperature-sensitive components are protected, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical cooling systems with simple electrical resistance measurements. By monitoring resistance changes that correlate with temperature, the system protects temperature-sensitive components without requiring physical cooling infrastructure.
Solution Approach 2:
The connecting cable itself serves as the sensing element. The cable's electrical resistance naturally changes with temperature, providing self-monitoring capability without requiring separate sensors or active cooling systems.
3Reliability
If drive power is reduced before temperature thresholds are exceeded (derating), then component safety is maintained, but productivity decreases
Solution Approach 1:
The patent implements continuous feedback monitoring of cable temperature through resistance measurements. This real-time information allows the control system to optimize power delivery by preventing derating until actual temperature thresholds are approached, rather than using conservative pre-limits.
Solution Approach 2:
The patent enables dynamic adjustment of drive power based on actual cable temperature conditions. Rather than static derating, the system continuously adapts power levels to match real-time thermal states, maximizing productivity while maintaining safety.
4Measurement precision
If temperature sensors are installed at electrical loads, then temperature monitoring is achieved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing connecting cable serve dual purposes: power transmission and temperature sensing. The cable's inherent electrical resistance provides temperature information without requiring separate sensor installations at electrical loads.
Solution Approach 2:
The connecting cable performs multiple functions simultaneously: it conducts electrical power and acts as a temperature sensor. This multi-functionality eliminates the need for separate temperature sensing components while maintaining measurement capability.
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 method enables more precise temperature determination, increasing drive power output and reducing costs by allowing for smaller cable cross sections and improved safety through early detection of increasing contact resistance.
Implementation Method 1
At high currents, the connecting cables and the connections on the power electronics inverter heat up... determination of a reference sum resistance Rsum ref of the connecting cable at a known temperature T ref... a difference Udelta between the voltages UBatt of the DC voltage source and UINV at an input of the power electronics is measured and the total resistance Rsum is determined... Determination of the temperature from repeated determination of the total resistance during operation
Implementation Method 2
At high currents, the connecting cables and the connections on the power electronics inverter heat up... the electrical resistance and thus the resulting heating
Data Source
Figure 1~2
Figure 3~4
Figure 5.1~5.2
AI summary
The invention relates to a method for ascertaining a cable temperature and/or connector temperature on an electric drive having an e-axle module (32) with an electric machine (30), a power electronics system (18) and a DC voltage source (16), in particular a high-voltage battery (10), which are connected together via a connection cable (36), at least the following method steps being carried out: A voltage U_Batt is measured at a DC voltage source (16) and a voltage U_INV is measured at an input of a power electronics system (18). Measurement accuracy is subsequently compared by referencing U_INV to U_Batt. This is followed by determining a reference sum resistance R_sum_ref of the connection cable (36) at a known temperature Tref. Then, with current flowing between the DC voltage source (16) and the power electronics system (18), a difference U_delta between the voltage U_Batt of the DC voltage source (16) and the voltage UJNV at an input of the power electronics system (18) is measured and the sum resistance R_sum is determined. Then, the temperature is determined from repeated determination of the sum resistance R_Sum during operation and the temperature of the connection cable (36), the connections and connecting elements, such as plugs, is calculated. This is followed by differentiating between the resistances R1 of a connection (12, 14) of the DC voltage source (16) and/or a resistance R2 of a connection cable (36) and/or a resistance R3 of an input of the power electronics system (18). Subsequently, a drive power of the electric drive is reduced, while the temperature of the connections (12, 14), the connection cable (36) and the at least one input of the power electronics system (18) exceeds a temperature threshold. The invention further relates to the use of the method to ascertain the temperature of a connection cable (36) for connection terminals (12, 14) of a DC voltage source (16) and the temperature of at least one input of a power electronics system (18) of an e-axle module (32) of an electrically powered vehicle.