E-Axle Cable Resistance Monitoring for Connector Temperature Control
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Solution Overview
Problem
Current methods for determining cable and connector temperatures in electric drive systems with e-axle modules are imprecise, leading to potential overheating and reduced drive power, often requiring costly and space-intensive solutions like increasing copper cross-sections in connection cables.
Innovation Solution
A method involving measuring voltage differences between a DC voltage source and a power electronics system, determining reference sum resistance, and calculating average temperatures of connection cables and connectors, allowing for precise temperature assessment and reduced drive power by differentiating resistances and using temperature coefficients for the conduction material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the copper cross-section of connection cables is increased to reduce electrical resistance and temperature load, then temperature control is improved, but costs and space requirements increase
Solution Approach 1:
The patent changes the measurement parameters from direct temperature sensing to electrical resistance measurement. By measuring the voltage difference and calculating resistance (R = U/I), the system indirectly determines temperature through the known temperature-resistance relationship of copper, avoiding the need for physical temperature sensors and complex cooling systems.
Solution Approach 2:
The patent replaces direct thermal measurement mechanisms with electrical measurement mechanisms. Instead of using temperature sensors that require physical contact and complex signal processing, the system uses voltage and current measurements to calculate resistance, which then provides temperature information through material properties.
2Reliability
If complex cooling systems are implemented to protect temperature-sensitive components, then component protection is improved, but device complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the measured resistance value is continuously monitored and compared against threshold values. When the resistance indicates excessive temperature, the system can trigger protective actions such as reducing current or activating cooling, creating a closed-loop control system that protects components without requiring complex preventive cooling infrastructure.
Solution Approach 2:
The patent performs preliminary measurements to establish reference resistance values at known temperatures during system initialization or calibration phases. These reference values are stored and used for subsequent temperature calculations, allowing the system to prepare protection strategies in advance rather than reacting to thermal emergencies.
3Productivity
If temperature sensors are installed at electrical loads to determine derating thresholds, then power management is improved, but measurement precision is reduced
Solution Approach 1:
The patent makes the connection cable and connector perform a dual function: they conduct electrical current and simultaneously serve as the sensing element for temperature measurement. The inherent electrical resistance of these components, which would normally be a source of heat and measurement error, becomes the measurement signal itself, eliminating the need for separate sensors that introduce additional uncertainty.
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 significantly improves temperature precision, increases drive power, reduces costs by allowing for smaller cable cross-sections, and enhances safety by detecting increasing contact resistances and undesirable temperature increases.
Implementation Method 1
These are attached to the inverter with plug or screw connectors. The connection cables and the connections on the inverter of the power electronics system heat up at high currents.
Implementation Method 2
The connection cables and the connections on the inverter of the power electronics system heat up at high currents.
Implementation Method 3
measuring a voltage U_Batt at a DC voltage source and measuring a voltage U_INV at an input of the power electronics system... a difference U_delta between the voltage U_Batt of the DC voltage source and the voltage U_INV at an input of the power electronics system is measured and the sum resistance R_sum is determined
Data Source
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 voltage is measured at a DC voltage source (16) and a voltage U_INV is measured at an input of the 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 U_INV 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 a differentiation 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 at least one input of a power electronics system (18) of an e-axle module (32) of an electrically powered vehicle.