Electric Machine Coil Temperature Determination via Electrical Resistance
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Solution Overview
Problem
Existing methods for monitoring the temperature of electric machine coils, such as those in electric vehicles, are prone to inaccuracies due to the use of temperature sensors, which are costly and subject to measurement variances, potentially leading to overheating and damage.
Innovation Solution
A method that calculates the actual temperature of electric machine coils by detecting voltage and current strength in no-load and active short circuit states, using formulas to determine magnetic flux and coil resistance, allowing for temperature calculation without the need for temperature sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature sensors are used to detect the actual temperature of the electric machine, then the temperature monitoring function is achieved, but the costs increase and measurement inaccuracies occur
Solution Approach 1:
The patent replaces the physical temperature sensor (mechanical/thermal measurement system) with an electrical measurement system that determines temperature indirectly through resistance measurements and thermal models. The control device calculates temperature based on voltage and current measurements during specific operating states (no-load and active short circuit), eliminating the need for direct thermal contact sensors.
Solution Approach 2:
The patent introduces electrical resistance as an intermediary parameter to infer temperature. Instead of measuring temperature directly, the system measures coil resistance during specific operating states and uses thermal models to calculate temperature from these resistance values, making the temperature determination indirect but accurate.
2Object-affected harmful factors
If temperature sensors are used to monitor coil temperature, then overheating protection is provided, but measurement variances and inaccuracies reduce reliability
Solution Approach 1:
The patent implements a feedback mechanism where the control device continuously monitors electrical parameters (voltage, current, resistance) and adjusts its temperature calculations accordingly. By measuring resistance during specific operating states and comparing against thermal models, the system creates a closed-loop feedback system that compensates for measurement uncertainties and provides accurate temperature information for overheating protection.
Solution Approach 2:
The patent changes the measurement parameter from direct temperature measurement to electrical resistance measurement. By measuring resistance during no-load and active short circuit states and using the known temperature-coefficient of copper, the system transforms electrical measurements into accurate temperature information, improving measurement precision.
3Measurement precision
If the electric machine is switched into no-load and active short circuit states for measurement, then accurate temperature determination is achieved, but temporary loss of thrust occurs
Solution Approach 1:
The patent employs periodic measurements during specific operating states (no-load and active short circuit) rather than continuous measurement. These periodic measurements are performed at predetermined intervals or under specific conditions, allowing the system to maintain productivity during normal operation while obtaining accurate temperature data periodically for monitoring and protection.
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 provides accurate temperature determination of electric machine coils, reducing the risk of overheating and damage, and can be used in hybrid vehicles to compensate for temporary loss of thrust during temperature calculation, also providing a start value for temperature models in hot start scenarios.
Implementation Method 1
detecting a voltage in a no-load state of the electric machine; detecting a current strength in an induced short circuit state of the electric machine
Implementation Method 2
As a result of the current conducted through the coils, the coils heat up
Data Source
AI summary
A method for determining an actual temperature of a coil of an electric machine, includes detecting a voltage in a no-load state of the electric machine; detecting a current strength in an induced short circuit state of the electric machine; calculating an actual stator coil resistance as a function of the voltage detected during the no-load state and the current strength detected during the active short circuit” state; and calculating the actual temperature of the coil of the electric machine as a function of the actual stator coil resistance.