Electric Machine Temperature Sensing With Dual-Sensor Curve Selection
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Solution Overview
Problem
Existing temperature measurement methods using NTC thermistors face ambiguity in output values due to decreasing gradient with increasing temperature, making it difficult to accurately determine temperature changes, especially at higher temperatures, as multiple temperature values can be associated with a single output value.
Innovation Solution
A method and system that utilize two temperature sensors, where the second sensor determines the temperature range for the characteristic curve branches of the first sensor, allowing for the selection of a unique characteristic curve branch and thus eliminating ambiguity in temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single NTC thermistor is used for temperature measurement, then the device complexity is low, but the measurement precision deteriorates at higher temperatures due to decreasing gradient in the characteristic curve
Solution Approach 1:
The temperature measurement system is segmented into two functional parts: a second temperature sensor that provides coarse temperature range identification, and a first temperature sensor that provides precise temperature measurement within the identified range. This segmentation allows each sensor to operate in its optimal performance zone, resolving the contradiction between simple device structure and high measurement precision.
Solution Approach 2:
The second temperature sensor acts as an intermediary that determines the operating range for the first temperature sensor. By using the output signal from the second sensor to select the appropriate characteristic curve branch of the first sensor, the system ensures that the first sensor always operates in a range where its gradient is sufficient for accurate measurement, thus resolving the precision issue without complicating the overall system.
2Ease of operation
If the gradient of the characteristic curve decreases with increasing temperature, then the device operation is simpler, but the difficulty of detecting and measuring temperature changes increases
Solution Approach 1:
The system dynamically adapts the measurement approach based on the temperature range. The control device continuously monitors the output signal of the first temperature sensor and switches between different characteristic curve branches as temperature changes. This dynamic adaptation ensures that the system always uses the portion of the characteristic curve with sufficient gradient for accurate detection, maintaining ease of operation while solving the measurement difficulty.
Solution Approach 2:
The system changes the interpretation parameter (which characteristic curve branch is used) based on the temperature range identified by the second sensor. By switching between different branches of the characteristic curve with different gradients, the system maintains high sensitivity for temperature change detection across the entire temperature range while keeping the sensor operation simple.
3Measurement precision
If multiple characteristic curve branches are used to improve measurement accuracy across different temperature ranges, then the measurement precision improves, but the device complexity increases due to need for range selection
Solution Approach 1:
The temperature measurement function is segmented between two sensors: the second sensor handles the coarse segmentation of temperature ranges, while the first sensor provides fine-grained precision measurement within each range. This functional segmentation allows the use of multiple characteristic curve branches without proportionally increasing system complexity, as the range selection logic is handled by the simpler second sensor.
Solution Approach 2:
The second temperature sensor performs a preliminary determination of the temperature range before the precise measurement is made by the first sensor. This preliminary action of range identification simplifies the subsequent measurement process by pre-selecting the appropriate characteristic curve branch, thereby reducing the complexity of real-time decision-making while maintaining high measurement precision.
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
Enables accurate and unambiguous temperature determination in electric machines by using a second temperature sensor to select the correct temperature range and characteristic curve branch for the first sensor, improving measurement accuracy, particularly in initial temperature measurements where no previous profile is available.
Implementation Method 1
Thermistors, in particular NTC thermistors, are often used to measure temperature. The characteristic curve of these NTC thermistors, which indicates an output value, generally a voltage, as a function of the temperature
Data Source
AI summary
A temperature in an electric machine is determined based on temperature-dependent output values of a first temperature sensor and of a second temperature sensor. The first temperature sensor has a characteristic curve having a plurality of characteristic curve branches, wherein each characteristic curve branch is associated with a specific temperature range. The output value of the second temperature sensor is used to select a characteristic curve branch; the output value of the first temperature sensor is used to determine the temperature from the selected characteristic curve branch.