Coil Temperature Monitoring via Resistance-Based Thermal Modeling
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Solution Overview
Problem
Existing dynamoelectric machines face overheating issues due to the limitations of PTC sensors, which are not suitable for high temperature rise rates, leading to delayed switch-off signals and potential machine damage.
Innovation Solution
A method for monitoring winding temperature using a thermal model that determines heating power and generates warning or switch-off signals based on critical temperature values, without the need for temperature sensors, by calculating the winding temperature from relative resistance changes using the heating power evaluated during converter operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTC sensors are installed to protect windings against overheating, then thermal protection is provided, but the shutdown signal is delayed due to thermal inertia, resulting in overheating and potential machine failure
Solution Approach 1:
The patent replaces the mechanical/thermal sensor-based temperature detection system with an electrical measurement system. Instead of using PTC sensors that rely on thermal conduction and have inherent thermal inertia, the invention measures the actual winding temperature by detecting the electrical resistance of the winding, which changes predictably with temperature. This substitution of measurement principle eliminates the thermal inertia delay entirely, as electrical resistance changes occur instantaneously with temperature changes, providing immediate shutdown signals when critical temperatures are reached.
Solution Approach 2:
The patent creates an electrical copy or proxy measurement of the thermal state. Rather than directly measuring temperature with a thermal sensor, it measures the electrical resistance, which serves as a proxy indicator of winding temperature. The control unit uses the known temperature-resistance characteristics of the winding material to calculate the actual temperature from the measured resistance, providing an instantaneous thermal state copy without thermal delay.
2Reliability
If PTC sensors are used for temperature monitoring, then thermal protection is achieved, but the sensors are not suitable for high temperature rise rates of 20-30 K/s
Solution Approach 1:
The patent replaces the thermal sensor measurement mechanism with an electrical resistance measurement mechanism. PTC sensors cannot respond to temperature rise rates of 20-30 K/s due to their thermal mass and thermal conduction time constants. In contrast, electrical resistance measurements occur instantaneously, allowing the system to accurately track and respond to extremely high temperature rise rates without any response delay, making the protection system suitable for high-speed thermal transients.
3Object-affected harmful factors
If thermal sensors are installed in machine trains, then overheating protection is provided, but the sensors cause delayed response and potential damage to windings
Solution Approach 1:
The patent substitutes thermal contact sensors with non-contact electrical resistance measurement. The electrical resistance of the winding can be measured directly from the power supply side without any physical contact with the winding, eliminating the thermal inertia and response delay inherent in thermal sensors. This provides immediate detection of overheating conditions and instant shutdown capability, ensuring reliable winding protection against thermal damage.
4Extent of automation
If conventional thermal models are used, then temperature estimation is possible, but sensorless monitoring with high precision is difficult to achieve
Solution Approach 1:
The patent exploits the predictable parameter change of electrical resistance with temperature. The resistance of copper windings follows a well-defined linear relationship with temperature (R = R0[1 + α(T - T0)]), where α is the temperature coefficient. By measuring the resistance and applying this known physical relationship, the system achieves precise temperature determination without sensors. The control unit calculates temperature directly from the measured resistance using the known temperature-resistance characteristics, providing high-precision sensorless temperature monitoring.
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 sensorless monitoring of winding temperature, preventing overheating and machine failure, with improved thermal protection and efficient operation, especially suitable for high dynamic accelerations.
Implementation Method 1
a relative increase in a resistance of the winding, in particular of the copper winding or individual UVW motor strands, when the winding heats up, is determined from the heating power, in comparison to a standard reference value for 20°C winding temperature
Data Source
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AI summary
The invention relates to a method for monitoring a temperature of a coil of an electric machine (2) that is powered by a converter (1), wherein a heating power applied to the coil is ascertained, and the heating power is evaluated using a thermal model (104), and when a critical coil temperature value linked to the heating power is exceeded, a warning signal and/or a switch-off signal is generated.