Electric Machine Winding Temperature Monitoring Without PTC Delay
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing dynamoelectric machines face overheating issues due to the limitations of PTC sensors, which are not suitable for high temperature increase rates, leading to delayed switch-off signals and potential damage to the winding.
Innovation Solution
A method for monitoring the winding temperature of electric machines using a thermal model to evaluate heating power, generating warning and switch-off signals when critical values are exceeded, allowing for sensorless temperature monitoring during ongoing converter operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTC sensors are installed to protect the winding from overheating, then thermal protection is provided, but the response is delayed due to thermal inertia causing overheating damage
Solution Approach 1:
The patent replaces the mechanical/thermal sensor-based protection system with an electrical measurement system. Instead of using PTC sensors that rely on thermal conduction and have inherent thermal inertia, the invention measures winding temperature indirectly through electrical resistance measurements, which respond instantaneously to temperature changes without thermal delay.
Solution Approach 2:
The patent introduces electrical resistance as an intermediary parameter to measure winding temperature. Rather than directly measuring temperature with thermal sensors, the system measures resistance (which changes with temperature) and calculates temperature from this intermediate measurement, thereby avoiding the thermal inertia problem of direct temperature sensing.
2Measurement precision
If resistance measurement is performed to determine winding temperature, then accurate temperature monitoring is achieved, but separate measurement sequences with DC currents are required causing interference and operation interruption
Solution Approach 1:
The patent makes the measurement system multi-functional by using the existing AC operating currents for both motor operation and temperature measurement. The same current paths and measurement circuits used for normal motor control are also utilized for resistance-based temperature monitoring, eliminating the need for separate measurement sequences and DC current sources.
Solution Approach 2:
The patent enables continuous temperature monitoring during normal motor operation without interruption. By measuring resistance using the ongoing AC operating currents, the system maintains continuous measurement capability rather than requiring periodic interruptions with separate DC measurement sequences.
3Reliability
If thermal sensors are used for temperature monitoring, then overheating protection is provided, but sensorless monitoring during ongoing operation is not achieved
Solution Approach 1:
The patent enables the motor winding to monitor its own temperature through its inherent electrical properties. The winding's resistance, which naturally changes with temperature, serves as the sensing element, eliminating the need for external thermal sensors. The motor's own operating currents are used for measurement, making the system self-sufficient.
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
Prevents overheating and machine failure by accurately monitoring winding temperature in real-time, reducing the need for thermal sensors and improving thermal motor protection, especially in high dynamic acceleration applications.
Implementation Method 1
The method is advantageously based on a determination of a relative increase in a resistance of the winding, in particular of the copper winding (or individual UVW motor strands), when this winding heats up (cf. basic laws of physics of the temperature dependence of the electrical resistance)
Implementation Method 2
not the electrical resistance, but the heating power, is determined directly (linearly proportional to the resistance acc. Pcu=I2R)
Data Source
AI summary
In a method for monitoring a winding temperature of a winding of an electric machine powered by a converter, a heating power applied to the winding of the electric machine is determined and evaluated using a thermal model. A relative increase in a resistance of the winding, when the winding heats up, is determined from the heating power in comparison with a standard reference value for 20° C. winding temperature. The winding temperature is calculated from the relative increase in the resistance, and a warning signal and/or a switch-off signal is generated when a critical winding temperature value is exceeded.