Electric Machine Thermal Model for Temperature Tracking After Shutdown
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Solution Overview
Problem
Existing methods for determining the temperature of electrical machines lose critical information when the inverter is switched off, leading to inaccurate temperature calculations upon restart, especially for motors with and without temperature sensors, affecting control quality and thermal protection.
Innovation Solution
A computing device is integrated with the supply unit to determine the electrical machine's temperature using a thermal model, even when the supply unit is not energized, ensuring continuous temperature calculation and access to precise temperature data upon restart, and allowing for real-time monitoring and validation of sensor temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the inverter is switched off to save energy, then energy consumption is reduced, but temperature information is lost leading to inaccurate temperature calculations upon restart
Solution Approach 1:
The system performs preliminary cooling calculations before the inverter is switched off. The computing device calculates the cooling curve and determines the temperature at the moment of shutdown, storing this information for later use. This preliminary action ensures that when the inverter restarts, the system already has accurate temperature information without needing to recalculate from scratch.
Solution Approach 2:
The computing device creates a copy of the thermal model and operates it independently from the inverter's control unit. This separate thermal model continues to run and calculate temperature even when the inverter is off, copying the necessary calculations and storing results. This allows the system to maintain temperature information without requiring the inverter to remain powered on.
2Measurement precision
If a temperature sensor is installed in the rotor winding to directly measure temperature, then temperature measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical/physical temperature sensor installation in the rotor winding with a computational thermal model. Instead of physically measuring temperature with a sensor that requires complex wiring to rotating parts, the system uses mathematical thermal models to calculate temperature based on operating parameters, power losses, and cooling conditions. This substitution eliminates the need for physical sensors in difficult-to-reach locations while maintaining measurement accuracy.
3Reliability
If conservative initial temperature values are used after shutdown, then reliability of temperature estimation is improved, but measurement precision deteriorates
Solution Approach 1:
The system uses feedback from the thermal model to continuously update temperature estimates. When the inverter is running, the thermal model receives real-time operating data and adjusts temperature calculations accordingly. Upon restart, the system uses the stored temperature information and continues the thermal model calculation with actual operating parameters, creating a feedback loop that progressively refines the temperature estimate rather than relying on static conservative values.
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 approach ensures accurate and precise temperature determination at any time, improving control quality and thermal protection by maintaining accurate temperature information and reducing the need for conservative initial values, while also enabling continuous monitoring and validation of sensor temperatures.
Implementation Method 1
The thermal path can include multiple thermal resistances and multiple thermal time constants
Implementation Method 2
If the motor is now energized, the motor windings heat up, and this heating can be calculated using the thermal model of the motor in the software
Data Source
AI summary
The invention relates to an arrangement for determining a temperature (T1, T2) of an electric machine (4), comprising a supply unit (2) for operating the machine (4) and a computing device (3) which can be associated with the supply unit (2), the supply unit (2) and the computing device (3) being configured to determine a temperature (T1, T2) of the electric machine (4) by means of a thermal model (TM1, TM2) of the electric machine (4), wherein the supply unit (2) and the computing device (3) cooperate such that the computing device (3) determines the temperature (T1, T2) of the electric machine (4) at least when there is no current on the supply unit (2).