Synchronous Machine Flux Calibration via Thermal Equalization
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Solution Overview
Problem
Existing methods for calibrating the magnetic flux in synchronous machines are prone to errors due to temperature uncertainties, especially in high ambient temperatures, leading to suboptimal power utilization and safety concerns, as they rely on stator temperature estimates and require cooling before calibration can occur.
Innovation Solution
A method where the magnetic flux calibration for a synchronous machine is performed only after a predetermined shutdown period, allowing for temperature equalization between the stator and rotor, enabling calibration independent of ambient temperature, and using a flag system to track calibration status for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the magnetic flux is calibrated using stator temperature estimates, then the calibration can be performed continuously during operation, but the temperature measurement precision deteriorates due to the temperature difference between stator and rotor
Solution Approach 1:
The patent applies preliminary action by performing magnetic flux calibration during a predetermined shutdown period before operation begins. This ensures that the calibration is done when the rotor and stator temperatures are equalized, eliminating temperature measurement errors. The calibration results are then stored and used during subsequent operation, avoiding the need for continuous temperature-based calibration while maintaining high precision.
2Reliability
If the phase current is limited to maintain a safety distance from maximum permissible magnet temperature, then the magnet temperature is kept safe, but the power output of the synchronous machine is reduced
Solution Approach 1:
The patent replaces the conventional stator temperature estimation method with direct rotor temperature measurement using a temperature sensor mounted on the rotor. This substitution provides accurate real-time rotor temperature data, enabling precise phase current limitation control that maintains magnet safety while maximizing power output by avoiding unnecessary current restrictions.
3Measurement precision
If a temperature sensor is installed on the rotor to directly measure magnet temperature, then the temperature measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent implements multi-functionality by integrating the temperature sensor into the existing rotor structure, allowing it to serve both as a structural component and a temperature measurement device. The sensor is positioned to directly contact the permanent magnets, enabling accurate temperature measurement while utilizing the existing rotor assembly, thus minimizing additional complexity.
4Measurement precision
If the magnetic flux calibration is performed only after a predetermined shutdown period, then the temperature equalization between stator and rotor is achieved improving calibration accuracy, but the calibration frequency is reduced
Solution Approach 1:
The patent performs magnetic flux calibration in advance during shutdown periods when temperature equalization has occurred. The calibration results are stored in memory and reused during operation, eliminating the need for frequent recalibration. This preliminary calibration approach ensures high accuracy while maintaining continuous operational productivity.
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 allows for reliable and efficient operation of synchronous machines over a wide power range, including high temperatures, by ensuring accurate rotor temperature determination and magnetic flux calibration, thus optimizing torque control and extending the machine's operational capabilities.
Implementation Method 1
it is assumed that temperatures within the synchronous machine have been able to equalize due to the long period of time since the synchronous machine was switched off
Data Source
Figure 1~2
AI summary
The invention relates to a method and a device for controlling a synchronous machine which has a stator, a rotor and magnets disposed on the rotor. When the synchronous machine (S1) has been produced or serviced, a nominal value ψnenn is first set (S2) for the magnetic flux prevailing in the synchronous machine and a control system is flagged to indicate that no calibration has been carried out yet (S3). Tests are then performed repeatedly in order to check whether the synchronous machine has not been operated for at least a predetermined period of time (S4). If it has not, it is assumed that there is temperature balance between the stator and the rotor, such that the temperature to be measured at the stator is the same as the rotor temperature and can thus be used as a basis for calibration of the magnetic flux ψkalib (S5). The control system is then flagged, to indicate that the flux has been calibrated (S6). Normal operation can then continue (S7), checks being carried out continually to see whether the flux has already been calibrated (S8).