Winding Temperature Estimation via High-Frequency Skin Effect
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Solution Overview
Problem
Existing methods for determining the winding temperature of an induction machine are imprecise, especially during dynamic processes, due to distortions from armature reactions and currents in damper circuits, and are difficult to apply for larger motor designs.
Innovation Solution
A device using the skin effect with high-frequency currents and a non-linear Kalman filter to estimate the winding temperature, incorporating a high-frequency model and a second Kalman filter for rotor position and speed estimation, to determine the winding temperature based on high-frequency resistance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors are installed in the winding to measure temperature directly, then measurement precision is improved, but device complexity increases and only local temperature can be measured
Solution Approach 1:
The patent replaces physical temperature sensors with an electrical measurement system. Instead of using mechanical/physical sensors that require installation in the winding, the invention uses resistance measurements combined with Kalman filtering algorithms to estimate temperature, thereby eliminating the need for complex sensor installation while achieving accurate temperature measurement
2Device complexity
If resistance measurement is used to determine winding temperature, then device complexity is reduced, but measurement precision deteriorates during dynamic processes due to armature reactions and damper circuit currents
Solution Approach 1:
The patent implements a feedback mechanism through the Kalman filter algorithm. The algorithm continuously compares the measured resistance values with the expected values from the thermal model, and uses the difference (innovation) to update and refine the temperature estimate, thereby compensating for disturbances from armature reactions and damper currents
Solution Approach 2:
The patent changes the parameter being measured from direct resistance to temperature estimation through mathematical transformation. By using the Kalman filter to process resistance measurements along with motor operating parameters, the system transforms the distorted resistance signal into an accurate temperature estimate, effectively separating the temperature signal from the noise caused by dynamic effects
3Measurement precision
If Kalman filter with fundamental oscillation model is used to determine winding temperature, then temperature estimation is achieved, but manufacturing precision and applicability deteriorate for larger motor designs
Solution Approach 1:
The patent creates a universal temperature estimation method that works across different motor sizes and operating conditions. The improved thermal model and Kalman filter configuration are designed to be scale-independent, making the system applicable to both small and large induction motors without requiring redesign, thereby achieving multi-functionality across different motor classes
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 provides an accurate and precise method for determining winding temperature in induction machines, even during dynamic processes, by leveraging the correlation between high-frequency resistance and temperature, and improves evaluation accuracy with thin iron coatings.
Implementation Method 1
a rotary field control for vector control of the rotary field machine with at least one id current controller, which is designed to provide a phase voltage for the winding and to impress a high-frequency voltage signal on the phase voltage in order to generate a winding current with a high-frequency superimposed current component for the winding receive
Data Source
Figure 1
AI summary
The present invention relates to a device (10) for determining the temperature TW of a winding of a rotating field machine comprising a stator and a rotor, comprising at least a first Kalman filter (K1) for calculating the temperature and a rotating field control for vector control of the rotating field machine with at least one id current controller, which is configured to impose a high-frequency voltage signal (HF) on the winding voltage in order to obtain a winding current with a high-frequency superimposed current component for the winding, which is supplied to the Kalman filter (K1), wherein the Kalman filter (K1) has a high-frequency model of the motor in order to determine the high-frequency resistance of the winding and from this, in turn, the winding temperature TW by means of a calculation function.