Electric Motor Rotor Temperature Correction Using Torque and Slip
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Solution Overview
Problem
Existing methods for determining rotor temperature in electric machines are inefficient, particularly in applications like automobiles, where dynamic correction of initialization errors after a terminal status change is needed, and often require complex computations and sensor installations on moving parts.
Innovation Solution
A method that calculates a support value using a rotor temperature model and motor current, and an auxiliary value using motor torque and slip, then links these to correct the rotor temperature value, allowing for a simplified thermal model and dynamic error correction without the need for complex regulators or additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a temperature model is used to calculate rotor temperature, then sensor installation on moving parts is avoided, but initialization errors occur after terminal status change
Solution Approach 1:
The patent implements a feedback mechanism by calculating a correction value based on the difference between support values (from temperature model) and auxiliary values (from electrical measurements). This correction value is fed back to adjust the temperature model, continuously improving accuracy after terminal status changes without requiring physical sensors on moving parts.
Solution Approach 2:
The patent replaces the mechanical sensor installation on moving rotor parts with an electrical field-based measurement approach. By using electrical measurements (current, voltage, impedance) to infer temperature and calculating correction values, the system eliminates the need for physical contact sensors on rotating components while maintaining measurement capability.
2Measurement precision
If a complex regulator is used to correct temperature model errors, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent uses a simple, computationally inexpensive correction mechanism that can be rapidly recalculated after each terminal status change. The correction value is computed using basic arithmetic operations on electrical measurements and temperature model outputs, avoiding complex regulatory algorithms while achieving sufficient accuracy for the application.
3Measurement precision
If a multi-body thermal model is used to improve temperature accuracy, then measurement precision improves, but computing resources are excessively consumed
Solution Approach 1:
The patent changes the approach from using complex multi-body thermal models with many parameters to a simplified model that uses electrical measurements (current, voltage, impedance) as key parameters. The correction value calculation uses these electrical parameters directly, reducing computational complexity while maintaining accuracy through the feedback correction mechanism.
Data Source
AI summary
Disclosed is a method for determining a rotor temperature value TRot for an electric machine, such as an electric motor. In one example, the method includes calculating a support value Pcu2_Trot using a rotor temperature value Trot that is determined with a temperature model and a motor current value Isdq. An auxiliary value Pcu2_Ref can be determined using a motor torque Trq and a motor slip value ωslip. The support value Pcu2_Trot can be linked with the auxiliary value Pcu2_Ref in order to obtain a corrected rotor temperature value DeltaTrot. Furthermore, the temperature model can be modified using the corrected rotor temperature value DeltaTrot in order to obtain a corrected temperature model. Finally, the rotor temperature value TRot can be determined using the corrected temperature model.