Sensorless Permanent Magnet Temperature Estimation in Electric Motors
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Solution Overview
Problem
In electric motors, particularly permanent magnet machines, it is impractical to directly measure the temperature of permanent magnets located on the rotor, which affects motor performance and can lead to demagnetization and physical damage if not monitored effectively.
Innovation Solution
A sensorless PM temperature detection technique using known electrical parameters, such as back-electromotive force (back-emf), estimates the rotor temperature, which is indicative of the PM temperature, allowing for real-time prediction and updating of motor control parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct temperature sensors are installed on the rotor to measure PM temperature, then measurement precision is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent uses back-EMF as an intermediary parameter to indirectly measure PM temperature. Instead of directly measuring temperature with sensors on the rotor, the system measures electrical parameters (back-EMF) that correlate with temperature, thereby avoiding the complexity of direct temperature sensing while achieving accurate temperature estimation
Solution Approach 2:
The patent replaces mechanical/physical temperature sensors with an electrical measurement approach. By substituting direct thermal measurement with electrical parameter measurement (back-EMF), the system eliminates the need for physical sensor installation on the rotating rotor, reducing device complexity while maintaining measurement capability
2Reliability
If no temperature monitoring is implemented, then device complexity is reduced, but reliability deteriorates due to risk of demagnetization and physical damage
Solution Approach 1:
The system uses its own operational electrical parameters (back-EMF) to monitor its own temperature state. The motor's electrical characteristics serve as the monitoring mechanism, eliminating the need for separate dedicated temperature monitoring hardware while ensuring reliability through continuous temperature awareness
Solution Approach 2:
The patent implements a feedback mechanism where back-EMF measurements continuously provide temperature information to the control system. This feedback loop enables real-time monitoring and protection against demagnetization by allowing the controller to adjust operating parameters based on estimated PM temperature
3Device complexity
If sensorless temperature detection is used, then device complexity is reduced, but measurement precision may deteriorate compared to direct sensing
Solution Approach 1:
The patent changes the measurement parameter from direct temperature to electrical parameter (back-EMF). By measuring electrical characteristics that vary with temperature and applying appropriate transformations/compensations, the system achieves accurate temperature estimation without direct thermal sensing, balancing simplicity and precision
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 method improves electric motor control accuracy, enables detection of critical states, and prevents damage by accurately determining the PM temperature without the need for direct temperature sensors, enhancing overall motor performance and reliability.
Implementation Method 1
A sensorless PM temperature detection technique using known electrical parameters, such as back-electromotive force (back-emf), estimates the rotor temperature
Data Source
AI summary
Techniques and apparatus for determining the temperature of a permanent magnet on a rotor of an electrical motor. An example techniques involves determining a first set of parameters for controlling the electrical motor. A temperature of the rotor during a runtime of the electrical motor is determined, based at least in part on the first set of parameters and a first back-electromotive force (back-emf) associated with the electrical motor. A first estimate of a magnetic flux of the permanent magnet is determined based on the temperature of the rotor. An operation of the electrical motor is controlled based at least in part on the first estimate of the magnetic flux of the permanent magnet.