Electric Motor Permanent Magnet Temperature Control
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Solution Overview
Problem
The performance of electric motors in vehicles is degraded due to irreversible demagnetization of permanent magnets, which occurs without accurate temperature measurement, as temperature sensors cannot be attached to the rotating magnets, leading to permanent performance loss.
Innovation Solution
A control method that includes a sensor to measure the temperature of the electric motor, a controller to calculate the temperature of the permanent magnet using a thermal equivalent circuit, and an inverter to adjust the power supply, reducing power when the temperature exceeds a predetermined level to prevent demagnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is attached to the permanent magnet to directly measure its temperature, then the temperature measurement accuracy is improved, but the device complexity increases and the sensor cannot be attached due to the rotating rotor structure
Solution Approach 1:
The patent introduces a thermal equivalent circuit as an intermediary model to indirectly determine the permanent magnet temperature. Instead of directly measuring the magnet temperature with a sensor, the system measures temperatures at accessible locations (stator, rotor housing) and uses the thermal equivalent circuit model to calculate the magnet temperature based on heat transfer relationships, thus avoiding the need to attach sensors to the rotating magnet.
Solution Approach 2:
The patent replaces the mechanical/physical sensor attachment approach with a thermal modeling and calculation approach. By substituting direct physical measurement with indirect thermal circuit analysis, the system achieves temperature measurement without the mechanical complexity of sensor mounting on rotating components.
2Device complexity
If the temperature of the permanent magnet is not accurately determined, then the device complexity is reduced, but irreversible demagnetization occurs leading to permanent performance degradation
Solution Approach 1:
The patent implements preliminary protective action by continuously monitoring the calculated permanent magnet temperature and comparing it against a predetermined threshold. When the temperature exceeds the threshold, the control system proactively reduces power supply to the electric motor before irreversible demagnetization can occur, thus preventing permanent performance degradation.
Solution Approach 2:
The patent establishes a feedback control loop where the calculated permanent magnet temperature is continuously fed back to the control system. Based on this feedback, the controller adjusts the power supply to the motor, reducing power when temperature exceeds thresholds, thereby maintaining magnet performance through closed-loop temperature management.
3Productivity
If power is continuously supplied to the electric motor to maintain productivity, then the productivity is improved, but the temperature of the permanent magnet increases causing performance degradation
Solution Approach 1:
The patent implements dynamic power management by continuously adjusting the power supply to the electric motor based on real-time permanent magnet temperature conditions. Rather than maintaining constant power output, the system dynamically modulates power levels - reducing power when temperature thresholds are exceeded and allowing higher power when temperatures are acceptable, thus balancing productivity with thermal management.
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
Effectively prevents performance degradation by accurately calculating the temperature of the permanent magnet and adjusting the power supply, thereby maintaining the motor's efficiency and extending its lifespan.
Implementation Method 1
calculating a temperature of the permanent magnet based on a previously calculated amount of heat generation corresponding to the torque
Implementation Method 2
The controller may correspond the electric motor to the thermal equivalent circuit including at least one electric component
Data Source
AI summary
A vehicle and method of controlling the same are provided in which the performance of an electric motor is prevented from being degraded by efficiently and more accurately calculating the temperature of a permanent magnet within the electric motor to adjust the amount of power supplied to the electric motor. The vehicle includes an electric motor having a stator, a rotor, and a permanent magnet and a sensor that measures the temperature of the electric motor. An inverter drives the electric motor and a controller generates a predetermined heat quantity by supplying power to the electric motor to calculate the temperature of the permanent magnet based on the temperature of the electric motor at a predetermined point measured using the sensor. When the temperature of the permanent magnet exceeds a predetermined temperature, the controller reduces the supply of the power.