Electric Motor Thermal Management via Back-EMF Model
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Solution Overview
Problem
Existing electric motor thermal management systems rely on electromechanical thermal switches, which are expensive, unreliable, and lack verification mechanisms for proper operation, posing risks due to overheating and overload conditions.
Innovation Solution
A thermal model-based system that estimates motor temperatures using differential equations and Laplace transforms, eliminating the need for electromechanical thermal switches by monitoring electrical parameters to prevent overheating and detect overload conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electromechanical thermal switch is used to protect the electric motor, then the motor can be protected against overheating, but the system becomes expensive and less reliable
Solution Approach 1:
The patent replaces the electromechanical thermal switch with an electronic thermal model-based monitoring system. The system uses a processor to calculate motor temperature based on electrical parameters (current, voltage, time) and thermal characteristics, eliminating the need for mechanical thermal switches and their associated reliability issues.
Solution Approach 2:
The patent creates a virtual thermal model that copies the thermal behavior of the motor without requiring physical thermal sensors or switches. The thermal model mathematically replicates temperature evolution based on electrical inputs and thermal parameters, providing a software-based alternative to hardware thermal protection.
2Reliability
If an electromechanical thermal switch is used, then motor protection is provided, but the cost increases
Solution Approach 1:
The electromechanical thermal switch is replaced with an electronic calculation-based system using a processor and thermal model. This substitution eliminates the need for expensive specialized thermal protection hardware, reducing overall system cost while maintaining protection functionality.
Solution Approach 2:
The system uses the motor's own electrical parameters (current, voltage, time) to calculate its thermal state, eliminating the need for external thermal sensors or switches. The motor essentially monitors itself through its operational electrical characteristics.
3Reliability
If an electromechanical thermal switch is used, then thermal protection is provided, but there is no mechanism for verifying proper operation
Solution Approach 1:
The thermal model continuously calculates motor temperature based on real-time electrical parameters and provides feedback to the control system. This enables ongoing verification of thermal protection status and allows the system to detect when protection is needed, something electromechanical switches cannot do.
Solution Approach 2:
The processor acts as an intermediary between the motor's electrical parameters and the thermal protection function. It calculates temperature evolution and provides detailed thermal state information, enabling verification and monitoring that is impossible with direct electromechanical switching.
4Productivity
If the motor operates at high power, then productivity increases, but the risk of overheating increases
Solution Approach 1:
The thermal model calculates temperature evolution in advance based on planned or current electrical parameters, allowing the system to predict overheating risks before they occur. This enables preventive action to be taken, such as reducing power or activating cooling, before dangerous temperatures are reached.
Solution Approach 2:
The system dynamically adjusts motor operation based on real-time thermal model calculations. As the motor operates, the thermal model continuously updates temperature estimates, and the control system can dynamically modify power delivery to maintain safe operating temperatures while maximizing productivity.
Data Source
AI summary
A method and apparatus for electric motor thermal management is provided. A thermal model allows estimation of temperatures of an electric motor and determination of a motor overload condition. The thermal model is based on electrical parameters that can be measured in a motor control circuit. An electric motor control method and circuit utilizes a back electromotive force (EMF) measurement circuit, a processor coupled to the back EMF measurement circuit for receiving a back EMF measurement and for calculating a thermal model of the electric motor, the thermal model based on a stator-to-ambient thermal resistance value accounting for a sum of a stator-to-case thermal resistance and a case-to-ambient thermal resistance, and an electric motor driver circuit coupled to the processor for providing drive signals for controlling delivery of power to the electric motor based on the thermal model of the electric motor.