Motor Temperature Estimation Using Segmented Thermal Gradients
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Solution Overview
Problem
Conventional motor controllers face challenges in accurately estimating motor temperature after shutdown, particularly due to the lack of consideration for ambient temperature changes, leading to reduced accuracy and increased processing load, which can result in the need for expensive microcomputers.
Innovation Solution
A motor controller with an estimated temperature calculating section that uses first and second temperature gradients to update the estimated temperature, reducing processing load while maintaining high accuracy, by storing and calculating temperature gradients for different temperature ranges and ambient conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a first-order approximate equation is used to calculate the estimated temperature of a stopped motor, then the processing load of the control section is reduced, but the accuracy of the estimated temperature is degraded
Solution Approach 1:
The temperature estimation process is segmented into two distinct phases: a first temporary estimation phase using a simplified first-order approximate equation, and a second refinement phase using a more accurate thermal reaction characteristic equation. This segmentation allows the system to use computationally efficient methods initially, then apply more accurate but computationally intensive calculations only when necessary (when the motor is stopped and time permits), thereby resolving the contradiction between processing speed and accuracy.
Solution Approach 2:
The control section performs a preliminary temperature estimation using the first-order approximate equation while the motor is still running or刚 stopped, obtaining a preliminary estimated temperature value. This preliminary action provides a quick estimate that can be used immediately for control decisions, while the more accurate calculation is performed subsequently when the motor is fully stopped, thus achieving both speed and accuracy requirements at different time points.
2Reliability
If protection elements such as bimetal or PTC are built in the motor housing, then the motor is protected from burning, but the size of the motor is enlarged
Solution Approach 1:
The invention replaces physical protection elements (mechanical/bimetallic devices) with an electronic control system that calculates estimated motor temperature based on electrical parameters (current, voltage, time) and thermal characteristics. This substitution eliminates the need for physical protection elements like bimetal strips or PTC devices, thereby maintaining motor protection functionality while avoiding the size increase that would result from incorporating these additional components.
Solution Approach 2:
The control section acts as an intermediary between the motor's electrical operation and thermal protection requirements. Instead of directly incorporating protection elements into the motor housing, the control section mediates by calculating temperature estimates from electrical parameters and controlling power delivery accordingly, thus providing protection without adding physical bulk to the motor structure.
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
The solution enables accurate motor temperature estimation with reduced processing load, allowing for precise protection against overheating without the need for large protection elements, thus enhancing motor control efficiency and reducing device size.
Implementation Method 1
When a motor abnormally generates heat, an electric circuit is interrupted by this protection element and the passage of electric current through the motor is stopped
Data Source
AI summary
A motor controller includes: an estimated temperature calculating section that calculates and stores an estimated temperature of a motor, and a control section that can perform a drive control of the motor only when this estimated temperature is not larger than a predetermined value. When the motor is stopped, a second temperature gradient while the temperature of the motor decreases from a stop-time temperature to a predetermined first set temperature is stored in correspondence to the stop-time temperature. The first temperature gradient corresponding to the estimated temperature at a time when the motor is stopped is calculated by using the first temperature gradient storing means, if the estimated temperature stored in the estimated temperature storing means when the motor is stopped is larger than the first set temperature. The estimated temperature stored in the estimated temperature storing means is updated according to a lapse of a stopping time of the motor by using the first temperature gradient calculated by the first temperature gradient calculating means.