Polyphase Motor Temperature Estimation During Stop
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Solution Overview
Problem
Existing motor temperature estimating devices inaccurately estimate coil temperatures in polyphase motors during stop conditions due to unequal currents in phase coils, leading to potential underestimation of actual temperatures.
Innovation Solution
A motor temperature estimating device that includes phase current sensors, a determination section to assess motor rotation, and separate temperature estimation sections for rotation and stop conditions, using transformed output signals to accurately estimate temperatures by considering individual phase currents during both states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the motor is stopped, then the currents in the phase coils are used for temperature estimation, but the currents in the respective phase coils are not equal leading to inaccurate temperature estimation
Solution Approach 1:
The temperature estimation process is segmented into two distinct paths: one for rotation conditions using transformed two-phase currents, and another for stop conditions using original three-phase currents. This segmentation allows each path to be optimized for its specific operating condition, resolving the contradiction between measurement precision and adaptability.
Solution Approach 2:
The system dynamically switches between different temperature estimation methods based on the motor's operating state. A determination section identifies whether the motor is rotating or stopped, and accordingly selects the appropriate estimation path. This dynamic adaptation enables accurate temperature estimation across both rotation and stop conditions.
2Device complexity
If transformation from three-phase currents to two-phase currents is performed, then the calculation is simplified, but the temperature estimation becomes inaccurate during stop condition
Solution Approach 1:
Different calculation methods are applied to different operating conditions. During rotation, the simplified two-phase transformation is used. During stop, the original three-phase current data is used directly without transformation. This local optimization of calculation quality for each operating condition resolves the contradiction between simplicity and accuracy.
3Device complexity
If a single temperature estimation method is used for both rotation and stop, then the device complexity is reduced, but the temperature estimation accuracy deteriorates during stop
Solution Approach 1:
The temperature estimation device achieves multi-functionality by incorporating two estimation paths within a single system. The first estimation section handles rotation conditions, while the second estimation section handles stop conditions. Both functions coexist in one device, maintaining relatively simple overall structure while achieving high accuracy across different operating states.
Data Source
AI summary
In a motor temperature estimating device including: a polyphase motor 1 having a first phase coil, a second phase coil and a third phase coil; current sensors; a determination section that determines whether or not the polyphase motor is rotating; and a transformation section that transforms a first phase output signal from the first phase current sensor, a second phase output signal from the second phase current sensor, and a third phase output signal from the third phase current sensor to output a post-transformation output signal, the post-transformation output signal is inputted to a first temperature estimation section that estimates the temperature of the polyphase motor during rotation, and the first phase output signal, the second phase output signal and the third phase output signal are inputted to a second temperature estimation section that estimates the temperature of the polyphase motor during stop.