Infrared Rotor Temperature Measurement via Stator Aperture
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Solution Overview
Problem
Current methods for measuring electric motor rotor temperature during operation are inadequate, particularly for induction motors, as they do not allow for direct temperature measurement of the rotor surface and require power shutdown for estimation, limiting performance and motor life.
Innovation Solution
The solution involves creating a first aperture through the stator for direct alignment with an infrared sensor to measure rotor temperature, with a second aperture for stator temperature measurement, and using a step-aperture through stator laminations to enable non-contact infrared sensing in an air gap, allowing for simultaneous measurement of rotor and stator surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal resistance network-based temperature estimators are used, then temperature measurement can be performed during operation, but the rotor temperature cannot be directly measured due to inaccessibility
Solution Approach 1:
The patent divides the measurement task into two separate aperture systems: a first aperture for rotor temperature measurement and a second aperture for stator temperature measurement. This segmentation allows each aperture to be optimized for its specific measurement target, with the first aperture positioned to view the rotor surface through the air gap and the second aperture positioned to view the stator surface, thereby achieving direct rotor temperature measurement without requiring complex indirect estimation methods
Solution Approach 2:
The patent introduces an intermediary optical system including a semi-transparent mirror and beam splitter that allows the single sensor to view both the rotor surface through the first aperture and the stator surface through the second aperture. This intermediary optical path division enables simultaneous measurement of both surfaces without requiring direct physical access to the rotor, resolving the inaccessibility problem while maintaining measurement precision
2Measurement precision
If back-EMF method is used for permanent magnet motors, then rotor magnet temperature can be indirectly estimated, but power input must be stopped for a predetermined period of time
Solution Approach 1:
The patent replaces the electrical back-EMF measurement method with an optical infrared measurement system. Instead of using electrical signals and requiring power shutdown to measure back-EMF, the system uses an infrared sensor to directly detect thermal radiation from the rotor surface through the first aperture. This substitution allows continuous operation during measurement, eliminating the productivity loss while achieving temperature measurement precision
Solution Approach 2:
The patent utilizes infrared radiation detection, which relies on the thermal emission properties of materials at different temperatures. The infrared sensor detects the characteristic infrared signature emitted by the rotor surface, allowing temperature measurement during operation without requiring power shutdown. This approach replaces electrical measurement with optical detection, maintaining measurement accuracy while enabling continuous motor operation
3Adaptability or versatility
If induction motors are used, then permanent magnets are not present in the rotor, but suitable methods to measure rotor temperature are not available
Solution Approach 1:
The patent creates a universal measurement system that works for all motor types including both permanent magnet motors and induction motors. The first aperture positioned to view the rotor surface through the air gap provides direct optical access to the rotor regardless of whether it contains permanent magnets or not. The infrared sensor measures thermal radiation from the rotor surface itself rather than relying on magnet-specific back-EMF signals, making the system universally applicable to all motor configurations while maintaining measurement 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 provides accurate, non-contact rotor temperature measurement during operation, enhancing motor performance and longevity by avoiding thermal overprotection and enabling continuous monitoring without power interruption.
Implementation Method 1
A first aperture or opening extends through the stator. A sensor is positioned in alignment with the first aperture sensing a temperature of at least a surface of the rotor in a line-of-sight with the sensor
Implementation Method 2
an infrared sensor to enable non-contact infrared sensing in an air gap
Data Source
AI summary
An apparatus for automobile vehicle rotor temperature measurement includes a motor having a rotor. A stator has the rotor positioned within the stator. An aperture extends through the stator. A sensor is positioned in alignment with the aperture sensing a temperature of at least a surface of the rotor.