Optical Temperature Sensor Head for EMI-Free Motor Winding Sensing
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Solution Overview
Problem
Conventional temperature sensors used in vehicles and electrical machines are prone to failure due to thermal expansion, require large construction, and are affected by electromagnetic interference, making them unsuitable for precise temperature measurement in harsh environments with limited space and strong magnetic fields.
Innovation Solution
An optical temperature sensor head using a polymer optical fiber (POF) with a sensor material, such as ruby crystals, is integrated directly onto the winding wire of an electric machine, providing an optical connection and a protective overmold to prevent heat dissipation and environmental interference, allowing for precise temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional temperature sensors with electrical measuring elements are used, then temperature measurement is possible, but the sensor construction becomes large and requires electromagnetic shielding
Solution Approach 1:
The patent replaces electrical measuring elements with an optical measurement system. A luminescent material is excited by light from an LED, and the luminescence intensity or decay time is measured optically. This substitution eliminates the need for electrical connections and electromagnetic shielding, significantly reducing sensor complexity while maintaining temperature measurement capability
Solution Approach 2:
The patent introduces an optical fiber as an intermediary to transmit light to and from the luminescent material. This allows the measuring system to be separated from the sensor head, enabling compact sensor construction without requiring complex electrical connections at the measurement point
2Measurement precision
If conventional temperature sensors with multiple components are used, then temperature measurement is possible, but the sensor is prone to failure due to thermal expansion differences
Solution Approach 1:
The patent replaces the electrical measuring element and its supporting structure with a purely optical system. The luminescent material's optical properties change with temperature, allowing measurement without mechanical connections that would be subject to thermal expansion stresses. This significantly improves reliability in applications with temperature cycling
Solution Approach 2:
The patent uses a luminescent material (such as a phosphor or ruby crystal) that combines the functions of temperature sensing and optical interaction. This composite approach eliminates the need for multiple separate components with different thermal expansion coefficients, thereby improving reliability
3Measurement precision
If conventional temperature sensors are used in locations with strong magnetic fields, then temperature measurement is possible, but electromagnetic shielding is required to prevent measurement errors
Solution Approach 1:
The patent replaces electrical signal transmission with optical signal transmission. Since optical fibers and luminescent materials are immune to electromagnetic interference, the sensor can be used in strong magnetic fields without requiring electromagnetic shielding, thus reducing device complexity while maintaining measurement accuracy
4Measurement precision
If conventional temperature sensors with electrical connections are used, then temperature measurement is possible, but the sensor requires large contact surfaces
Solution Approach 1:
The patent replaces electrical connections with optical coupling. The optical fiber can be coupled to the luminescent material with a very small contact area, eliminating the need for large contact surfaces required by electrical connections. This enables temperature measurement in locations with limited space
Solution Approach 2:
The patent uses an optical fiber with a flexible protective coating that can be brought into close proximity with the luminescent material. This flexible optical connection requires minimal contact area compared to rigid electrical connections, reducing the required contact surface diameter
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 offers a compact, mechanically stable, and interference-resistant temperature measurement system that accurately measures temperatures within electric machines, even in harsh conditions, with multiple sensors possible using a single light source and detector.
Implementation Method 1
optical temperature sensor head (101), in particular the sensor material (102) which is brought into thermal contact with the object whose temperature is to be measured and emits luminescence radiation when excited by light from a light-emitting diode
Implementation Method 2
the intensity of the emitted luminescence radiation is measured in two different wavelength ranges, and then the temperature of the sensor material emitting the luminescence radiation
Implementation Method 3
optically connected to a free end of an optical fiber
Implementation Method 4
A protective overmold prevents heat dissipation from the sensor material
Implementation Method 5
sensor material (102) which is brought into thermal contact with the object whose temperature is to be measured
Data Source
Figure 1A~1B
Figure 2A~2D
Figure 2E~2G
AI summary
An optical temperature sensor head is proposed, comprising an optical fiber and a sensor material optically connected to the free end of the optical fiber. The free end of the optical fiber is overmolded with a plastic material that overlaps the fiber and forms a protective body. A transparent window is arranged within this protective body, allowing optical communication with the free end of the optical fiber. Luminescence from the sensor material can penetrate the optical fiber. The protective body ensures that the temperature sensor head is mechanically stable and insensitive to environmental influences. Furthermore, a temperature sensor device incorporating such a temperature sensor head is proposed. Finally, an electrical machine is proposed, featuring a winding with a winding wire connected to the proposed temperature sensor head.