Tapered Pockels Crystal Surface Potential Measurement
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Solution Overview
Problem
Conventional surface potential measurement techniques fail to accurately measure the surface potential of electric-field-reduction systems in inverter-driven rotating electric machines due to high-frequency components in inverter pulse voltage and the risk of damage to tapered Pockels crystals used for measurement.
Innovation Solution
A surface-potential distribution measuring device employing a tapered Pockels crystal with a protection unit and a photodetector capable of following high-frequency components, which suppresses out-of-plane vibrations and prevents damage by maintaining a safe distance from the measurement target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a surface electrometer with a metallic probe is used to measure surface potential, then the measurement can be performed with simple equipment, but the high-frequency components of inverter pulse voltage cannot be followed and measurement accuracy is lost
Solution Approach 1:
The patent replaces the conventional metallic probe-based surface electrometer with a non-contact optical measurement system. A laser beam is directed at the measurement point on the electric-field-reduction system, and the reflected light is analyzed to determine surface potential. This substitution eliminates the mechanical contact and associated high-frequency response limitations, enabling accurate measurement of inverter pulse voltage with its high-frequency components.
2Measurement precision
If a metallic probe is placed close to the electric-field-reduction system for measurement, then the measurement can be performed, but static electricity and corona discharge occur causing measurement disturbance
Solution Approach 1:
The patent introduces light as an intermediary medium between the measurement system and the electric-field-reduction system. Instead of direct electrical contact or close proximity of metallic probes, the laser beam serves as a non-contact intermediary that interacts with the measurement point through optical reflection. This eliminates the generation of static electricity and corona discharge while still enabling surface potential measurement.
3Stability of the object's composition
If a tapered Pockels crystal is used to suppress out-of-plane vibration, then vibration suppression is achieved, but the structural strength decreases making the crystal vulnerable to damage
Solution Approach 1:
The patent applies a protective coating on the surface of the tapered Pockels crystal before it is subjected to measurement conditions. This protective layer acts as a cushion that prevents direct contact and potential damage to the crystal structure, especially at the vulnerable tapered regions. The coating maintains the vibration suppression benefits of the tapered shape while compensating for the reduced structural strength.
4Measurement precision
If the Pockels crystal is moved closer to the measurement target for accurate measurement, then measurement accuracy improves, but the risk of crystal damage increases
Solution Approach 1:
The patent uses a protective coating as an intermediary layer between the Pockels crystal and the measurement target (electric-field-reduction system). This coating allows the crystal to be positioned close to the measurement target for accurate measurement while preventing direct contact that could cause damage. The coating maintains the necessary gap for optical measurement while providing mechanical protection.
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
Enables accurate measurement of surface potential in electric-field-reduction systems with inverter pulse voltage without damaging the Pockels crystal, ensuring reliable data collection and maintaining the structural integrity of the measurement equipment.
Implementation Method 1
a Pockels crystal (11) to measure a change in light intensity caused by a change in refractive index, which changes according to surface potential
Implementation Method 2
a photodetector (16) to follow high-frequency components
Data Source
Figure 1
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Figure 3
AI summary
A surface-potential distribution measuring device (1) has: a laser light source (13); a Pockels crystal (11); a mirror; a photodetector (16) that detects light intensity of the laser beam reflected by the mirror; a holding and mounting part that holds and moves the Pockels crystal (11); a voltage correction database; and a calculation unit that identifies an input voltage corresponding to a testing output voltage as a surface potential of the electric-field-reduction system (3). The Pockels crystal (11) is formed in such a way that a size of a cross section of the Pockels crystal (11) that is perpendicular to an axial direction changes along the axial direction. The holding and mounting part (30) has a protection unit (31) to protect a structure of the Pockels crystal, a movement unit to (35) that moves the Pockels crystal in order to measure a surface potential of the electric-field-reduction system, and a drive control unit (37) to control the movement unit (35), (36).