Pockels Cell Voltage Measurement with Bias Control
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Solution Overview
Problem
Conventional methods for measuring high-voltage DC systems using voltage dividers and electro-optical crystals face challenges such as increased device size and accuracy degradation due to charge fluctuations, particularly in non-contact electric field sensors employing the Pockels effect.
Innovation Solution
A voltage measuring device incorporating a Pockels cell with a grounded conductor, crystal end face electrode, bias electrode, and intra-crystal electric field measurement unit, which maintains the internal electric field at zero to prevent charge fluctuations, utilizing a light source, polarizer, analyzer, and photodetector to accurately measure DC voltage without increasing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage divider including a plurality of resistors is used to measure DC voltage, then the DC voltage can be measured, but the device size increases due to the need to soak resistors in insulating oil
Solution Approach 1:
The patent replaces the conventional voltage divider using resistors and insulating oil with an electro-optical measurement system. A Pockels cell (electro-optical crystal) detects voltage through the Pockels effect, where an applied electric field changes the refractive index of the crystal, modulating light passing through it. This optical measurement method eliminates the need for large insulating oil tanks and resistor assemblies, significantly reducing device size while maintaining measurement capability.
Solution Approach 2:
The patent introduces light as an intermediary medium to transfer voltage information. The Pockels cell acts as a mediator that converts electrical voltage into optical signal changes through the Pockels effect. This intermediary approach allows non-contact voltage measurement and eliminates the need for direct electrical connection and large insulating structures.
2Volume of stationary object
If a non-contact electric field sensor using an electro-optical crystal is used to measure DC voltage, then the device size is reduced, but measurement accuracy decreases due to charge fluctuations through the electro-optical crystal
Solution Approach 1:
The patent implements a feedback mechanism using a feedback electrode connected to a high-impedance operational amplifier. The operational amplifier continuously monitors the charge accumulation on the floating electrode and applies a compensating voltage through the feedback electrode to counteract charge fluctuations. This feedback control stabilizes the electric field environment around the Pockels cell, maintaining measurement accuracy over time despite the non-contact measurement approach.
Solution Approach 2:
The floating electrode configuration with high-impedance connection creates a self-regulating system where charge fluctuations are naturally minimized. The high-impedance connection prevents significant charge flow, and the floating potential automatically adjusts to maintain electrostatic equilibrium, reducing charge accumulation effects without requiring active intervention.
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 effectively reduces the size of the voltage measuring device and minimizes accuracy loss due to charge fluctuations, providing precise DC voltage measurement.
Implementation Method 1
a method using the linear electro-optical effect called the Pockels effect has been proposed as a method for measuring voltage
Implementation Method 2
The linear electro-optical effect is a phenomenon in which when an electric field is applied to an electro-optical crystal, a refractive index changes linearly in proportion to the intensity of the electric field, causing birefringence
Implementation Method 3
analyzer to transmit the light reflected by the Pockels cell; a photodetector to detect the light emitted from the analyzer
Data Source
Figure 1~4
Figure 5~7
Figure 8~10
AI summary
The present invention provides a voltage measuring device capable of measuring the DC voltage of a high-voltage conductor by using a bias supply control unit that controls a bias electrode so as to keep voltage through the inside of an electro-optical crystal at zero. The voltage measuring device of the present invention includes: a light source (5); a polarizer (6) polarizing light emitted from the light source (5); a grounded conductor (2a) provided apart from a high-voltage conductor (1), the grounded conductor (2a) being grounded; a crystal end face electrode (4) having a floating potential, the crystal end face electrode (4) being out of contact with the grounded conductor (2a) and the high-voltage conductor (1); a Pockels cell (3) transmitting light emitted from the polarizer (6), the Pockels cell (3) being provided between the crystal end face electrode (4) and the grounded conductor (2a); an analyzer (7) transmitting light reflected by the Pockels cell (3); a photodetector (8) detecting light emitted from the analyzer (7); an intra-crystal electric field measurement unit (9) converting voltage output by the photodetector (8) into intra-crystal electric field and outputting the intra-crystal electric field; a bias electrode (10) provided between the high-voltage conductor (1) and the crystal end face electrode (4) in such a way as to be out of contact with the crystal end face electrode (4); a bias supply (11) connected to the bias electrode (10); a bias supply control unit (12) controlling the bias supply (11) to keep internal electric field of the Pockels cell (3) at zero, the bias supply control unit (12) being connected to the intra-crystal electric field measurement unit (9); and a measurement voltage calculation unit (13) obtaining voltage of the high-voltage conductor (1) based on results output by the intra-crystal electric field measurement unit (9) and the bias supply control unit (12).