Sensorless Plunger Position Estimation in MV Switching Devices
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Solution Overview
Problem
Existing medium voltage switching devices with electromagnetic actuators face challenges in accurately determining the operating status and position of movable plungers without relying on expensive and cumbersome proximity sensors or micro-switches, which affects breaking capabilities and increases industrial costs.
Innovation Solution
A method that uses a test coil and control means to provide test signals to estimate the operating status of the electromagnetic actuator, including the position of the movable plunger, without dedicated position sensors, by analyzing the electrical behavior of the test coil and applying transformation functions based on observation data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If proximity sensors (magnetic sensors) are adopted to sense the position of the movable plunger, then measurement precision is improved, but device complexity and industrial costs increase due to cabling requirements
Solution Approach 1:
The patent extracts the sensing function from dedicated external sensors and relocates it to the control unit by utilizing measurement data already available from the excitation coil circuit. This eliminates the need for separate proximity sensors and their associated cabling, while maintaining position detection capability through mathematical estimation based on electrical characteristics.
Solution Approach 2:
The control unit is given a dual function: it both controls the switching device operation and performs position sensing by analyzing electrical measurements from the excitation coil. This multi-functionality eliminates the need for dedicated sensing components and reduces overall system complexity while maintaining measurement precision.
2Measurement precision
If micro-switches are adopted to sense the position of the movable plunger, then measurement precision is improved, but reliability worsens and industrial costs increase
Solution Approach 1:
The patent replaces the mechanical micro-switch sensing system with an electrical measurement system. Instead of using mechanical contacts that physically detect plunger position, the system uses electrical measurements from the excitation coil and mathematical transformations to estimate position, thereby eliminating mechanical wear and improving reliability.
Solution Approach 2:
The patent introduces an intermediary mathematical model that transforms electrical measurements (voltage, current, power factor) into position information. This intermediary transformation layer allows indirect but reliable position sensing without mechanical contact, improving reliability while maintaining measurement precision.
3Measurement precision
If dedicated position sensors are installed, then measurement precision is improved, but loss of substance increases due to additional components and materials
Solution Approach 1:
The patent merges the position sensing function with the existing control and excitation systems. By combining multiple measurement parameters (voltage, current, power factor) from the excitation coil into a unified position estimation process, the system achieves accurate operating status detection without requiring separate sensing components or additional materials.
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 allows for precise, sensorless estimation of the operating status and position of the movable plunger, reducing costs and size by eliminating the need for dedicated sensing arrangements, while identifying potential issues like short circuits in the excitation coil windings.
Implementation Method 1
A method is disclosed which makes it possible to provide advanced estimation data indicative of the operating status of an electromagnetic actuator (13) of a switching device (1), without the provision of dedicated sensing arrangements. To this end, a test voltage signal is applied across the terminals of a test coil (132, 134) of the electromagnetic actuator (13).
Implementation Method 2
The electromagnetic actuator comprises a magnetic core provided with an excitation coil operatively associated to a movable plunger mechanically coupled to the mobile contacts of the switching device. The magnetic field, which is induced by the excitation current circulating in the excitation coil, generates a force that operates the movable plunger.
Data Source
AI summary
A method for determining the operating status of a MV switching device is provided. The method includes providing a test signal to said test coil for an observation period of time. Measuring data is obtained which is indicative of the voltage at the terminals of the test coil and of the current circulating along the test coil during the observation period of time. Observation data is calculated which is indicative of the electric behavior of the test coil at the end of said observation period of time. A transformation function is selected which is indicative of the electromagnetic behavior of the electromagnetic actuator. First estimation data is calculated which is indicative of the operating status of the electromagnetic actuator.