Insulation Detector Using Segmented Capacitance for Fast Measurement
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Solution Overview
Problem
Conventional insulation detectors face challenges in accurately measuring high insulation resistance values, such as 100 megaohms, due to the long time constants associated with large capacitance values, and are hindered by the presence of discharge resistance, which complicates the measurement process.
Innovation Solution
The proposed insulation detector incorporates an intra-insulation detector capacitor with a voltage detecting unit and a current-path forming switch to measure the insulation resistance by analyzing the time constant of voltage changes across the capacitor, using a capacitance value negligible compared to the intra-apparatus capacitor, and includes a rectifier circuit and measurement resistor to detect insulation resistance between a load and ground or housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large capacitance value is used to measure high insulation resistance, then measurement precision is improved, but measurement time becomes excessively long
Solution Approach 1:
The patent divides the capacitance into two separate components: a large intra-apparatus capacitor (C0) that is always connected to the load, and a small intra-insulation detector capacitor (Cm) that is only connected during measurement. This segmentation allows the system to benefit from both large total capacitance for accuracy and small measurement capacitance for fast response time.
Solution Approach 2:
The patent makes the capacitance configuration dynamic by using a switch to connect or disconnect the intra-insulation detector capacitor (Cm) based on measurement needs. During normal operation, only the large intra-apparatus capacitor (C0) is connected; during measurement, the small capacitor (Cm) is added to the circuit. This dynamic adjustment optimizes both measurement speed and accuracy.
2Reliability
If discharge resistance is provided to discharge the capacitor, then safety is improved, but measurement accuracy deteriorates due to interference with the measurement process
Solution Approach 1:
The patent separates the discharge function from the measurement function by providing a dedicated discharge path through the discharge switch and discharge resistor that is independent from the measurement circuit. This allows the capacitor to be safely discharged when not in use without interfering with the insulation resistance measurement process.
Solution Approach 2:
The discharge switch is opened before measurement begins, ensuring the capacitor is fully charged and isolated from the discharge path. This preliminary action prevents discharge resistance from interfering with the measurement while maintaining safety through the separate discharge path that can be activated when needed.
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 configuration allows for highly accurate and simple detection of insulation resistance, reducing measurement time and overcoming the limitations of discharge resistance, enabling effective preventive maintenance by monitoring slight changes in insulation resistance.
Implementation Method 1
measuring, with the voltage detecting unit, a time constant of a change in the voltage of the intra-insulation detector capacitor
Implementation Method 2
a capacitance value of the intra-insulation detector capacitor is a value negligible in the measurement of the insulation resistance compared with a capacitance value of the intra-apparatus capacitor
Data Source
AI summary
An insulation detector for highly accurately detecting or measuring, with a simple configuration, insulation resistance of a load or an apparatus to a ground or a housing and connected to an electric apparatus including one or both of an intra-apparatus capacitor and a battery, the insulation detector including an intra-insulation detector capacitor, a voltage detecting unit that detects a voltage of the intra-insulation detector capacitor, and a current-path forming switch for connecting the ground or the housing, the intra-apparatus capacitor, and the intra-insulation detector capacitor in series and forming a current path including insulation resistance of the electric apparatus. The insulation detector measures the insulation resistance by measuring a time constant of a change in the voltage of the intra-insulation detector capacitor. A capacitance value of the intra-insulation detector capacitor is a value negligible in the measurement of the insulation resistance compared with a capacitance value of the intra-apparatus capacitor.