Insulation Resistance Measurement Using AC Signal Coupling
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Solution Overview
Problem
Existing insulation resistance measuring methods for high-voltage batteries are complex, costly, and prone to external interference, with conventional methods either breaking the insulation during measurement or requiring complicated circuit designs.
Innovation Solution
A device and method using an operational amplifier connected to the negative electrode terminal of a high-voltage battery, incorporating a shunt resistance and control unit to measure insulation resistance without affecting the battery voltage, utilizing a switch and signal control to determine insulation resistance through voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC current is forced to flow by breaking insulation to measure leakage current, then leakage current measurement is achieved, but insulation is broken during measurement
Solution Approach 1:
The patent introduces a coupling condenser as an intermediary component between the high-voltage battery and the measurement circuit. The condenser allows AC measurement signals to pass while blocking DC leakage current, enabling indirect measurement of insulation resistance without directly breaking the insulation path. This mediator approach permits measurement while preserving insulation integrity.
Solution Approach 2:
The patent replaces the conventional DC current injection method with an AC signal-based measurement approach. By using AC signals and measuring the resulting voltage across the coupling condenser, the system achieves insulation resistance measurement without the need to physically break insulation or force DC current through the insulation path.
2Measurement precision
If coupling condenser is connected between battery terminals and vehicle with AC signal application, then insulation resistance component can be measured, but circuit designing becomes complicated with limitations
Solution Approach 1:
The patent extracts the measurement function from the main power circuit by using a separate, dedicated measurement path through the coupling condenser. The measurement circuit is designed as an independent module that only handles AC signals, separating it from the high-voltage DC power circuit. This extraction simplifies the overall circuit design by isolating the measurement functionality.
Solution Approach 2:
The coupling condenser serves multiple functions: it acts as an AC signal path for measurement, blocks DC leakage current, and provides galvanic isolation between the high-voltage battery and the measurement circuit. This multi-functionality reduces the need for additional components, thereby simplifying the circuit design while maintaining measurement precision.
3Measurement precision
If conventional insulation resistance measuring methods are used, then measurement can be performed, but external interference affects measurement accuracy
Solution Approach 1:
The patent creates an electrically isolated measurement environment by using the coupling condenser to block external interference and ground paths. The AC signal-based measurement method operates in an electrically 'inert' environment that is isolated from the high-voltage DC field and external electromagnetic interference, thereby improving measurement accuracy.
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 precise and cost-effective measurement of insulation resistance without breaking the insulation, reducing external interference and circuit complexity, allowing for accurate detection of leakage currents in high-voltage batteries.
Implementation Method 1
an operational amplifier connected to both terminals of the shunt resistance and configured to detect and output voltage between both ends of the shunt resistance
Data Source
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AI summary
The present disclosure relates to an insulation resistance measuring device and method, including a parameter resistance connected to a negative electrode terminal of a battery; a shunt resistance connectable to the parameter resistance; a current detection circuit including an operational amplifier configured to detect and output voltage between both ends of the shunt resistance; and a control unit configured to determine the insulation resistance of the battery using a switch control terminal configured to control a switch connected between the parameter resistance and the shunt resistance to an ON or OFF state, a detection signal output terminal configured to selectively apply a first high voltage signal and a first low voltage signal to the shunt resistance, a control signal output terminal configured to apply a control voltage signal to the operational amplifier to adjust an output voltage of the operational amplifier within a predetermined range, an ADC connected to an output terminal of the operational amplifier, and a predefined insulation resistance formula that includes, as a parameter, a first voltage change amount with respect to the output voltage of the operational amplifier being measured through the ADC when the first high voltage signal and the first low voltage signal are applied to the shunt resistance.