Ground Fault Detection Y-Capacitor Equilibrium Restoration
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Solution Overview
Problem
The accuracy of insulation resistance calculation in ground fault detection devices is reduced due to the influence of Y-capacitors, leading to increased detection time and costs, especially when stray capacitances are high, as the equilibrium state of Y-capacitors is disrupted during measurements.
Innovation Solution
A ground fault detection device with a detection capacitor and a switch group that temporarily switches between charging paths to rapidly restore the equilibrium state of Y-capacitors by forcing electric charge discharge in opposite directions, allowing for accurate insulation resistance calculation without additional hardware or increased detection time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If V0 measurement is performed immediately after Vein or Vc1p measurement, then detection time is reduced, but insulation resistance calculation accuracy deteriorates due to Y-capacitor imbalance
Solution Approach 1:
The control device performs a preliminary action by temporarily switching to the third charging path (Vc1p charging path) before the intended V0 measurement to restore the equilibrium state of the Y-capacitors. This preliminary restoration action ensures that when the V0 measurement is subsequently performed, the Y-capacitors are in a balanced state, thereby maintaining measurement accuracy while minimizing detection time.
Solution Approach 2:
The control device applies preliminary anti-action by temporarily switching to the third charging path (Vc1p charging path) after the second charging path (Vein charging path) measurement to counteract the imbalance caused by the Vein measurement. This anti-action restores the equilibrium state of the Y-capacitors before the next V0 measurement, preventing accuracy degradation without extending the overall detection time.
2Measurement precision
If additional equilibrium restoration circuitry is added, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The control device utilizes the existing switch group and charging paths for multiple purposes: normal Vein/Vc1p measurements, V0 measurements, and Y-capacitor equilibrium restoration. By making the switch group multi-functional, the system achieves accurate insulation resistance measurement without requiring additional dedicated restoration circuitry, thereby avoiding increased device complexity and cost.
Solution Approach 2:
The system performs self-service by using its own existing resources (switch group and charging paths) to restore the equilibrium state of the Y-capacitors. The control device temporarily switches to the third charging path to recharge the Y-capacitors when imbalance is detected, eliminating the need for external or additional restoration equipment.
3Productivity
If Y-capacitor capacitance is increased to improve vehicle performance, then vehicle performance is enhanced, but insulation resistance measurement accuracy deteriorates due to slower equilibrium recovery
Solution Approach 1:
The control device performs preliminary action by temporarily switching to the third charging path (Vc1p charging path) before the intended V0 measurement to proactively restore the equilibrium state of the Y-capacitors. This ensures that even with large capacitance values, the Y-capacitors are recharged and balanced before measurement, maintaining accuracy despite the slower natural recovery rate of larger capacitors.
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 approach prevents a reduction in insulation resistance detection accuracy due to Y-capacitor influence without extending detection time or increasing costs, as the Y-capacitors are rapidly returned to equilibrium through software-controlled switching, ensuring precise measurements.
Implementation Method 1
a detection capacitor configured to function as a flying capacitor
Implementation Method 2
a capacitor referred to as a Y-capacitor (line bypass capacitor) is often connected between a ground and positive and negative power supply lines
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
A ground fault detection device (100) includes: a detection capacitor (C1); a switch group (S1-S4) for switching between a first charging path connecting the battery (300) and the detection capacitor, a second charging path connecting the battery, a negative side insulation resistance (RLn) and the detection capacitor, a third charging path connecting the battery, a positive side insulation resistance (RLp) and the detection capacitor, and a measurement path for measuring a charging voltage of the detection capacitor; and a controller (110) configured to calculate the insulation resistance based on a charging voltage measured value of the detection capacitor which exists after charging each of the charging paths, wherein after measurement of the charging voltage of the second charging path, the controller is configured to cause the switch group to switch to the third charging path before switching to the first charging path.