Onboard Power Circuit Isolation for AC Inlet Ground Potential
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Solution Overview
Problem
Onboard power devices experience a potential difference between the AC inlet and body ground when the switching relay connects the bidirectional charging circuit and AC outlet, leading to potential safety and operational issues during AC power supply.
Innovation Solution
The onboard power device includes a voltage sensor with an input terminal isolated from the portion between the switching relay and the power storage device, preventing the AC inlet's potential from becoming equipotential with the power storage device's negative electrode bus bar, thus suppressing potential differences between the AC inlet and body ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the input terminal of the voltage sensor is electrically connected to the negative electrode bus bar between the switching relay and the power storage device, then the voltage sensor can measure the voltage accurately, but a potential difference is generated between the third power line and the body ground when AC power is supplied to the AC outlet
Solution Approach 1:
A ground line is introduced as an intermediary connection between the negative electrode bus bar and the body ground. This ground line serves as a mediator that allows the voltage sensor to reference the negative electrode bus bar potential while providing a controlled path to body ground, thereby preventing dangerous potential differences from developing between the third power line and body ground during AC power supply operations
2Adaptability or versatility
If the switching relay connects the second power line to the fourth power line for AC power supply to the AC outlet, then AC power can be supplied to external devices, but the potential of the third power line becomes approximately equal to the potential of the negative electrode bus bar, generating a potential difference with the body ground
Solution Approach 1:
The ground line acts as an intermediary that connects the negative electrode bus bar to the body ground, providing a controlled reference path. This allows the system to switch between different power line connections (second to third, second to fourth) without creating dangerous potential differences with the body ground, as the ground line establishes a stable reference potential
Data Source
AI summary
A onboard power device includes a power storage device, a bidirectional charging circuit connected to the power storage device via a first power line and connected to a second power line, an AC inlet configured to be connectable to an external power source and connected to a third power line, an AC outlet installed in a cabin and connected to a fourth power line, a switching relay configured to selectively connect the second power line to the third power line or the second power line to the fourth power line, and a voltage sensor including an input terminal connected to the third power line and an output terminal connected to a controller. The input terminal is electrically isolated from the portion between the switching relay and the power storage device.