Power Supply Relay Abnormality Diagnosis via Capacitor Voltage Monitoring
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Solution Overview
Problem
Conventional electric power source circuits face difficulties in diagnosing abnormalities in power supply relays, particularly fixed-closure and fixed-open states, which can lead to fusion abnormalities and are challenging to detect due to capacitor charging mechanisms.
Innovation Solution
An abnormality diagnosis system that includes a power supply relay, a capacitor, a pre-charge path, and a switch, where the diagnosis is based on the drop of the charge voltage of the capacitor after the switch and power supply relay are operated to open, and a motor relay is used to diagnose fixed-open abnormalities by monitoring charge voltage changes when all switches are closed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power supply relay is used to open and close the electric current path, then the electric power conversion circuit can be controlled, but it becomes difficult to diagnose whether the power supply relay is in a fixed-closure or fixed-open abnormality state
Solution Approach 1:
A diagnosis switch is introduced as an intermediary component between the battery and the capacitor. This switch enables the diagnosis circuit to control the charging of the capacitor independently, creating a test condition that reveals relay abnormalities. The diagnosis switch acts as a mediator that allows the diagnosis circuit to manipulate the circuit state for detection purposes without directly observing the relay's internal state.
Solution Approach 2:
The diagnosis circuit performs preliminary actions by controlling the diagnosis switch to charge the capacitor to a predetermined voltage before attempting to detect relay abnormalities. This preliminary charging action creates a known initial state that is essential for subsequent abnormality detection, allowing the system to establish baseline conditions for diagnosis.
2Object-affected harmful factors
If the capacitor is pre-charged by turning on the ignition switch, then the large current flowing to the capacitor is restricted, but the fixed-closure of the power supply relay becomes difficult to diagnose due to insufficient voltage difference
Solution Approach 1:
The diagnosis switch serves as a mediator that provides an alternative charging path for the capacitor, independent of the power supply relay. By controlling this intermediary switch, the diagnosis circuit can charge the capacitor to a predetermined voltage level, creating a controlled test condition that generates sufficient voltage difference for detecting fixed-closure abnormalities, regardless of the relay's state during normal operation.
Solution Approach 2:
The diagnosis circuit changes the voltage parameter of the capacitor by controlling the diagnosis switch to charge the capacitor to a predetermined voltage. This parameter change creates a distinct voltage difference that enables detection of fixed-closure abnormalities. The system manipulates the capacitor's charge state as a variable to facilitate abnormality detection.
3Reliability
If a power supply relay capable of supplying large electric current is used to avoid fusion abnormality, then fusion abnormality is prevented, but the relay becomes large in size and costly
Solution Approach 1:
The pre-charge circuit performs a preliminary action by charging the capacitor before the power supply relay closes. This preliminary charging reduces the voltage difference across the relay at the moment of closure, thereby limiting the inrush current that could cause fusion. By preparing the circuit in advance, the system prevents harmful effects without requiring an oversized relay.
Solution Approach 2:
The capacitor and pre-charge circuit act as intermediaries between the battery and the electric power conversion circuit. The capacitor absorbs the inrush current surge that would otherwise flow through the relay, protecting the relay from fusion. This intermediary energy storage element allows the use of a smaller, more cost-effective relay while maintaining reliability.
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
Effectively detects fixed-closure and fixed-open abnormalities in power supply relays, preventing fusion issues and improving diagnostic accuracy by monitoring capacitor voltage drops and changes, ensuring reliable operation and preventing damage.
Implementation Method 1
a capacitor (42) connected between a current path (5) formed between the power conversion circuit and the power supply relay (40) and a reference potential source
Implementation Method 2
a pre-charge path (55) formed between the power source and the capacitor (42) to pre-charge the capacitor (42) by the power source (12)
Data Source
AI summary
A control unit for a rotary electric machine includes a first current command module, a second current command module, a change module, and a return module. The first module performs a first current command on a maximum efficiency characteristic line on a d-q plane thereby to drive the machine at a maximum efficiency. The second module performs a second current command on a switching line set at a retard angle side relative to the maximum efficiency characteristic line. The change module changes a control mode from a rectangular wave voltage phase control mode to an overmodulation current control mode when an operation point of the machine reaches the switching line. The return module returns the current command from the second command to the first command after performance of the second command for a predetermined period.