Electric Compressor Ripple Diagnosis for Fault Source Isolation
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Solution Overview
Problem
Existing control systems for electric compressors in vehicle air conditioners face challenges in identifying and isolating the source of excessive ripple voltage, which can cause resonance and excessive current, especially when a vehicle-side load is connected, as they cannot distinguish between ripple voltage originating from the electric compressor and external equipment.
Innovation Solution
A control device with a detection unit to monitor ripple voltage, a determination unit to assess its abnormality, and a cause determination unit to differentiate between the electric compressor and external equipment as the source of the ripple voltage, using rotation speed control to diagnose and record the source of the abnormality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor is stopped to protect from excessive current due to ripple voltage, then equipment protection is improved, but the ability to operate the air conditioner is worsened
Solution Approach 1:
The control device acts as an intermediary that introduces a diagnostic phase between ripple voltage detection and motor stopping. By controlling the motor to rotate at a first rotation speed and then a second rotation speed while monitoring ripple voltage changes, the system identifies whether the compressor or external equipment is the source before taking protective action, thus avoiding unnecessary stops and maintaining productivity while ensuring reliability when needed.
2Object-affected harmful factors
If the electric compressor is stopped to prevent resonance from ripple voltage, then harmful effects are reduced, but the source of the problem cannot be isolated
Solution Approach 1:
The control device performs preliminary diagnostic actions by controlling the motor to rotate at different rotation speeds and monitoring ripple voltage changes before the actual protective stopping occurs. This preliminary action identifies whether the compressor or external equipment is the ripple voltage source, preserving information about the problem source while still preventing harmful resonance effects.
3Measurement precision
If the motor rotation speed is changed to diagnose ripple voltage source, then source identification is improved, but system complexity increases
Solution Approach 1:
The control device uses dynamic rotation speed changes as a diagnostic tool. By controlling the motor to rotate at a first rotation speed and then a second rotation speed while monitoring ripple voltage changes, the system dynamically adapts the motor operation to identify the ripple voltage source. This dynamic approach improves measurement precision while keeping the control logic relatively simple by reusing existing motor control capabilities.
Data Source
AI summary
Provided is a method for determining the generation source of ripple voltage when abnormal ripple voltage is detected. The control device is for an electric compressor, the control device comprising: a detection unit that detects ripple voltage; a judgment unit that judges whether the ripple voltage is abnormal based on the value of the ripple voltage; and a cause determination unit that determines whether the cause of the abnormality is the electric compressor or some other external device, based on the control result of the electric compressor.