Capacitor Degradation Monitoring via Resonance Frequency Shifts
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Solution Overview
Problem
In adjustable speed drives and power converters, it is challenging to evaluate the degradation level of capacitors in power filters without disconnecting them, as this can result in significant downtime and costs, especially in critical applications like petrochemical plants, where stopping drives is not permissible.
Innovation Solution
A method that injects controllable disturbances into capacitors to measure their resonance frequencies, allowing for the estimation of degradation levels without shutting down the system, using the power converter as a sensor to detect shifts in resonance frequencies indicative of capacitor health, and implementing software to calculate and monitor degradation levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the drive system is disconnected to perform health checks on capacitors, then measurement precision is improved, but productivity deteriorates due to shutdown and downtime costs
Solution Approach 1:
The patent enables continuous health monitoring of capacitors while the drive system remains operational. The controller continuously measures voltage and current signals during normal operation, calculates impedance values, and monitors capacitor degradation without requiring system shutdown, thus maintaining both measurement capability and system productivity
Solution Approach 2:
The controller uses the drive system's own operational voltage and current signals to assess capacitor health. By utilizing existing operational data and internal processing capabilities, the system performs self-diagnosis without external intervention or system disconnection, eliminating downtime while maintaining assessment accuracy
2Measurement precision
If multiple drives are disconnected for filter health checks, then measurement precision is improved, but loss of time increases due to considerable shutdown scale
Solution Approach 1:
The system performs continuous capacitor health monitoring during normal operation of multiple drives. The controller simultaneously monitors voltage and current signals from all connected drives, enabling parallel assessment of multiple filter capacitors without sequential shutdowns, thus eliminating time loss while maintaining detection precision
3Productivity
If the drive system is operated continuously without disconnection, then productivity is maintained, but reliability deteriorates due to inability to detect capacitor degradation
Solution Approach 1:
The controller continuously measures voltage and current signals, calculates impedance values, and compares them against reference values to detect capacitor degradation. This feedback mechanism provides real-time reliability information during continuous operation, enabling predictive maintenance while maintaining productivity, thus resolving the contradiction between operational continuity and failure detection capability
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 continuous monitoring of capacitor health, preventing equipment failures and unpredictable stops, improving safety, reliability, and reducing costs by allowing for predictive maintenance and minimizing harmonic stress, thus extending the lifetime of power filters.
Implementation Method 1
injecting a controllable disturbance and measuring the response of at least one of the capacitors, determining the non-degraded resonance frequency of the capacitor, injecting a second controllable disturbance and measuring the response of the capacitor, determining the degraded resonance frequency of the capacitor
Data Source
AI summary
The present invention is directed at a method for evaluating the degradation level of capacitors of a power filter connected to an adjustable speed drive (ASD) or a power converter. The invention is also directed at an adjustable speed drive and a power converter provided for performing the method.