Here is the English translation of your technical document titled "Technical Analysis of Voltage Fluctuations Caused by Capacitor Failures", keeping the professional tone and structured clarity appropriate for engineering documentation:

Technical Analysis of Voltage Fluctuations Caused by Capacitor Failures

The impact of capacitor anomalies on system voltage must be assessed based on the specific fault type and circuit characteristics. This document provides a systematic explanation from an engineering practice perspective.

I. Capacitor Function and Voltage Correlation Mechanism

1. Power Supply Filtering Applications

In rectifier output circuits, electrolytic capacitors smooth pulsating DC by charging and discharging. When capacitance degrades (e.g., 1000μF drops to 300μF), oscilloscope measurements show ripple voltage rising from 50mVp-p to 200mVp-p, though a multimeter may still show a stable average voltage. In extreme open-circuit cases, the rectifier may revert to half-wave operation, causing the output voltage to drop by 30–40%.

2. Power Compensation Applications

Field data from a 10kV distribution system in a chemical plant showed that when 30% of the parallel capacitor bank failed, the power factor dropped from 0.95 to 0.82, and bus voltage decreased from 10.2kV to 9.8kV (approximately a 4% drop). This is due to uncompensated reactive power from inductive loads, resulting in increased line current and voltage drops.

II. Voltage Signatures of Typical Fault Modes

III. Fault Diagnosis Workflow

1. System-Level Diagnostics

Record three-phase voltage imbalance (>2% indicates anomaly)

Monitor dynamic power factor (fluctuations >0.1 suggest compensation failure)

Analyze total harmonic distortion (capacitor failure may trigger resonance)

2. Component-Level Diagnostics

Use an LCR meter at 1kHz to check capacitance deviation (±15% threshold)

Perform dielectric withstand test at 1.5× rated voltage (replace if leakage >5mA)

Measure ESR (equivalent series resistance); ESR > 3× nominal in high-frequency circuits indicates failure

IV. Interference Factor Elimination Guidelines

1. Power Supply Quality Verification

Measure voltage fluctuation on power grid (stabilization needed if over ±10%)

Check transformer winding DC resistance (deviation >2% indicates inter-turn short)

2. Line Status Confirmation

Measure circuit contact resistance (>50mΩ suggests loose connections)

Evaluate cable current capacity (temperature rise >40K indicates overload)

V. Case Study

Issue: A semiconductor plant's vacuum coating equipment frequently reported undervoltage alarms.

Symptoms: DC bus voltage fluctuated between 600V and 550V

Investigation:
 1. Abnormal temperature detected in capacitor bank (peaked at 85°C)
 2. Visual inspection revealed bulging in 3 capacitor modules
 3. Capacitance measured at only 60% of rated value

Resolution: Replaced capacitors and added forced air cooling; voltage stabilized

VI. Technical Conclusion

The causal relationship between capacitor failures and voltage fluctuations is scenario-specific:

Direct correlation: Compensation capacitor failure leads to voltage drop (notable when inductive loads exceed 60%)

Indirect correlation: Filter capacitor open-circuit may reconfigure rectifier topology (e.g., full-wave to half-wave conversion)

Misdiagnosis risk: Line issues like poor contact may mimic similar voltage symptoms

Recommendation: Establish a three-tier diagnostic protocol-system parameter monitoring → device status evaluation → component-level testing-to ensure accurate fault localization.

If you need this formatted into a technical report or presentation format (e.g., Word or PowerPoint), let me know-I'd be happy to help.