R-Pro › Field cases › Air conditioning
PFC Circuit Electrolytic Capacitor Swelling (Increased Ripple Current → Capacitance Drop)
Likely causes
DC link electrolytic capacitor reaching end of life (typically 8–10 years) → rising ESR → swelling
Check: Visual check: top cross vent bulging or electrolyte residue. Measure capacitance with LCR — replace if below 80% of rated (e.g., 450V 1000μF → below 800μF). Measure ESR: normal below 100mΩ, above 500mΩ indicates active degradation.
What to do: Replace with same voltage and capacitance, upgraded to ≥105°C. Also inspect PFC inductor core for saturation (concurrent damage is common). After replacement, verify DC link voltage waveform on oscilloscope: ripple ≤±15V is normal.
Ambient temperature above 55°C + frequent ON/OFF cycles → premature capacitor degradation
Check: Measure outdoor unit internal temperature with IR thermometer — above 55°C indicates poor heat rejection. Check shading and ventilation around outdoor unit. Review control log for daily startup count.
What to do: Install shading over outdoor unit and ensure clearance (minimum 300mm from front). Excessive ON/OFF: adjust temperature setpoints to reduce cycles. In life-shortening environments, preventive replacement every 5 years is recommended.
After capacitor replacement, always verify discharge: confirm DC link voltage is below 50V at least 5 minutes after power off before touching. Never work with wet hands.
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