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Maintenance of capacitors

Technical Support

For Safe Operation, Perform the Following Maintenance Inspections:

  • Abnormal Temperature Rise :
    If the temperature rise exceeds     15°C , and is not due to equipment failure, it may indicate operation outside the recommended temperature range ( -40°C to +45°C ). Investigate and correct the cause.

  • Rust or Corrosion :
    Apply anti-rust treatments, such as rust removal and protective coating.

  • Cracks or Bursting in the Enclosure :
    If any cracks or rupture are found,     replace the capacitor immediately .

  • Water Exposure :
    If exposed to rain or dripping water,     relocate the unit to a suitable installation site.

  • Loose Screws :
    Loosening may be caused by     vibration . Take anti-vibration measures or change the installation location.

  • Accumulation of Metal Dust or Debris :
    If dust accumulation is heavy,     relocate the equipment ; if minor, clean it using a brush or similar tool.

  • Swelling of the Enclosure :
    Bulging indicates that the     internal safety device has been activated . Investigate the cause of the failure and replace the capacitor .

Oil Leakage :
Check for openings in the enclosure. If leakage is found, replace the capacitor immediately .

Routine Visual Inspections:

Visually check for the following abnormalities:

  • Swelling or deformation of the enclosure

  • Unusual noise

  • Oil leakage or traces of leaks

  • Arcing or sparking

  • Fuse status

Signs of overheating at cable terminals (e.g., discolored insulation )

Periodic Maintenance During Power Shutdown:

Perform maintenance after power is disconnected for at least 5 minutes , and after the capacitor is fully discharged (short-circuited safely).

  1. Check the tightness and contact condition of all screw terminals (recommended one week after initial energization).

  2. Remove accumulated dust on capacitors and related components.

Inspect the condition of circuit breakers, protective devices, feeder cables, grounding wires , and ensure all connections are in good working order.

 Capacitor Capacity Measurement Method:

  • For both high-voltage and low-voltage three-phase (3φ) capacitor banks, specific procedures should be followed for accurate capacity measurement. (Detailed procedure can be appended based on specific equipment or standards.)

Ca=CU-V
Cb=CU-W
Cc=CV-W
Total Capacity (C)= 2/3(Ca+Cb+Cc) 


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