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Precautions for maintenance and inspection
(2) Smoothing capacitors
A large-capacity aluminum electrolytic capacitor is used for smoothing in the main
circuit DC section, and an aluminum electrolytic capacitor is used for stabilizing the
control power in the control circuit. Their characteristics are deteriorated by the
adverse effects of ripple currents, etc. The replacement intervals greatly vary with the
ambient temperature and operating conditions. When the inverter is operated in air-
conditioned, normal environment conditions, replace the capacitors about every 10
years.
When a certain period of time has elapsed, the capacitors will deteriorate more rapidly.
Check the capacitors at least every year (less than six months if the life will be expired
soon).
The appearance criteria for inspection are as follows:
1) Case: Check the side and bottom faces for expansion
2) Sealing plate: Check for remarkable warp and extreme crack.
3) Check for external crack, discoloration, fluid leakage, etc. Judge that the capacitor
has reached its life when the measured capacitance of the capacitor reduced below
85% of the rating.
(3) Relays
To prevent a contact fault, etc., relays must be replaced according to the cumulative
number of switching times (switching life).