MITSUBISHI ELECTRIC FR-S520 - Manual (Page 165)

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(2) Smoothing capacitors
A large-capacity aluminum electrolytic capacitor is used for smoothing the DC in the
main circuit, and an aluminum electrolytic capacitor is also used for stabilizing the
control power in the control circuit.
Their characteristics are adversely affected by ripple current, etc. When the inverter is
operated in an ordinary, air-conditioned environment, change the capacitors about
every 5 years. When 5 years have 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). Check the following:
1) Case (side faces and bottom face for expansion)
2) Sealing plate (for remarkable warp and extreme crack)
3) Appearance, external cracks, discoloration, leakage.
When the measured capacitance of the capacitor has reduced below 85% of the
rating, change the capacitor.
(3) Relays
To prevent a contact fault, etc., relays must be changed according to the number of
accumulative switching times (switching life).