Mitsubishi Electric FR-D720 K Series Instruction Manual page 287

(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 surrounding air temperature and
operating conditions. When the inverter is operated in air-conditioned and 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, liquid leakage, etc. Judge that the capacitor has reached its life when the
measured capacitance of the capacitor reduced below 80% of the rating.
POINT
Refer to page 230 to perform the life check of the main circuit capacitor.
(3) Relay output terminals
 To prevent a contact fault, etc., relays must be replaced according to the cumulative number of switching times (switching
life).
 The control terminal block must be replaced in case of failure of either relay connected to the relay output terminals A, B,
and C. (After replacing the control terminal block, connect the jumper connector to the correct position in accordance with
the control logic of input signals. (Refer to page 22.))
Inspection items
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