7.4 List of Periodic Replacement Parts
7-9
MAINTENANCE AND INSPECTION
The service life of the DC link bus capacitor can be judged by “(1) Measurement of discharging time of the DC
link bus capacitor” or “(2) ON-time counting of DC link bus capacitor.”
(1) Measurement of discharging time of the DC link bus capacitor
• The discharging time of the DC link bus capacitor depends largely on the inverter’s internal load conditions, e.g.,
options attached or ON/OFF of digital I/O signals. If different from the initial value load conditions subject to
comparison (excl. terminal [EN1], [EN2]), it will not be possible to obtain measurement accuracy, and therefore
measurement is not be performed.
• When connecting a converter, or when connecting a DC common to another inverter, measurement is not
performed.
• The capacitance measuring conditions at the time of shipping are drastically restricted, e.g., all input terminals
being OFF in order to stabilize the load and measure the capacitance accurately. Those conditions are,
therefore, different from the actual operating conditions in almost all cases. If conditions are the same as the
factory default conditions (excl. terminal [EN1], [EN2]), the discharge time is automatically measured when the
power is turned OFF. However, the time will not be automatically measured if the conditions are different. In
such a case, return the conditions to the factory default values, and turn OFF the inverter. Measurement is
performed automatically (see capacitance measurement procedure below.)
Refer to “[1] Measuring the capacitance of DC link bus capacitor in comparison with initial value at time of
shipment”.
• To measure the capacitance of the DC link bus capacitor under ordinary operating conditions when the power is
turned OFF, it is necessary to set up the load conditions for ordinary operation and measure the reference
capacitance (initial setting) when the inverter is introduced. Refer to (2) on the following page for details on the
procedure used to set the capacitor capacitance (default value). Performing the setup procedure automatically
detects and saves the measuring conditions of the DC link bus capacitor.
Refer to “[2] Measuring the capacitance of the DC link bus capacitor under ordinary operating conditions”
Setting bit 3 of H98 data at “0” restores the inverter to the measurement in comparison with the initial
capacitance measured at shipment.
When the inverter uses an auxiliary control power input, the load conditions widely differ so that the
discharging time cannot be accurately measured.
In this case, measurement of the discharging time can be disabled with function code H98 (bit 4 = 0) for
preventing unintended measurement.
(2) ON-time counting of DC link bus capacitor
• In a machine system where the inverter main power is rarely shut down, the inverter does not measure the
discharging time. For this reason, a function is also provided to count the length of time that voltage is applied to
main circuit capacitors (main circuit ON time) in order to determine the capacitor life expectancy. (The display
shows the elapsed time “5_26” and lifetime remaining “5_27”. Refer to the “DC link bus capacitor” field in
Table 7.4-2 Life prediction.)
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