Fuji Electric FRENIC-HVAC User Manual page 466

 Capacitance measurement of DC link bus capacitor (H42)
Calculating the capacitance of 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 actual load
conditions are so different from the ones at which the initial/reference capacitance is
measured that the measurement result falls out of the accuracy level required, then the
inverter does not perform measuring.
- The capacitance measuring conditions at shipment are extremely 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 the actual operating conditions are the same as those at shipment, shutting down
the inverter power automatically measures the discharging time; however, if they are
different, no automatic measurement is performed. To perform it, put those conditions back
to the factory default ones and shut down the inverter. For the measuring procedure, see
[ 1 ] given below.
- 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. For the reference capacitance setup procedure, see [ 2 ] on the next page.
Performing the setup procedure automatically detects and saves the measuring conditions
of the DC link bus capacitor.
Setting bit 3 of H98 data to 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,
measuring of the discharging time can be disabled with the function code H98 (Bit 4
= 0) for preventing unintended measuring.
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 such an inverter, the ON-time counting is provided.
If the capacitance measurement is made, the inverter corrects the ON-time according to the
capacitance measured.
The ON-time counting result can be represented as "elapsed time" and "remaining time
before the end of life."
[ 1 ] Measuring the capacitance of DC link bus capacitor in comparison with
initial one at shipment
When bit 3 of H98 data is 0, the measuring procedure given below measures the capacitance
of DC link bus capacitor in comparison with initial one at shipment when the power is turned
OFF. The measuring result can be displayed on the keypad as a ratio (%) to the initial
capacitance.
-------------------------------- Capacitance measuring procedure --------------------------------
1) To ensure validity in the comparative measurement, put the condition of the inverter back
to the state at factory shipment.
• Remove the option card (if already in use) from the inverter.
• In case another inverter is connected via the DC link bus to the P(+) and N(-) terminals
of the main circuit, disconnect the wires. (You do not need to disconnect a DC reactor
(optional), if any.)
• Disconnect power wires for the auxiliary input to the control circuit (R0, T0).
• Turn OFF all the digital input signals fed to terminals [FWD], [REV], and [X1] through
[X7] of the control circuit.
• If a potentiometer is connected to terminal [13], disconnect it.
• If an external apparatus is attached to terminal [PLC], disconnect it.
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