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The value displayed on the operation panel is the inverter-controlled voltage itself. Hence, that value is accurate and it is
recommended to monitor values using the operation panel. Monitoring values via the operation panel or by outputting the
analog signal is recommended as these values are accurate.
5.2.3
Measurement of currents
Use a digital power meter (for inverter) for the input side of the converter unit (FR-CC2) and the output side of the inverter.
Since the converter unit input current tends to be unbalanced, measurement of three phases is recommended. The correct
value cannot be obtained by measuring only one or two phases. On the other hand, the unbalanced ratio of each phase of the
output current should be within 10%.
The inverter output current can be monitored on the operation panel. The value displayed on the operation panel is accurate
even if the output frequency varies. Hence, it is recommended to monitor values on the operation panel.
5.2.4
Example of measuring converter unit (FR-CC2)
input power factor
Calculate the factor from the effective power and the apparent power. A power-factor meter cannot indicate an exact value.
Total power factor of the converter unit =
5.2.5
Measurement of converter output voltage (between
terminals P and N)
The output voltage of the converter is output across terminals P and N, and can be measured with a voltmeter such as a digital
multimeter. The voltage varies according to the power supply voltage. Approximately 540 to 600 VDC is output when no load
is applied. The voltage decreases when a load is applied.
When energy is regenerated from the motor during deceleration, for example, the converter output voltage rises to nearly 800
to 900 VDC maximum.
5.2.6
Measurement of inverter output frequency
In the initial setting of the FM type inverter, a pulse train proportional to the output frequency is output across the pulse train
output terminals FM and SD on the inverter. This pulse train output can be counted by a frequency counter, or a digital
multimeter can be used to read the mean value of the pulse train output voltage. When a digital multimeter is used to measure
the output frequency, approximately 5 VDC is indicated at the maximum frequency.
For detailed specifications of the pulse train output terminal FM, refer to the FR-A800 Instruction Manual (Function).
In the initial setting of the CA type inverter, a pulse train proportional to the output frequency is output across the analog current
output terminals CA and 5 on the inverter. Measure the current using a digital multimeter.
For detailed specifications of the analog current output terminal CA, refer to the FR-A800 Instruction Manual (Function).
5.2.7
Insulation resistance test using megger
• For the inverter and the converter unit (FR-CC2), conduct the insulation resistance test on the main circuit only as follows
and do not perform the test on the control circuit. (Use a 500 VDC megger.)
104
5. PRECAUTIONS FOR MAINTENANCE AND INSPECTION
5.2 Measurement of main circuit voltages, currents, and powers
Effective power
Apparent power
Three-phase input power found by the 3-wattmeter method
=
√
3 × V (power supply voltage) × I (input current effective value)
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