Mitsubishi Electric FR-A862 Instruction Manual page 80

5.2.1
Measurement of powers
Use a digital power meter (for inverter) for the input side of the converter unit (FR-CC2) and the output side of the inverter.
5.2.2
Measurement of voltages
Converter unit (FR-CC2) input side
Use a digital power meter for inverters for the input side voltage.
Inverter output side
Always use a digital power meter for inverter for measurement as the output side voltage has a PWM-controlled rectangular
wave. The value monitored on the operation panel is the inverter-controlled voltage itself. Hence, that value is accurate and it
is recommended to monitor values (analog output) using the operation panel.
5.2.3
Measurement of currents
Use digital power meters (for converter) for the both of inverter input and output side.
Since current on the converter unit input side tends to be unbalanced, measurement of three phases is recommended.
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 side current should be within 10%.
The inverter output current can be monitored on the operation panel. The value monitored on the operation panel is accurate
if the output frequency varies, and it is recommended to monitor values (provide analog output) using the operation panel.
5.2.4
Example of measuring converter unit (FR-CC2)
input power factor
Calculate using effective power and 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
(across 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. Although the voltage varies according to the power supply voltage, approximately 800 to 900 V is output
when no load is connected and voltage decreases during driving load operation.
When energy is regenerated from the motor during deceleration, for example, the converter output voltage rises to nearly
1100 to 1300 V maximum.
Measurement of main circuit voltages, currents and powers
Effective power
=
Apparent power
Three-phase input power found by the 3-wattmeter method
=
 V (power supply voltage)  I (input current effective value)
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PRECAUTIONS FOR MAINTENANCE AND INSPECTION
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