Measurement of main circuit voltages, currents and powers
PRECAUTIONS FOR MAINTENANCE AND INSPECTION
107
5
∗1
Use an FFT to measure the output voltage accurately. A tester or general measuring instrument cannot measure accurately.
∗2
When the carrier frequency exceeds 5 kHz, do not use this instrument since using it may increase eddy current losses produced in metal parts
inside the instrument, leading to burnout. In this case, use an approximate-effective value type.
∗3
When the setting of
Pr.195 ABC1 terminal function selection
is the positive logic
∗4
A digital power meter (designed for inverter) can also be used to measure.
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 digital power meters (for inverters) for the input side voltage.
Inverter output side
When using a measuring instrument, use a digital power meter for inverters as the inverter outputs PWM-controlled square
wave voltage.
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.
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 using effective power and apparent power. A power-factor meter cannot indicate an exact value.
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 540 to 600 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 800
to 900 V maximum.
Total power factor of the converter unit
=
Effective power
Apparent power
=
Three-phase input power found by the 3-wattmeter method
×
V (power supply voltage)
×
I (input current effective value)
3
Summary of Contents for FR-A842-07700
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