Measurement Of Powers; Measurement Of Voltages; Measurement Of Currents; Measurement Of Inverter Input Power Factor - Mitsubishi Electric 800 Series Instruction Manual

Measurement of main circuit voltages, currents and powers
7.2.1

Measurement of powers

Use a digital power meter (for inverter) on the inverter's input side.
7.2.2

Measurement of voltages

Inverter input side
Use a digital power meter (for inverter) on the inverter's input side.
Inverter output side
When using a measuring instrument, use a digital power meter for inverters since the inverter outputs PWM-controlled square
wave voltage. The value monitored on the operation panel is the inverter-controlled voltage itself. Monitoring values via the
operation panel or by outputting the analog signal is recommended as these values are accurate.
7.2.3

Measurement of currents

Use a digital power meter (for inverter) both on the inverter's input and output sides.
Since current on the inverter 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.
7.2.4

Measurement of inverter input power factor

Calculate using effective power and apparent power. A power-factor meter cannot indicate an exact value.
Total power factor of the inverter
7.2.5
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 VDC to 900 VDC 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 VDC to 1300 VDC maximum.
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PRECAUTIONS FOR MAINTENANCE AND INSPECTION
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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