Measurement Of Powers; Measurement Of Voltages And Use Of Pt; Measurement Of Currents; Use Of Ct And Transducer - Mitsubishi Electric 800 Series Instruction Manual

*3 Terminal T/L3 is provided only on the three-phase power input model.
3.2.1

Measurement of powers

Use digital power meters (for inverter) both on the inverter's input and output sides.
3.2.2

Measurement of voltages and use of PT

 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 as 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.
3.2.3

Measurement of currents

Use a digital power meter (for inverter) both on the inverter's input and output sides.
Since the inverter 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.
3.2.4

Use of CT and transducer

Use digital power meters (for inverter) both on the inverter's input and output sides.
Since the inverter 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.
3.2.5

Measurement of inverter input power factor

Calculate the factor from the effective power and the apparent power. A power-factor meter cannot indicate an exact value.
[Three-phase power supply]
Total power factor of the inverter =
[Single-phase power supply]
Total power factor of the inverter =
3.2.6 Measurement of converter output voltage (between
terminals P and N)
The output voltage of the converter can be measured with a voltmeter (such as a digital multimeter) between terminals P and
N. The voltage varies according to the power supply voltage. Approximately 270 to 300 V for the 200 V class, approximately
540 to 600 V for the 400 V class, and approximately 800 to 900 V for the 575 V class is output when no load is connected. The
voltage decreases when a load is applied.
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3. Precautions for Maintenance and Inspection
3.2 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)
Effective power
Apparent power
Three-phase input power found by the 3-wattmeter method
=
V (power supply voltage) × I (input current effective value)