Use Of Ct And Transducer; Measurement Of Inverter Input Power Factor; Measurement Of Converter Output Voltage (Across Terminals P/+ And N/-) - Mitsubishi Electric FR-A700 Instruction Manual

Meters and measuring methods
7.7.4

Use of CT and transducer

A CT may be used in both the input and output sides of the inverter, but the one used should
have the largest possible VA ability because an error will increase if the frequency gets lower.
When using a transducer, use the effective value calculation type which is immune to har-
monics.
7.7.5

Measurement of inverter input power factor

Use the effective power and apparent power to calculate the inverter input power factor. A
power-factor meter cannot indicate an exact value.
Total power factor of the inverter
7.7.6 Measurement of converter output voltage (across terminals P/+ and N/–)
The output voltage of the converter is developed across terminals P/+ - N/− and can be meas-
ured with a moving-coil type meter (tester). Although the voltage varies according to the power
supply voltage, approximately 540 V to 600 V is output when no load is connected and voltage
decreases when a load is connected. When regenerative energy is returned from the motor dur-
ing deceleration, for example, the converter output voltage rises to nearly 800 V to 900 V max-
imum.
7 - 34
Effective power
= ----------------------------------------- -
Apparent power
3-phase input power found by 3-wattmeter method
= -------------------------------------------------------------------------------------------------------------------------------------------------------------------- -
×
3 V (power supply voltage
×
I (input current effective value)
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