Mitsubishi Electric FR-D720S SC EC, Инструкция по эксплуатации, Страница: 470 / 512

Meters and measuring methods Troubleshooting
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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 harmonics.
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.
7.7.6 Measurement of converter output voltage (across terminals P/+ and N/–)
The output voltage of the converter is developed across terminals P/+ and N/– and can be meas-
ured with a moving-coil type meter (tester). Although the voltage varies according to the power
supply voltage, approximately 270V DC to 300V DC (540V DC to 600V DC for the 400V class)
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 out-
put voltage rises to nearly 400V DC to 450V DC (800V DC to 900V DC for the 400V class) max-
imum. When this value is reached the alarm message E.OV
is displayed and the inverter out-
put is shut off.
Total power factor of the inverter
Effective power
Apparent power
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3-phase input power found by 3-wattmeter method
3 V (power supply voltage)
×
I (input current effective value)
×
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