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Precautions for maintenance and inspection
3
PROTECTIVE FUNCTIONS
3.3.8 Measurement of main circuit voltages, currents and powers
• Measurement of voltages and currents
Since the voltages and currents on the inverter power supply and output sides
include harmonics, measurement data depends on the instruments used and
circuits measured.
When instruments for commercial frequency are used for measurement, measure
the following circuits with the instruments given on the next page.
Examples of Measuring Points and Instruments
CAUTION
Use an FFT to measure the output voltages accurately.
A tester or general measuring instrument cannot measure accurately.
:Moving-iron type
:Electrodynamometer
type
:Moving-coil type
:Rectifier type
+-
Ar
As
At
Vr
Vs
Vt
W11
W12
W13
Au
Av
Aw
Vu
Vv
Vw
W21
W22
V
U
V
W
Instrument
types
Inverter
Three-phase
power supply
To motor
Input
voltage
Input
current
Output
voltage
Output
current
Three-phase 200V
power input
Three-phase 400V
power input