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Measurement of main circuit voltages,
currents and powers
6
PRECAUTIONS FOR MAINTENANCE AND INSPECTION
6.2 Measurement of main circuit voltages, currents and powers
6.2.1 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.
When installing meters etc. on the inverter output side
When the inverter-to-motor wiring length is large, especially in the 400V class, small-capacity models, the meters
and CTs may generate heat due to line-to-line leakage current. Therefore, choose the equipment which has
enough allowance for the current rating.
When measuring and indicating the output voltage and output current of the inverter, it is recommended to utilize
the AM and CA terminal output function of the inverter.
Examples of Measuring Points and Instruments
+-
Ar
As
At
Vr
Vs
Vt
W11
W12
W13
Au
Av
Aw
Vu
Vv
Vw
W21
W22
V
U
V
W
Inverter
Three
phase
power
supply
To the motor
Instrument
types
Input voltage
Input current
Output voltage
Output current
: Moving-iron type
: Electrodynamometer type
: Moving-coil type
: Rectifier type
R/L1
S/L2
T/L3
P/+
N/-