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6
PRECAUTIONS FOR MAINTENANCE AND INSPECTION
Measurement of main circuit voltages, currents and powers
6.2 Measurement of main circuit voltages, currents and powers
Since the voltages and currents on the drive unit 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 drive unit output side
When the drive unit-to-motor wiring length is large 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.
To measure and display the output voltage and output current of the drive unit, it is recommended to use the FM-SD
terminal output function of the drive unit.
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
Drive unit
Three-phase
power supply
To the motor
Instrument types
: Moving-iron type
: Electrodynamometer type
: Moving-coil type
: Rectifier type
R/L1
S/L2
T/L3
P/+
N/-
Input voltage
Input current
Output voltage
Output current