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PROTECTIVE FUNCTIONS
39
5.3.7 Measurement of main circuit voltages, currents and power
Measurement of voltages and currents
Since the voltages and currents on the inverter power supply and output sides include harmonics,
accurate measurement depends on the instruments used and circuits measured.
When instruments for commercial frequency are used for measurement, measure the following circuits
using the instruments given on the next page.
+-
Ar
As
At
Vr
Vs
Vt
W
11
W
12
W
13
Au
Av
Aw
Vu
Vv
Vw
W
12
W
22
V
R<L
1
>
S<L
2
>
T<L
3
>
U
V
W
Inverter
P<+>
2
<->N
5
3-phase
power
supply
Instrument
types
Input voltage
Input current
Output voltag
e
Output curren
t
To motor
Typical Measuring Points and Instruments
Note: Use an FFT to measure the output voltage accurately. Accurate measurement cannot be made if you
use a tester or general measuring instruments.