General Inverter Electrical Measurements
Parameter
Supply voltage
Supply current
Supply power
Supply power
factor Pf
Output voltage
Output current
Output power
Output power
factor Pf
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Technologies Inc.
The following table specifies how to measure key system electrical parameters. The
diagrams on the next page show inverter-motor systems and the location of measurement
points for these parameters.
Circuit location
of measurement
E
– across L1 and L2
R
E
E
– across L2 and L3
1
S
E
– across L3 and L1
T
I
– L1, I
– L2, I
r
s
I
1
W
– across L1 and L2
11
W
W
– across L2 and L3
1
12
Pf
1
E
– across U and V
U
E
E
– across V and W
0
V
E
– across W and U
W
I
– U
U
I
I
– V
o
V
I
– W
W
W
– across U and V
01
W
W
– across V and W
o
02
Calculate the output power factor from the output voltage E,
output current I, and output power W.
o
Pf
Note 1:
Use a meter indicating a fundamental wave effective value for voltage, and meters indicating
total effective values for current and power.
Note 2:
The inverter output has a distorted waveform, and low frequencies may cause erroneous
readings. However, the measuring instruments and methods listed above provide comparably
accurate results.
Note 3:
A general-purpose digital volt meter (DVM) is not usually suitable to measure a distorted
waveform (not pure sinusoid).
Measuring
instrument
Moving-coil
type voltmeter or
rectifier type
voltmeter
– L3
t
W
1
=
----------------------------- -
100%
1
3
E
I
1
1
Rectifier type
voltmeter
Moving-coil
ammeter
Electronic type
wattmeter
W
0
----------------------------- -
=
100%
0
3
E
I
0
0
L100 Inverter
Notes
Reference Value
Fundamental
Commercial
wave effective
supply voltage
value
(200V class) 200-
240V, 50/60 Hz
400V class 380-
460V, 50/60 Hz
Total effective
—
value
Total effective
—
value
—
Total effective
—
value
Total effective
—
value
Total effective
—
value
—
6–11