Hitachi SJ100 Series - General Inverter Electrical Measurements

SJ100 Inverter
Troubleshooting
and Maintenance
6–11
General Inverter Electrical Measurements
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.
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).
Parameter
Circuit location
of measurement
Measuring
instrument
Notes Reference Value
Supply voltage
E
1
E
R
– across L1 and L2
E
S
– across L2 and L3
E
T
– across L3 and L1
Moving-coil
type voltmeter or
rectifier type
voltmeter
Fundamental
wave effective
value
Commercial
supply voltage
(200V class) 200-
240V, 50/60 Hz
400V class 380-
460V, 50/60 Hz
Supply current
I
1
I
r
– L1, I
s
– L2, I
t
– L3 Total effective
value
—
Supply power
W
1
W
11
– across L1 and L2
W
12
– across L2 and L3
Total effective
value
—
Supply power
factor Pf
1
—
Output voltage
E
0
E
U
– across U and V
E
V
– across V and W
E
W
– across W and U
Rectifier type
voltmeter
Total effective
value
—
Output current
I
o
I
U
– U
I
V
– V
I
W
– W
Moving-coil
ammeter
Total effective
value
—
Output power
W
o
W
01
– across U and V
W
02
– across V and W
Electronic type
wattmeter
Total effective
value
—
Output power
factor Pf
o
Calculate the output power factor from the output voltage E,
output current I, and output power W.
—
Pf
1
W
1
3E
1
× I
1
×
------------------------------
100%×=
Pf
0
W
0
3E
0
× I
0
×
------------------------------
100%×=