General Inverter Electrical Measurements - Hitachi L200 Series Service Manual

6–12
Maintenance and Inspection

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.
Parameter
Supply voltage
E
1
Supply current
I
1
Supply power
W
1
Supply power
factor Pf
1
Output voltage
E
0
Output current
I
o
Output power
W
o
Output power
factor Pf
o
Note 1:
Note 2:
Note 3:
Circuit location
of measurement
E – across L1 and L2
R
E – across L2 and L3
S
E – across L3 and L1
T
I – L1, I – L2, I – L3
r s t
W – across L1 and L2
11
W – across L2 and L3
12
Pf
----------------------------- -
=
1
3 E
E – across U and V
U
E – across V and W
V
E – across W and U
W
I – U
U
I – V
V
I – W
W
W – across U and V
01
W – across V and W
02
Calculate the output power factor from the output voltage E,
output current I, and output power W.
Pf
----------------------------- -
=
0
Use a meter indicating a fundamental wave effective value for voltage, and
meters indicating total effective values for current and power.
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.
A general-purpose digital volt meter (DVM) is not usually suitable to measure
a distorted waveform (not pure sinusoid).
Measuring
instrument
Moving-coil Fundamental
type voltmeter or wave effective
rectifier type value
voltmeter
Total effective
value
Total effective
value
W
1
×
100%
× ×
I
1 1
Rectifier type Total effective
voltmeter value
Moving-coil Total effective
ammeter value
Electronic type Total effective
wattmeter value
W
0
×
100%
× ×
3 E I
0 0
Notes Reference Value
Commercial
supply voltage
(200V class) 200–
240V, 50/60 Hz
400V class 380–
460V, 50/60 Hz
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