Hitachi WJ Series

Chapter 16 Maintenance and Inspection
16-2-6
16.2.7 Measurement Methods of I/O Voltage, Current, and Power
 Typical instruments for measuring input/output voltage, current, and power are shown below.
Measurement
data
Measurement point
Measuring instrument
Remarks
Standard reference values
Input
voltage
E
IN
R-S, S-T, T-R
(E
R
), (E
S
), (E
T
)
Moving-iron
voltmeter
Effective
value of full
waves
200 V class: 200 to 240 V 50/60 Hz
400 V class: 380 to 480 V 50/60 Hz
or
Rectifier-type
voltmeter
Input
current
I
IN
R, S, T currents
(I
R
), (I
S
), (I
T
)
Moving-iron
ammeter
*
1
Effective
value of full
waves
If there is unbalance in the input
supply
I
IN
= (I
R
+I
S
+I
T
) / 3
Input power
W
IN
R-S, S-T, T-R
(W
I1
)+(W
I2
)+(W
I3
)
Electrodynamomete
r-type wattmeter
*1
Effective
value of full
waves
Three-wattmeter method
Input power
factor
P
fIN
Calculated from the measured values of the input voltage (E
IN
),
power input current (I
IN
), and input power (W
IN
).
Output
voltage
E
OUT
U-V, V-W, W-U
(E
U
), (E
V
), (E
W
)
See the figure below
or Rectifier-type
voltmeter
*1*2
Effective
value of
fundamental
wave
Output
current
I
OUT
U, V, W currents
(I
U
), (I
V
), (I
W
)
Moving-iron
ammeter
*1*2
Effective
value of full
waves
Output
power
W
OUT
U-V, V-W
(W
O1
)+(W
O2
)
Electrodynamomete
r-type wattmeter
*1*2
Effective
value of full
waves
Two-wattmeter method
(Or three-wattmeter method)
Output
power
factor
P
fOUT
Calculated from the measured values of the output voltage
(E
OUT
), output current (I
OUT
), and output power (W
OUT
).
*1. Use instruments that show the effective value of the fundamental wave for the output voltage and the effective value
of full waves for the current and power.
*2. Since the inverter output waveform is controlled by PWM, it has a large margin of error, especially at low frequencies.
In many cases, general multimeters may be defective for the measurement, because of the adverse effects of the
noise.
I
R
I
S
I
T
E
R
E
T
E
S
R/L1
T/L3
S/L2
Inverter
U/T1
V/T2
W/T3
I
U
I
V
I
W
E
U
E
W
E
V
Motor
W
V
U
R
S
T
Power
supply
W
O1
W
O2
W
I1
W
I2
W
I3
Example method for measuring output voltage
Diode
600 V 0.1 A or more (200 V class)
1000 V 0.1 A or more (400 V class)
R
T
S
Inverter
U
V
W
Motor
Moving-coil voltmeter
300 V (200 V class)
600 V (400 V class)
Effective value of
fundamental wave VAC
VAC = 1.1 × VDC
+
-
VDC
2 W 220 kΩ
P
fIN
=
W
IN
√3・E
IN
・I
IN
× 100
P
fOUT
=
W
OUT
√3・E
OUT
・I
OUT
× 100