Hitachi WJ Series User Manual page 409

Chapter 16
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.
R
I
R
S
Power
I
S
supply
T
I
T
Measurement
Measurement point
data
Input
R-S, S-T, T-R
voltage
(E
R
E
IN
Input
R, S, T currents
current
(I ), (I
R
I
IN
R-S, S-T, T-R
Input power
W (W
IN
Calculated from the measured values of the input voltage (E
Input power
power input current (I
factor
P
fIN
Output
U-V, V-W, W-U
voltage
(E
U
E
OUT
Output U, V, W currents
current
(I ), (I
U
I
OUT
Output
U-V, V-W
power
(W
W
OUT
Calculated from the measured values of the output voltage
Output
(E
power
OUT
factor
P
fOUT
*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.
Diode
600 V 0.1 A or more (200 V class)
1000 V 0.1 A or more (400 V class)
Effective value of
fundamental wave VAC
VAC = 1.1 × VDC
W
I1
E
R
W
I2
E
S
W
I3
E
T
Measuring instrument
Moving-iron
voltmeter
or
), (E ), (E )
S T
Rectifier-type
voltmeter
Moving-iron
ammeter
), (I )
S T
Electrodynamomete
r-type wattmeter
)+(W )+(W )
I1 I2 I3
), and input power (W
IN
W
IN
P =
fIN
√3・E
・I
IN
See the figure below
or Rectifier-type
), (E ), (E )
V W voltmeter
Moving-iron
), (I )
V W ammeter
Electrodynamomete
r-type wattmeter
)+(W )
O1 O2
), output current (I ), and output power (W
OUT
W
OUT
P =
fOUT
√3・E
OUT
Example method for measuring output voltage
R U
S
V
T
W
Maintenance and Inspection
R/L1 U/T1
I
U
Inverter
S/L2 V/T2
I
V
T/L3
W/T3
I
W
Remarks
Effective
value of full
waves
Effective
value of full
*
1
waves
Effective
value of full
*1
waves
IN
).
IN
× 100
IN
Effective
value of
fundamental
*1*2
wave
Effective
value of full
*1*2
waves
Effective
value of full
*1*2
waves
).
OUT
× 100
・I
OUT
Motor
2 W 220 kΩ
+
VDC
-
16-2-6
U
W
O1
E
U
V
E
V
W
W
O2
E
W
Standard reference values
200 V class: 200 to 240 V 50/60 Hz
400 V class: 380 to 480 V 50/60 Hz
If there is unbalance in the input
supply
I = (I +I +I ) / 3
IN R S T
Three-wattmeter method
),
Two-wattmeter method
(Or three-wattmeter method)
Moving-coil voltmeter
300 V (200 V class)
600 V (400 V class)
Motor