Hitachi SJ700D-004L, Instruction Manual

Page: 255 / 288

Chapter6 Maintenance and Inspection
6-6
6.8 Methods of Measuring the Input/Output Voltages, Current, and Power
This section describes the measuring instruments generally used to measure the input and output voltages, output
current, and output power of the inverter.
I
R
I
S
I
T
E
R
E
T
E
S
W
I2
W
I3
W
I1
R
T
S
U
V
W
I
U
I
V
I
W
E
U
E
W
E
V
W
O2
W
O1
W
V
U R
S
T
Power supply
Inv
ert
er
Motor
Measurement item Measuring point Measuring instrument Remarks Reference values
Input voltage (E
IN
) Across R-S, S-T, and T-R
(E
R
), (E
S
), and (E
T
)
Moving-iron voltmeter
or
rectifier-type voltmeter Effective value of full
waves 200 V class models:
200 to 240 V, 50/60 Hz
400 V class
380 to 480 V, 50/60 Hz
Input current (I
IN
) Current at R, S, and T
(I
R
), (I
S
), and (I
T
)
Moving-iron ammeter Effective value of full
waves When input currents are
unbalanced
I
IN
= (I
R
+ I
S
+ I
T
)/3
Input power (W
IN
) Across R-S, S-T, and T-R
(W
11
) + (W
12
) + (W
13
)
Electrodynamometer-type
wattmeter Effective value of full
waves 3-wattmeter method
input power factor
(Pf
IN
)
Calculated from the measured input voltage (E
IN
), input current (I
IN
), and input power (W
IN
)
Output voltage
(E
OUT
)
Across U-V, V-W, and W-U
(E
U
), (E
V
), and (EW)
Method shown in the figure
below
or
rectifier-type voltmeter Effective value of
fundamental wave
Output current
(I
OUT
)
Current at U, V, and W
(I
U
), (IV), and (IW)
Moving-iron ammeter Effective value of full
waves
Output power
(W
OUT
)
Across U-V and V-W
(W
01
) + (W
02
)
Electrodynamometer-type
wattmeter Effective value of full
waves 2-wattmeter method
(or 3-wattmeter method)
Output power
factor (Pf
OUT
)
Calculated from the measured input
voltage (E
OUT
), input current (I
OUT
), and
input power (W
OUT
)
Notes:
1. To measure the output voltage, use an
instrument that reads the effective
value of the fundamental wave. To
measure the current or power, use an
instrument that reads the effective
value of full waves.
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
testers may be inapplicable for the
measurement because of the adverse
effect of noise.
Method to measure the output voltage
R
T
S
Inv
erter
U
V
W
Motor
+
－
V
DC
2W 220
ｋ

Diode
600 V, 0.1 A or more
(200 V class model)
1,000 V, 0.1 A or more
(400 V class model)
Effective value of
fundamental wave (V
AC
)
V
AC
= 1.1 x V
DC
Moving-coil voltmeter
300 V (200 V class
model)
600 V (400 V class
model)
Pf
IN=
W
IN
√3
・
E
IN
・
I
IN
×100 (%)
Pf
OUT
=
W
OUT
√3
・
E
OUT
・
I
OUT
×100 (%)