Hitachi SH1-900H

6-6
Chapter 6
Inspection and maintenance
6.8 Input/output voltage, current
Standard equipment for measuring input/output voltage,
current, and power measurement.
When measuring…
1. To measure the output voltage, use an
instrument that reads the effective
value of the fundamental wave. To
measure the current or the 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
multimeters may be defective for the
measurement, because of the adverse
effects of the noise.
Measured
data
Measuring 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 or
Rectifier-type voltmeter
Effective value
of full waves
400V class:380 to 500V 50/60Hz
Input
current
I
IN
R, S, T current
(I
R
), (I
S
), (I
T
)
Moving-iron ammeter
Effective value
of full waves
If there is unbalance in the input
supply
IIN=(I
R
+I
S
+ I
T
)/3
Input power
W
IN
R-S, S-T, T-R
(W
I1
)+(W
I2
)+(W
I3
)
Electrodynamometer-type wattmeter
Effective value
of full waves
Three-wattmeter method
Input power
factor
Pf
IN
Is calculated from the measured values of the input voltage (E
IN
), input
current (I
IN
) and supply power (W
IN
)
Output
voltage
E
OUT
U-V, V-W, W-U
(E
U
), (E
V
), (E
W
)
Moving-iron voltmeter or
Rectifier-type voltmeter
Effective value
of fundamental
wave
Output
current
I
OUT
U, V, W current
(I
U
), (I
V
), (I
W
)
Moving-iron ammeter
Effective value
of full waves
Output
power
W
OUT
U-V, V-W
(W
O1
)+(W
O2
)
Electrodynamometer-type wattmeter
Effective value
of full waves
Two-wattmeter method
(Otherwise the three-wattmeter
method)
Output
power
factor
Pf
OUT
Is calculated from the measured values of the output voltage (E
OUT
), output
current (I
OUT
) and output power (W
OUT
).
Example method for measuring output voltage
Diode
1000V 0.1A or more (400V class)
R
T
S
Inverter
U
V
W
Motor
Moving-coil voltmeter
600V (400V class)
Effective value of the fundamental wave VAC
VAC＝1.1×VDC
+
－
VDC
2W 220kΩ
Pf
OUT
=
W
OUT
√3×E
OUT
×I
OUT
×100
Pf
IN
=
W
IN
√3×E
IN
×I
IN
×100
I
R
I
S
I
T
E
R
E
T
E
S
Inverter
I
U
I
V
I
W
E
U
E
W
E
V
Motor
R
S
T
Power
Supply
W
I1
W
I2
W
I3
R
S
T
U
V
W
W
O1
W
O2
U
V
W