Measurement Of Main Circuit Voltages, Currents And Powers - Mitsubishi Electric FREQROL HC Instruction Manual

3.2.4 Measurement of main circuit voltages, currents and powers

• Measurement of voltages and currents
When instruments for commercial frequency are used for measurement, measure the following circuits
using the following instruments.
• When installing instruments, etc. on the high power factor converter output side
When the wiring distance is long between the high power factor converter and inverter, the instruments
may generate heat due to line leakage currents in especially 400V class. Select the devices which have
large enough current rating.
• There is an output voltage across terminals P-N of the high power factor converter and this voltage can be
measured by a moving-coil instrument (tester). This voltage varies with the power supply voltage and
reduces when load is applied.
Power supply
Power supply
• Classification and Application of Indicating Electric Instruments by Operation Principle
Type Symbol
Moving-coil type
Moving-iron type
Electrodynamic Air
type core
Reactor 1
A
W
U
11
V
U
A
W
12 V
V
V
A
W
W
13
V
W
<Typical Measuring Points and Instruments>
External box
Reactor 1
Recommended: YOKOGAWA251
Digital power meter
(Can measure voltage, current,
power and power factor)
<Typical Measuring Points and Instruments>
Principle
Uses force working between the
magnetic field of a permanent
magnet and a current flowing in
the moving coil.
Uses force working between the
magnetic field of a current flowing
in the fixed coil and the moving
iron.
Uses force working between
currents flowing in two coils.
External box
Converter
Reactor 2
R4
S4
T4
Converter
Reactor 2
R4
P
S4
T4
N
Applied
Indication
Instrument
Voltmeter,
ammeter,
resistance
DC
meter,
(Mean value)
thermometer,
flux meter,
speed meter
AC Voltmeter,
(Effective value) ammeter
Wattmeter,
AC/DC
voltmeter,
(Effective value)
ammeter
- 50 -
P
+
V
To inverter
-
N
+
V
To inverter
-
Features
High in sensitivity and most often
used. Power consumption small,
rarely affected by
magnetic field.
Rigid in structure and low in price.
Greatly affected by external
magnetic field, frequency
waveform.
Wattmeter is graduated equally.
Affected by external magnetic field
and consumes large power. May
be used as a standard AC/DC
instrument.
external
and