Measurement Of Main Circuit Voltages, Currents And Power - Mitsubishi Electric FR-CV-7.5K Instruction Manual

Precautions for Maintenance and Inspection
3.2.8

Measurement of main circuit voltages, currents and power

Measurement of voltages and currents
When instruments for commercial frequency are used for measurement, measure the following circuits using the
instruments given below.
When installing measuring instruments etc. on the output side of the power regeneration common converter,
choose the measuring instruments that have allowance in current rating since they may generate heat under the
influence of line-to-line leakage currents if the wiring distance between the power regeneration common converter
and inverter is long.
The DC voltage, which is developed across the terminals P/L+ and N/L- of the power regeneration common
converter, can be measured with a moving-coil instrument (tester). Though it varies with the power supply voltage,
the voltage will reduce under load.
Power
supply
Classification and application by the operation principles of electrical indicator
instruments
Type Symbol
Moving-coil type
Moving-iron type
Electrodyn
Air
amometer
core
type
Item
Power supply voltage V
1
Power supply side current
I
1
Dedicated
stand-alone
W11 Au
Vu
W12
Av
Vv
W13
Aw
Vw
< Typical Measuring Points and Instruments >
Principle
Utilizes the force that
works between the
magnetic field of the
permanent magnet and the
current flowing in the
moving coil.
Utilizes the force that is
produced between the
magnetic field of the
current flowing in the fixed
coil and the moving iron.
Utilizes the force that
works between the
currents flowing in two
coils.
Measuring Points and Instruments
Measuring Point
Across R2/L1-S2/L2, S2/L2-
T2/L3, and T2/L3-R2/L1
R2/L1, S2/L2 and T2/L3 line
currents
Power regeneration
common converter
reactor
R2/L1 P/L+
S2/L2
T2/L3 N/L-
Applicable
Indication
Instrument
Voltmeter,
ammeter,
DC resistance
(Average meter,
value) thermometer,
flux meter,
rotating meter
AC
Voltmeter,
(Effective
ammeter
value)
AC/DC Wattmeter,
(Effective Voltmeter,
value) ammeter
Measuring Instrument
Moving-iron type AC
voltmeter
Moving-iron type AC
ammeter
40
+
To inverter
V
-
Features
High in sensitivity and most often
used. Affected little by consumed
power and external magnetic field.
Rigidly structured and low priced.
Affected greatly by external
magnetic field, frequency and
waveform.
A wattmeter is graduated equally.
Affected greatly by external
magnetic field and large in power
consumption. Usable as an AC/DC
standard instrument.
Remarks
(Reference Measured Value) *
Commercial power supply
Within permissible AC voltage
fluctuation (Refer to page 44)