Measurement Of Main Circuit Voltages, Currents, And Powers; Operation Principle And Application To Electric Meters; Measuring Points And Instruments - Mitsubishi Electric FR-XC-18.5K-PWM Instruction Manual

Measurement of main circuit voltages, currents, and powers

5.2
Measurement of main circuit voltages,
currents, and powers
• Measurement method of voltage and current at each section:
When instruments for commercial frequency are used for measurement, measure the following circuits with the instruments
given below.
• When installing meters etc. on the converter output side:
When the converter-to-inverter wiring length is long, especially in the 400 V class, the meters may generate heat due to
line-to-line leakage current. Therefore, choose the equipment which has enough allowance for the current rating.
• The output voltage across terminals P/+ and N/- on the converter can be measured with a moving-coil type meter (tester).
The voltage varies according to the power supply voltage. The voltage decreases when a load is applied.
Power
supply
Power
supply
Operation principle and application to electric meters
Type Symbol
Moving-coil
Moving-iron
Air-core coil
Measuring points and instruments
152
PRECAUTIONS FOR MAINTENANCE AND INSPECTION
A
W
11
V
U
W A
12
V
V
W A
13
V
W
[Measuring points and instruments example 1]
Dedicated reactor
or
box-type reactor
[Measuring points and instruments example 2]
Operation principle
Uses kinetic energy
generated between the
magnetic field of a permanent
magnet and the current that
flows through the moving-coil.
Uses kinetic energy
generated between the
moving-iron and the magnetic
field of the current that flows
though the fixed coil.
Uses kinetic energy
generated between the
currents that flow through two
different coils.
Dedicated reactor
Multifunction
or
regeneration
box-type reactor
converter
R2/L12
U P/+
S2/L22
V
T2/L32 N/-
W
Multifunction
regeneration
converter
R2/L12 P/+
＋
S2/L22 V
To the Inverter
−
T2/L32 N/-
Measurement Applicable meter
Voltmeter/ammeter/
DC resistance meter/
(Average) thermometer/flux
meter/speed meter
AC
Voltmeter/ammeter
(RMS)
AC/DC Wattmeter/
(RMS) voltmeter/ammeter
＋
V
To the inverter
−
Characteristic
High sensitivity and commonly
used. Energy saving, small
influence of magnetic field.
Strong structure and inexpensive.
Large influence from external
magnetic field, frequency, and
waveform.
Scale is divided equally when
using a wattmeter. Large
influence from external magnetic
field, high energy consumption.
This can be used as a standard
meter for AC and DC.