Fuji Electric FRENIC-MEGA, Instruction Manual

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7-6
Ch
ap
. 7
MAINTENAN
C
E AND
INSPE
C
T
ION
7.4 Measurement of Electrical Amounts in Main Circuit
Because the voltage and current of the power supply (input, primary circuit) of the main circuit of the inverter and those of the motor
(output, secondary circuit) contain harmonic components, the readings may vary with the type of the meter. Use meters indicated in
Table 7.4 when measuring with meters for commercial frequencies.
The power factor cannot be measured by a commercially available power-factor meter that measures the phase difference between
the voltage and current. To obtain the power factor, measure the power, voltage and current on each of the input and output sides and
use the following formula.
„
Three-phase input
% 100 ×
(A) Current × (V) Voltage × 3
(W) power Electric
= factor Power
Table 7.4 Meters for Measurement of Main Circuit
It
e
m
Input (primary) side Output (secondary) side
DC link bus
voltage
(P(+)-N(-))
Wa
v
e
fo
rm
Voltage Current Voltage Current
Name
of meter
Ammeter
AR, AS, AT
Voltmeter
VR, VS, VT
Wattmeter
WR, WT
Ammeter
AU, AV, AW
Voltmeter
VU, VV, VW
Wattmeter
WU, WW
DC voltmeter V
T
ype
of
met
er
Moving iron
type
Rectifier or
moving iron
type
Digital
AC power
meter
Digital AC
power meter
Digital AC
power meter
Digital AC
power meter
Moving coil
type
Symbol
of m
e
te
r
⎯ ⎯ ⎯ ⎯
It is not recommended that meters other than a digital AC power meter be used for measuring the output voltage or output
current since they may cause larger measurement errors or, in the worst case, they may be damaged.
Figure 7.1 Connection of Meters