Measurement Of Electrical Amounts In Main Circuit - Fuji Electric FRENIC-HVAC User Manual

10.4 Measurement of Electrical Amounts in Main Circuit

Because the voltage and current of the power supply (input, primary circuit) of the inverter main
circuit and those of the motor (output, secondary circuit) contain harmonic components, the readings
may vary with the type of the meter. Use meters listed in Table 10.4 when measuring with meters
designed 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
Power factor =
Input (primary) side
Voltage
Ammeter Voltmeter
A , A , A V , V
R S T R
Rectifier or
Moving iron
moving iron
type
type
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.
Electric power (W)
3 × Voltage (V) × Current
Table 10.4 Meters for Measurement of Main Circuit
Current Voltage
Wattmeter
, V W , W A
S T R T
Digital AC Digital AC
power meter power meter

Figure 10.1 Connection of Meters
× 100 %
(A)
Output (secondary) side
Current
Ammeter Voltmeter
, A , A V , V , V
U V W U V W
Digital AC
power meter
 
10-8
DC link bus
voltage
(P(+)-N(-))
Wattmeter DC voltmeter
W , W V
U W
Digital AC Moving coil
power meter type
