1.3 Precautions for Using Inverters
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1.3.3 Precautions for connection of peripheral equipment
[ 1 ] Phase-advancing capacitors for power factor correction
Do not mount a phase-advancing capacitor for power factor correction in the inverter's input (primary) or output
(secondary) circuit. Mounting it in the input (primary) circuit takes no effect.
To correct the inverter power factor, use a DC reactor (DCR) (option). Mounting it in the output (secondary) circuit
causes an overcurrent trip, disabling operation.
An overvoltage trip that occurs when the inverter is stopped or running with a light load is assumed to be due to
surge current generated by open/close of phase-advancing capacitors in the power system. The use of a DC reactor
(DCR) or AC reactor (ACR) (options) is recommended as a measure to be taken at the inverter side.
Inverter input current to an inverter contains harmonic components that may affect other motors and phase-
advancing capacitors on the same power supply line. If the harmonic components cause any problems, connect a
DCR/ACR to the inverter.
In some cases, it is necessary to insert a reactor in series with the phase-advancing capacitors.
[ 2 ] Power supply lines (application of DC/AC reactors)
Use a DC reactor (DCR) when the capacity of the power supply transformer is 500 kVA or more and is 10 times or
more the inverter rated capacity or when there are thyristor-driven loads. If no DCR is used, the percentage-
reactance of the power supply decreases, and harmonic components and their peak levels increase. These factors
may break rectifiers or capacitors in the converter section of the inverter, or decrease the capacitance of the
capacitors.
If the input voltage interphase unbalance ratio is between 2% and 3%, use an AC reactor.
Interphase unbalance ratio [%]
= (Max. voltage [V] - min. voltage [V]) / Three-phase average voltage [V] × 67 (see IEC/EN61800-3)
[ 3 ] DC reactor (DCR) for correcting the inverter input power factor (for suppressing
harmonics)
To correct the inverter input power factor (to suppress harmonics), use a DCR. Using a DCR increases the reactance
of inverter’s power source so as to decrease harmonic components on the power source lines and correct the power
factor of the inverter.
DCR2/4-/A/B
DCR2/4-C
Approx. 90% to 95%
Approx. 86% to 90%
The last letter identifies the capacitance.
Only selectable for 37 kW or higher models.
- Select a DCR matching not the inverter capacity but the rated capacity of the applied motor.
Applicable reactors differ depending upon the selected HHD or HND specification, even on the same
type of inverters.
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