Hitachi SJ100 Series Instruction Manual page 142

Component Descriptions
AC Reactors, Input Side
This is useful in suppressing harmonics induced on the power supply lines, or when the
main power voltage imbalance exceeds 3% (and power source capacity is more than
500 kVA), or to smooth out line fluctuations. It also improves the power factor.
In the following cases for a general-purpose inverter, a large peak current flows on the
main power supply side, and is able to destroy the inverter module:
• If the unbalanced factor of the power supply is 3% or higher
• If the power supply capacity is at least 10 times greater than the inverter capacity (the
power supply capacity is 500 kVA or more)
• If abrupt power supply changes are expected
Examples of these situations include:
1. Several inverters are interconnected (input side) with a short bus.
2. A thyristor converter and an inverter are interconnected (input side) with a short bus.
3. An installed phase advance capacitor opens and closes.
Where these conditions exist or when the connected equipment must be highly reliable,
install an AC reactor between the power supply and the inverter. Also, where the effects
of an indirect lightning strike is possible, install a lightning conductor.
Example calculation:
V = 205V, V
RS ST
where V is R-S line voltage, V
RS
Unbalance factor of voltage
Please refer to the documentation that comes with the RF noise filter for installation
instructions.
AC Reactors, Output Side
This reactor reduces the vibrations in the motor caused by the inverter's switching
waveforms, by smoothing the waveforms to approximate commercial power quality. It is
also useful when wiring from the inverter to the motor is more than 10m in length, to
reduce reflected voltage wave phenomenon. Please refer to the documentation that
comes with the RF noise filter for installation instructions.
= 203V, V = 197V,
TR
is S-T line voltage, V
ST
Max. line voltage (min.) Mean line voltage
= -----------------------------------------------------------------------------------------------------------
(
V – V + V + V
RS RS ST
= ------------------------------------------------------------------ -
(
V + V + V
RS ST TR
SJ100 Inverter
is T-R line voltage
TR
–
Meanline voltage
) 3 ⁄
205 202 –
TR
×
100 = ----------------------- -
) 3 ⁄
202
5–3
×
100
×
100 = 1.5%