Hitachi WJ200 Series Instruction Manual page 50

WARNING: In the cases below involving a general-purpose inverter, a large peak
current can flow on the power supply side, sometimes destroying the converter module:
1. The unbalance factor of the power supply is 3% or higher.
2. The power supply capacity is at least 10 times greater than the inverter capacity
(or the power supply capacity is 500kVA or more).
3. Abrupt power supply changes are expected, due to conditions such as:
a. Several inverters are interconnected with a short bus.
b. A thyristor converter and an inverter are interconnected with a short bus.
c. An installed phase advance capacitor opens and closes.
Where these conditions exist or when the connected equipment must be highly reliable,
you MUST install an input-side AC reactor of 3% (at a voltage drop at rated current)
with respect to the supply voltage on the power supply side. Also, where the effects of
an indirect lightning strike are possible, install a lightning conductor.
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