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CAUTION: EFFECTS OF POWER DISTRIBUTION SYSTEM ON INVERTER
In the case 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 lightening
strike are possible, install a lightening conductor.
CAUTION: SUPPRESSION FOR NOISE INTERFERENCE FROM INVERTER
The inverter uses many semiconductor switching elements such as transistors and IGBTs. Thus,
a radio receiver or measuring instrument located near the inverter is susceptible to noise
interference.
To protect the instruments from erroneous operation due to noise interference, they should be
used well away from the inverter. It is also effective to shield the whole inverter structure.
The addition of an EMI filter on the input side of the inverter also reduces the effect of noise from
the commercial power line on external devices.
Note that the external dispersion of noise from the power line can be minimized by connecting an
EMI filter on the primary side of the inverter.
SFEF model has integrated filter complies to EN61800-3 category C1.
HFEF model has integrated filter complies to EN61800-3 category C2.
EMI Filter
R1
S1
T1
R2
S2
T2
EMI Filter
L1
L2
L3
U
V
W
Motor
Motor
EMI Filter Inverter
Remote
Operator
Completely ground the
enclosure panel, metal
screen, etc. with as short
a wire as possible.
noise
Grounded frame
Conduit or shielded cable
-- to be grounded
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