Leakage
Current
Between the inputbutput lines of
the
inverter and in the motor,
capacitance
exists and due to this
capadta~
leakage current
flows.
Since amount of leakage
airrent
varies
depending on the
cepecrtance
and canter frequency, leakage current will increase
if
low-noise operation is at-
tempted by higher carrier frequency setting.
It
is necessary
to
take
the
measures indicated below
if
such
ooeration
mode
is reauired.
I
1
._~
-r-
~
(1)
kaga
current
to
grounding
Leakage
current not only flows into the circuits
of
the
inverter itself, but it also flows into the
circuits of other systems through the ground-
ing.
I
I
."urn
Lower the carrier frequency (Pr.72). If the carrier frequency
is
lowered, motor
noise
is in-
creased.
Use
leakage breaker designed for higher harmonic and
surgg,
New Super
NV
series of
Mitsubishi for exarnpb. This allows low noise
operati
(at higher cairier frequency). For
details of leak breaker selection, refer
to
page
128.
(2)
Lea-
current
between
the
Hm
There
are
cases
that an external
thennal
relay is tripped unexpectedly due to higher har-
monic
component of the leakage current generated by the capacitance between the inverter
output
lines.
0
Measures
Use an electronic thermal relay
01
the inverter.
Lower the carrier frequency. This causes increased mtor noise.
To
protect the motor correctly without being affected by the leakage current Ween the
lines, the method to directly detect the motor sensor using a temperature sensor is
pL
recommended.
v
-
116-
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