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Leakage Current
Between the inputbutput lines of
the
inverter and in the motor, capacitance exists and due to this
c a p a d t a ~
leakage current
fl o ws.
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) k a g a 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
. " u r n
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 ope r a ti (at higher cairier frequency). For
details of leak breaker selection, refer to page 128.
(2)
L e a -
current
between the
H m
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 m t o r noise.
To protect the motor correctly without being affected by the leakage current W e e n the
lines, the method to directly detect the motor sensor using a temperature sensor is
recommended.
-
116-
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