Appendix A Trouble-free Use of Inverters (Notes on Electrical Noise)
Appendix-12
Table A.3-2 Examples of noise prevention measures (cont.)
A pressure sensor
malfunctioned.
<Possible cause>
Noise enters from the box body
via the shielded wire to cause
malfunctioning of the pressure
sensor.
1) Install an LC filter on the
input side of the inverter.
2) Connect the shield of the
shielded wire of the pressure
sensor to the 0 V line
(common) of the pressure
sensor, changing the original
connection.
1) The shielded parts
of shield wires for
sensor signals are
connected to a
common point in
the system.
2) Conductive noise
from the inverter
can be reduced.
Position
detector (pulse
encoder)
Erroneous-pulse outputs from a
pulse converter caused a shift
in the stop position of a crane.
<Possible cause>
The motor power line and the
signal line for the encoder are
wired together in a bundle. This
produces induction noise to
cause output of error pulses.
1) Install an LC filter and a
capacitive filter at the input
side of the inverter.
2) Install an LC filter at the
output side of the inverter.
1) This is an example
of a measure where
the power line and
signal line cannot
be separated.
2) Induction noise and
radiated noise at
the output side of
the inverter can be
reduced.
Programmable
logic controller
(PLC)
The PLC program sometimes
malfunctions.
<Possible cause>
Power sources of the inverter
and PLC are in the same
system so that noise enters
PLC via the power source.
1) Install a capacitive filter and
an LC filter on the input side
of the inverter.
2) Install an LC filter on the
output side of the inverter.
3) Lower the carrier frequency
of the inverter.
1) Total conducted
noise and induction
noise in the electric
line can be
reduced.
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