App. A Advantageous Use of Inverters (Notes on electrical noise)
A-11
App.
Table A.2 Continued
No.
Target
device
Phenomena Noise prevention measures
Notes
7
Pressure
sensor
A pressure sensor
malfunctioned.
<Possible cause>
The pressure sensor may
malfunction due to noise that
came from the box housing
through the shielded wire.
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) Conduction
noise from the
inverter can be
reduced.
8
Position
detector
(pulse
generator
: PG)
Erroneous-pulse outputs
from a pulse converter caused
a shift in the stop position of a
crane.
<Possible cause>
Erroneous pulses may be
outputted by induction noise
since the power line of the
motor and the signal line of
the PG are bundled together.
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 radiation
noise at the
output side of the
inverter can be
reduced.
9
Program
mable
logic
controller
(PLC)
The PLC program sometimes
malfunctions.
<Possible cause>
Since the power supply
system is the same for the
PLC and inverter, it is
considered that noise enters
the PLC through the power
supply.
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 conduction
noise and
induction noise
in the electric
line can be
reduced.
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