Fuji Electric Frenic Mega Series - Page 707

App. A Advantageous Use of Inverters (Notes on Electrical Noise)
A-11
App.
No.
Tar ge t
device
Problem Noise prevention
Notes
7
Pressure
sensor
The pressure sensor
malfunctioned.
Figure A-25
<Possible cause>
The pressure sensor may
malfunction due to noise that came
from the box body through the
shielded wire.
1) Install an LC filter at the input
side of the inverter.
2) Disconnect the shielded cable
for the pressure sensor from
the machine enclosure to the
pressure sensor 0 V line
(common mode).
Figure A-26
1) Connect the
shielded wire for the
sensor signal to the
common point of the
system.
2) Reduce the
conductive noise
from the inverter.
8
Position
detector
(pulse
generator)
The crane stop position got
misaligned due to a wrong pulse
from the pulse converter.
Figure A-27
<Possible cause>
The motor power cable and pulse
generator signal wire are cabled
together and the inductive noise
may cause wrong 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.
Figure A-28
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.
Figure A-29
<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 at the
output side of the inverter.
3) Lower the carrier frequency of
the inverter.
Figure A-30
1) Total conduction
noise and induction
noise in the electric
line can be reduced.