Appendix A Trouble-free Use of Inverters (Notes on Electrical Noise)
Appendix-11
Table A.3-2 Examples of noise prevention measures (cont.)
A photoelectric relay
malfunctioned when the inverter
runs the motor.
<Possible cause>
While the inverter is sufficiently
away from the photoelectric
relay, the power source is
connected in common.
Conducted noise has entered
from the power source line.
1) Insert a 0.1 μF capacitor
between the output common
terminal of the amplifier of the
photoelectric relay and the
frame.
1) If a low-current
circuit at the
malfunctioning side
is observed, the
measures may be
simple and
economical.
Proximity
switch
(capacitance
type)
A proximity switch
malfunctioned.
<Possible cause>
The electrostatic capacitive
proximity switch has a low
noise immunity, and is
vulnerable to circuit conducted
noise and radiated noise.
1) Install an LC filter at the
output side of the inverter.
2) Install a capacitive filter at the
input side of the inverter.
3) Ground the 0 V (common)
line of the DC power supply
of the proximity switch
through a capacitor to the box
body of the machine.
1) Noise generated in
the inverter can be
reduced.
2) The switch is
superseded by a
proximity switch of
superior noise
immunity (such as a
magnetic type).
Amplifier for
photoelectric
relay
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