Appendix A Trouble-free Use of Inverters (Notes on electrical noise)
Appendix-9
Table A-2 Examples of Noise Prevention Measures (Continued)
No. Target device
Phenomena Measure
Notes
3 Telephone
(in a
common
private
residence at
a distance of
40 m)
When driving a ventilation fan
with an inverter, noise enters a
telephone in a private
residence at a distance of 40
m.
<Possible cause>
High-frequency leak current of
the inverter and motor flows
into the shielded ground of the
telephone cable on the way
back via the ground of the pole
transformer to cause noise by
electrostatic induction.
1) Connect the ground
terminals of the motors in a
common connection. Return
to the inverter panel, and
insert a 1 μF capacitor
between the input terminal
of the inverter and ground.
1) The effect of the
inductive filter and
LC filter may not
be expected
because of sound
frequency
component.
2) In the case of a
V-connection
power supply
transformer in a
200V system, it is
necessary to
connect capacitors
as shown in the
following figure,
because of
different potentials
to ground.
4 Photo-
electric relay
A photoelectric relay
malfunctioned when the
inverter runs the motor.
[The inverter and motor are
installed in the same place (for
overhead traveling)]
<Possible cause>
Input power line of the inverter
and wiring of the photoelectric
relay run parallel for 30 to 40
m with a spacing of about 25
mm, which invites induction
noise. Due to conditions of the
installation, these lines cannot
be separated.
1) As a temporary measure,
Insert a 0.1 μF capacitor
between the 0 V terminal of
the power supply circuit in
the detection unit of the
overhead photoelectric relay
and a frame of the overhead
panel.
2) As a permanent measure,
move the 24 V power supply
from the ground to the
overhead unit so that
signals are sent to the
ground side with relay
contacts in the ceiling part.
1) Separate the
wiring (30 cm or
more).
2) When separation
is impossible,
signals can be
received and sent
with dry contacts
etc.
3) Do not wire
low-current signal
lines and power
lines in parallel.
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