Appendix A Trouble-free Use of Inverters (Notes on Electrical Noise)
Appendix-10
Table A.3-2 Examples of noise prevention measures (cont.)
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 200 V system,
it is necessary to
connect capacitors
as shown in the
following figure,
because of different
potentials to
ground.
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.
Photoelectric relay
(24V)
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