Fuji Electric frenic mini series - Page 270

App. A Advantageous Use of Inverters (Notes on electrical noise)
A-9
App.
Table A.2 Continued
No.
Target
device
Phenomena Noise prevention measures
Notes
1) Connect the ground
terminals of the motors in
a common connection.
Return to the inverter
panel, and insert a 1 PF
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
230V system, it is
necessary to
connect
capacitors as
shown in the
following figure,
because of
different
potentials to
ground.
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3 Tele-
phone
(in a
common
private
residence
at a
distance
of 131 ft
(40 m))
When driving a ventilation
fan with an inverter, noise
enters a telephone in a private
residence at a distance of 131
ft (40m).
<Possible cause>
A high-frequency leakage
current from the inverter and
motor flowed to grounded
part of the telephone cable
shield. During the current's
return trip, it flowed through
a grounded pole transformer,
and noise entered the
telephone by electrostatic
induction.
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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)]
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<Possible cause>
It is considered that induction
noise entered the
photoelectric relay since the
inverter's input power supply
line and the photoelectric
relay's wiring are in parallel
separated by approximately
0.98 in (25 mm) over a
distance of 98 to 131 ft (30 to
40 m). Due to conditions of
the installation, these lines
cannot be separated.
1) As a temporary measure,
Insert a 0.1PF 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.
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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.
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1) The wiring is
separated by
more than 11.81
in (30 cm).
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2) When separation
is impossible,
signals can be
received and sent
with dry contacts
etc.
3) Do not wire
weak-current
signal lines and
power lines in
parallel.
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