2-26
D Countermeasures Against Radio Interference
Radio
noise is generated from the Inverter as well as the input
and output lines. T
o reduce radio noise,
install
noise filters on both input and output sides, and also install the Inverter in a totally enclosed steel
box. The cable between the Inverter and the motor should be as short as possible.
Power
supply
Noise
filter
Noise
filter
Steel box
Metal pipe
3G3HV
D Cable Length between Inverter and Motor
As
the cable length between the Inverter and the motor
is increased, the floating capacity between the
Inverter
outputs and the ground is increased proportionally
. The increase in floating capacity at the In
-
verter outputs causes the high-frequency leakage current to increase, and this may adversely affect
peripheral
devices and the current detector in the Inverter
’
s output section. T
o prevent this from occur
-
ring,
use a cable of no more than 100 meters between the Inverter and the motor
. If the cable must
be
longer
than 100
meters, take measures to reduce the floating capacity by not wiring in metallic ducts, by
using a separate cable for each phase, and so on.
Also
adjust the carrier frequency according to the cable length between the Inverter and the motor
, as
shown in the table below.
Cable length 50 m max. 100 m max. More than 100 m
Carrier frequency (n050) 15 kHz max (6 max.) 10 kHz max. (4 max.) 5 kHz max. (2 max.)
Note The carrier frequency setting range varies depending on the Inverter capacity.
200-V class, 22 kW max.; 400-V class, 22 kW max.: 0.4 to 15.0 kHz
200-V class, 30 to 75 kW; 400-V class, 30 to 160 kW: 0.4 to 10.0 kHz
400-V class, 185 to 300 kW: 0.4 to 2.5 kHz
D Single-phase Motors Cannot Be Used
The Inverter is not suited for the variable speed control of single-phase motors.
Single-phase
motors are either capacitor start motors or split-phase start
motors. (The method for de
-
termining
rotation direction at startup is dif
ferent.) If a capacitor start motor is used, the capacitor may be
damaged
by a sudden electric discharge caused by Inverter output. If a split-phase start motor is used,
the starting coil may burn because the centrifugal switch does not operate.
Installation Chapter 2
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