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App. A Advantageous Use of Inverters (Notes on electrical noise)
A-3
App.
[ 2 ] Types of noise
Noise generated in an inverter is propagated through the main circuit wiring to the power supply and
the motor so as to affect a wide range of applications from the power supply transformer to the
motor. The various propagation routes are shown in Figure A.2. According to those routes, noises
are roughly classified into three types--conduction noise, induction noise, and radiation noise.
Figure A.2 Noise Propagation Routes
(1) Conduction noise
Noise generated in an inverter may propagate through the conductor and power supply so as to affect
peripheral devices of the inverter (Figure A.3). This noise is called "conduction noise." Some
conduction noises will propagate through the main circuit
. If the ground wires are connected to a
common ground, conduction noise will propagate through route . As shown in route , some
conduction noises will propagate through signal lines or shielded wires.
Figure A.3 Conduction Noise
(2) Induction noise
When wires or signal lines of peripheral devices are brought close to the wires on the input and
output sides of the inverter through which noise current is flowing, noise will be induced into those
wires and signal lines of the devices by electromagnetic induction (Figure A.4) or electrostatic
induction (Figure A.5). This is called "induction noise"
.
Figure A.4 Electromagnetic Noise