Fuji Electric FRN355VG1S-4J [1020/1046] A noise

Fuji Electric FRN315VG1S-4J [1020/1046] A noise
A-2
A.2 Noise
This section gives a summary of noises generated in inverters and their effects on devices subject to
noise.
[ 1 ] Inverter noise
Figure A.1 shows an outline of the inverter configuration. The inverter converts AC to DC
(rectification) in a converter unit, and converts DC to AC (inversion) with 3-phase variable voltage
and variable frequency. The conversion (inversion) is performed by PWM implemented by
switching six transistors (IGBT: Insulated Gate Bipolar Transistor, etc), and is used for variable
speed motor control.
Switching noise is generated by high-speed on/off switching of the six transistors. At each
high-speed on/off switching, noise current (i) flows to the ground through stray capacitance (C) of
the inverter, I/O wire and motor. The amount of the noise current is expressed as follows:
i = C·dv/dt
It is related to the stray capacitance (C) and dv/dt (switching speed of the transistors). Further, this
noise current is related to the carrier frequency since the noise current flows each time the transistors
are switched on or off.
In addition to the main circuit of the inverter, the DC-to-DC switching power regulator (DC/DC
converter), which is the power source for the control circuit of the inverter, may be a noise source in
the same principles as stated above.
The frequency band of this noise over the range of several tens of MHz may affect communications
devices such as AM radios, plant radios, and telephones.
Figure A.1 Outline of Inverter Configuration

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