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2.3 Other Wiring
2.3 Other Wiring
2.3.1 Power supply harmonics
Power supply harmonics may be generated from the converter section of the inverter,
affecting the power supply equipment, power capacitor etc. Power supply harmonics
are different in generation source, frequency band and transmission path from radio
frequency (RF) noise and leakage currents. Take the following measures.
# # # # The differences between harmonics and RF noises are indicated below:
Item
Frequency
Environment
Quantitative
understanding
Generated amount
Immunity of affected
device
Examples of
safeguard
# # # # Countermeasures
The harmonic current generated from the
inverter
to
the
according to various conditions such as the
wiring impedance, whether a power factor
improving reactor is used or not, and output
frequency and output current on load side.
For the output frequency and output current,
the adequate method is to obtain them
under rated load at the maximum operating
frequency.
Note: A power factor improving capacitor and surge suppressor on the inverter's
output side may overheat or be damaged due to the harmonics of the inverter
output. Also, when an overcurrent flows in the inverter, the overcurrent
protection is activated. Hence, when the motor is driven by the inverter, do
not install a capacitor or surge suppressor on the inverter's output side. To
improve the power factor, insert a power factor improving reactor in the
inverter's input or DC circuit. For details, refer to the FR-A500/E500 series
technical information.
Harmonics
Normally 40 to 50th degrees,
3kHz or less
To wire paths, power
impedance
Logical computation is
possible
Approximately proportional
to load capacity
Specified in standards for
each device.
Install a reactor.
power
supply
differs
INSTALLATION AND WIRING
High frequency (several 10kHz to MHz
order)
Across spaces, distance, laying paths
Occurs randomly, quantitative
understanding is difficult.
According to current fluctuation rate
(larger with faster switching)
Differs according to maker's device
specifications.
Increase the distance.
NFB
Power factor
improving AC
reactor
31
RF Noise
Power factor
improving DC
reactor
Motor
IM
Do not insert power
factor improving capacitor
2
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