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Main circuit terminals
1.2.10 Power supply harmonics
The inverter may generate power supply harmonics from its converter circuit to affect
the power generator, power capacitor etc. Power supply harmonics are different from
noise and leakage currents in source, frequency band and transmission path. Take the
following countermeasure suppression techniques.
The following table indicates differences between harmonics and noise:
Item Harmonics Noise
Frequency
Normally 40th to 50th degrees or less
(up to 3kHz or less)
High frequency (several 10kHz
to 1GHz order)
Environment To-electric channel, power impedance To-space, distance, wiring path
Quantitative
understanding
Theoretical calculation possible
Random occurrence,
quantitative grasping difficult
Generated amount Nearly proportional to load capacity
Change with current variation
ratio (larger as switching speed
increases)
Affected equipment
immunity
Specified in standard per equipment
Different depending on maker's
equipment specifications
Suppression example Provide reactor. Increase distance.
Suppression technique
Harmonic currents produced
on the power supply side by
the inverter change with such
conditions as whether there
are wiring impedances and a
power factor improving reactor
(FR-BEL(-H) or FR-BAL(-H))
and the magnitudes of output
frequency and output current
on the load side.
For the output frequency and output current, we understand that they should be
calculated in the conditions under the rated load at the maximum operating frequency.
CAUTION
The power factor improving capacitor and surge suppressor on the inverter
output side may be overheated or damaged by the harmonic components of the
inverter output. Also, since an excessive current flows in the inverter to activate
overcurrent protection, do not provide a capacitor and surge suppressor on the
inverter output side when the motor is driven by the inverter. To improve the
power factor, insert a power factor improving reactor on the inverter's primary
side or DC circuit. For full information, refer to page 17.
Inverter
NFB
Do not provide power factor
improving capacitor.
Motor
IM
FR-BEL(-H)
FR-BAL(-H)
FR-BAL
FR-BEL