57
3. PRECAUTIONS FOR USE OF THE CONVERTER UNIT
3.2 Power supply harmonics
1
2
3
4
5
6
7
8
9
10
3.2
Power supply harmonics
3.2.1
Power supply harmonics
The inverter or the converter unit may generate power supply harmonics from its converter circuit to affect the power generator,
power factor correction 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.
• Differences between harmonics and noises
• Countermeasures
The harmonic current generated from the inverter or the converter unit to the input side differs according to various
conditions such as the wiring impedance, whether a reactor is used or not, and output frequency and output current on the
load side.
For the output frequency and output current, we understand that this should be calculated in the conditions under the rated
load at the maximum operating frequency.
*1
The converter unit (FR-CC2) has a built-in DC reactor.
NOTE
• 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.
For power factor improvement, install a reactor in the DC circuit of the inverter or the converter unit.
Item
Harmonics
Noise
frequency
Normally 40th to 50th degrees or less (3
kHz or less).
High frequency (several 10 kHz to 1 GHz order).
Location
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 the load capacity.
Changes with the current variation ratio. (Gets
larger as switching speed increases.)
Affected equipment immunity
Specified by standards per equipment.
Different depending on maker's equipment
specifications.
Countermeasure
Provide a reactor.
Increase distance.
DC reactor
∗1
Do not insert power
factor improving capacitor.
MCCB
MC
Inverter/
converter
unit
Power
supply
U
V
W
R/L1
S/L2
T/L3
M
