Mitsubishi Electric FR-A820-00046 (0.4K), Instruction Manual

Page: 155 / 1218

Precautions for use of the inverter Power supply harmonics
FR-A800 3 - 11
3.2 Power supply harmonics
3.2.1 Power supply harmonics
The inverter may generate power supply harmonics from its converter circuit to affect the power gen-
erator, 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 countermeas-
ure suppression techniques.
The differences between harmonics and noises
Countermeasures
The harmonic current generated from the inverter to the input side differs according to various con-
ditions such as the wiring impedance, whether a reactor is used or not, and output frequency and out-
put current on the load side.
For the output frequency and output current, we understand that this should be calculated in the con-
ditions under the rated load at the maximum operating frequency.
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.
Tab. 3-6: Differences between harmonics and noises
I002421E
Fig. 3-9: Reduction of power supply harmonics
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 exces-
sive 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 on the inverter input side or in the DC circuit.
R
S
T Z
Y
X
U
V
W
P1
R/L1
S/L2
T/L3
P/+
Po
w
e
r s
u
p
p
ly
AC reactor
(FR-HAL)
DC reactor
(FR-HEL)
M
3~
Inverter
Do not insert power
factor improving capacitor
MCCB MC