Power Supply Harmonics; Installation Of A Reactor - Mitsubishi Electric 800 Series Instruction Manual

3.2

Power supply harmonics

The inverter 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.
• The differences between harmonics and noises
Item
Frequency
Location
Quantitative understanding
Generated amount
Affected equipment immunity
Countermeasure
• Countermeasures
The harmonic current generated from the inverter
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.
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 on the inverter input side or in the DC circuit.
3.3

Installation of a reactor

When the inverter is connected near a large-capacity power transformer (1000 kVA or more) or when a power factor
correction capacitor is to be switched over, an excessive peak current may flow in the power input circuit, damaging the
converter circuit. To prevent this, always install an AC reactor, which is available as an option.
MCCB
Power
supply
Harmonics
Normally 40th to 50th degrees or less (3
kHz or less).
To-electric channel, power impedance.
Theoretical calculation possible.
Nearly proportional to the load capacity.
Specified by standards per equipment.
Provide a reactor.
AC reactor
Inverter
MC
R X
R/L1 U
S Y
S/L2 V
Z
T
T/L3 W
PRECAUTIONS FOR USE OF THE INVERTER
High frequency (several 10 kHz to 1 GHz order).
To-space, distance, wiring path,
Random occurrence, quantitative grasping difficult.
Changes with the current variation ratio. (Gets larger as
switching speed increases.)
Different depending on maker's equipment specifications.
Increase distance.
DC reactor
MCCB MC
R X
S Y
T Z
AC reactor
(kVA)
5300
5000
Capacities requiring
installation of
4000
AC reactor
3000
M
2000
1000
110165 247 330 420
Power supply harmonics
Noise
P/+ P1
R/L1 U
S/L2 V M
T/L3 W
Inverter
Do not install power
factor improving capacitor.
550 kVA
Inverter capacity
3
71