EMC and leakage currents
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 differences between harmonics and noises are indicated below:
Affected equipment immunity
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 they should be calculated in the
conditions under the rated load at the maximum
The power factor improving capacitor and surge suppressor on the inverter output side may be overheated or damaged by the
high frequency 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.
Normally number 40 to 50 max.
(3kHz or less)
To-electric channel, power impedance
Theoretical calculation possible
Nearly proportional to load capacity
Specified in standard per equipment
High frequency (several 10kHz to 1GHz order)
To-space, distance, wiring path
Random occurrence, quantitative grasping difficult
Depending on the current fluctuation ratio (larger as
switching is faster)
Different depending on maker's equipment
Do not insert power
factor improving capacitor.