Mitsubishi Electronics FR-A500 ユーザーズマニュアル

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Power harmonics may be generated from the converter section of the inverter, affecting power supply

equipment, power capacitors, etc. Power harmonics are different in generation source, frequency and

transmission path from radio frequency (RF) noise and leakage currents. Take the following measures.

•

 The differences between harmonics and RF noise are indicated below:

Frequency

Normally 40th to 50th degrees or less, (up 
to 3kHz or less) 

High frequency (several 10kHz to 1GHz order)

Environment

To wire paths, power impedance

Across spaces, distance, laying paths

Quantitative understanding

Logical computation is possible

Occurs randomly, quantitative understanding is difficult.

Generated amount

Approximately proportional to load capacity

According to current fluctuation rate (larger with faster 
switching)

Immunity of affected device

Specified in standards for each device.

Differs according to maker's device specifications.

Example of safeguard

Install a reactor

Increase the distance.

•

 Safeguard

The harmonic current generated from the inverter to the

power supply differs according to various conditions such as

the wiring impedance, whether a power factor improving

reactor is used or not, and output frequency and output

current on the load side.

For the output frequency and output current, the adequate

method is to obtain them under rated load at the maximum

operating frequency.

Note: A power factor improving capacitor or surge suppressor on the inverter's output may overheat or

be damaged due to the harmonics of the inverter output. Also, when an overcurrent flows in the

inverter, the overcurrent protection is activated. Hence, when the motor is driven by the inverter,

do not install a capacitor or surge suppressor on the inverter's output. To improve the power

factor, insert a power factor improving reactor on the inverter's primary side or in the DC circuit.

For details, refer to the FR-A500/E500 series technical information.

NFB

IM

Inverter

Power  factor
improving DC
reactor

Motor

Do not insert power factor 
improving capacitor

Power factor
improving AC
reactor