Mitsumi electronic FR-F520-0.75K, 55K Other wiring, Power harmonics, Harmonics RF Noise

2.3 Other wiring

INSTALLATION AND WIRING

2.3.1 Power harmonics

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 counter measures.

•The differences between harmonics and RF noise are indicated below:

Item	Harmonics	RF Noise
Frequency	Normally 40th to 50th degrees or less, (up	High frequency (several 10kHz to MHz order)
	to 3kHz or less)
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.

	Power factor
	improving DC
NFB	reactor

Motor

Inverter IM

2

Power factor	Do not insert power factor
improving AC	improving capacitor
reactor

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, since the overcurrent protection is activated by an overcurrent that flows in the inverter, do not insert a capacitor or surge suppressor on the inverter's output when the motor is inverter-driven. To improve the power factor, insert a power factor improving reactor in the inverter’s input or DC circuit. For details, refer to the technical information.

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