Mitsubishi Electronics FR-S500 instruction manual Power supply harmonics

Main circuit terminals

1.2.10 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 following table indicates differences between harmonics and noise:

Item		Harmonics					Noise
Frequency	Normally 40th to 50th degrees or less					High frequency (several 10kHz
	(up to 3kHz or less)					to 1GHz order)
Environment	To-electric channel, power impedance					To-space, distance, wiring path
Quantitative	Theoretical calculation possible					Random occurrence,
understanding						quantitative grasping difficult
Generated amount	Nearly proportional to load capacity					Change with current variation
						ratio (larger as switching speed
						increases)
Affected equipment	Specified in standard per equipment					Different depending on maker's
immunity						equipment specifications
Suppression example	Provide reactor.					Increase distance.
Suppression technique				FR-BEL
Harmonic currents produced			FR-BAL
on the power supply side by		NFB
the inverter change with such								Motor
conditions as whether there					Inverter
power factor improving reactor
are wiring impedances and a									IM
(FR-BEL(-H) or FR-BAL(-H))
and the magnitudes of output						Do not provide power factor
frequency and output current
on the load side.						improving capacitor.

For the output frequency and output current, we understand that they should be calculated in the conditions under the rated load at the maximum operating frequency.

CAUTION

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. To improve the power factor, insert a power factor improving reactor on the inverter's primary side or DC circuit. For full information, refer to page 17.

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