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A-12
App.B Suppressing Harmonics for General-purpose
Inverters
- Disclaimer: This document provides you with a summary of the Technical Document of the Japan
Electrical Manufacturers' Association (JEMA) (February 2000). It is intended to apply to the domestic
market only. It is only for reference for the foreign market. -
Preface
Recently, electric devices and appliances based on the electronic technology are rapidly diffusing
through industries and establishing their positions that give solutions to the demands for less-human
power and factory automation. Contrarily, this diffusion causes hazards to other electric equipment due
to the harmonic current that electronic appliances generate and diffuse onto the commercial power
lines. Such kinds of hazards have been increasing year by year. Under such circumstance, the Ministry
of International Trade and Industry enacted "Japanese guideline for suppressing harmonics in home
electric and general-purpose appliances" in September 1994.
According to the guideline, the Japan Electrical Manufacturers' Association (JEMA) has established
the technical document for suppressing harmonics for the general-purpose inverter which is one
equipment regulated by the guideline, and has applied it on January 1, 1997. The guideline, however,
is updated and applied on September 24, 1997. To follow the update, the Japan Electrical
Manufacturer's Association has updated this document.
This booklet guides you to an outline of the new guideline, the principle of mechanism generating
harmonic current in the inverter and the countermeasures against it. We at JEMA hope you understand
the guideline, cooperate with it and promote actions for suppressing harmonics.
B.1
Harmonics and Influence
[ 1 ] Harmonics
A sinusoidal wave on the commercial power source supplied by an electric power company is called
a fundamental wave. A harmonic refers to a sinusoidal component of a periodic wave having a
frequency that is an integral multiple of the fundamental frequency. If superimposed with the
harmonic, the fundamental wave will be distorted as shown in Figure B.1.
If an input circuit of equipment is equipped with a rectifier circuit and a filtering circuit including a
reactor or capacitor, then the waveform of input current will be distorted. This phenomenon is the
main factor that generates harmonics.
Refer to A.2 [1] "Inverter noise" for details of the principle of inverter operation.
Figure B.1 Fundamental and Harmonic Components
[ 2 ] Influence
Harmonics generated by the equipment may propagate on the power line and influence other systems
or equipment as follows:
(1) Abnormal noise, vibration or burning out caused by harmonic current flowing into the
equipment
(2) Malfunctioning by harmonic voltage applied to the equipment