App-31
IM 253710-01E
Appendix
App
Appendix 7 Power Basics (Power/Harmonics/Three Constants Related to the AC Circuit)
Interference caused by harmonic signals
Harmonic signals adversely affect electric devices and facilities. The following are
some examples.
• Phase advance capacitor or series reactor
The reduction of circuit impedance caused by the harmonic current causes
excessive current to flow resulting in vibration, humming, overheating, and
burnouts.
• Cable
Overheating of the neutral conductor caused by harmonic currents flowing through
it in a three-phase four-wire system.
• Potential transformer
Causes magnetostrictive noise of the iron core which leads to increased iron and
copper losses.
• Breaker and fuse
Erroneous operation caused by excessive harmonic current. Causes fuse to blow.
• Communication
Causes noise voltage from electro-magnetic induction.
• Control device
Erroneous operation caused by distorted control signals.
• Audio-visual equipment
Deterioration of performance and life span. Flicker caused by video noise.
Malfunction of parts.