Electro-Voice 1252, 250 operation manual Distorted Current Wave

Total A Phase Current with Harmonics

1500
1000
500
0
-500	1	33	65
-1000
-1500

Figure 1.11: Distorted Current Wave

The distortion observed in Figure 1.11 can be modeled as the sum of several sinusoidal waveforms of frequencies that are multiples of the fundamental 60 Hz frequency. This modeling is performed by mathematically disassembling the distorted waveform into a collection of higher frequency waveforms. These higher frequency waveforms are referred to as harmonics. Figure 1.12 shows the content of the harmonic frequencies that make up the distortion portion of the waveform in Figure 1.11.

							Expanded Harmonic Currents
	250
	200
	150
	100
Amps	50
	0	1	3	5	7	9
	-50						11	13	51	17	19	21	23	25	27	92	31	33	35	37	39
	-100
	-150
	-200
	-250
			2 Harmonic Current							3 Harmonic Current						5 Harmonic Current
			7 Harmonic Current							A Current Total Hrm

Figure 1.12: Waveforms of the Harmonics

The waveforms shown in Figure 1.12 are not smoothed but do provide an indication of the impact of combining multiple harmonic frequencies together.

When harmonics are present it is important to remember that these quantities are operating at higher frequencies. Therefore, they do not always respond in the same manner as 60 Hz values.

Electro Industries/GaugeTech Doc # E107706 V1.25 1-11