1972 - oil embargo forced U.S. to become more energy efficient Equipment was designed to operate using short pulses of current instead of continuous current (the method of becoming more efficient). Examples include: Variable speed frequency drives, HID lighting, dimmer switches, computers, TV's, and most other modern electronic devices are energy efficient
Prior to 1972, most electrical loads were linear; that is, they operated on normal utility supplied 60-hertz sine waves.
Linear loads include devices such as motors and incandescent light bulbs With linear loads, higher voltage potential means higher current draw, and vice versa.
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Non-linear loads utilize short pulses of current Therefore, load current is not proportional to the voltage applied When load current and voltage are not proportional entities, harmonics are generated and flow on the power distribution lines.
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" A harmonic is a frequency that is an integer (whole number) multiple (second, third, fourth, fifth, etc.) of the fundamental frequency. The fundamental frequency on power distribution lines is 60 Hz (cycles per second) and changes from the positive alternation to the negative alternation 60 cycles per second. For example, the second harmonic on a 60 Hz power distribution line is 120 (60x2) Hz. The second harmonic waveform completes two cycles during one cycle of the fundamental waveform over the same period of time. The third harmonic is 180 (60 x 3) Hz. The third harmonic waveform completes three cycles during one cycle of the fundamental waveform over the same period of time." (Mazur, 6) (See figure 4)
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A transient, as defined by IEEE Std. 1100-1992, is a subcycle disturbance in the AC waveform that is evidenced by a sharp but brief discontinuity in the waveform. May be of either polarity and may be additive to or subtractive from the nominal waveform.
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Cause electric meters to read inaccurately along with heat
Cause motors and transformers to burn out
Cause neutral wires in a system to overheat, resulting in a multitude of problems
Cause electronic equipment to fail
What Do Harmonics and High Frequency Transient Events Do?