Harmonic voltages and
currents in a Power System are a result of non-linear electric loads.

In a normal AC Power System,
the current varies sinusoidally at a specific frequency, usually 50 or 60
Hertz. When a linear electrical load is connected to the system, it draws a
sinusoidal current at the same frequency as the voltage, though usually not in
phase with the voltage.

Current harmonics are caused
by non-linear loads. When a non-linear load, such as a rectifier / inverter, is
connected to the system, it draws a current that is not necessarily sinusoidal.
The current waveform can become quite complex, depending on the type of load
and its interaction with other components of the system. Regardless of how
complex the current waveform becomes, as described through Fourier Series
analysis, it is possible to decompose it into a series of simple sinusoids,
which start at the power system fundamental frequency and occur at integer
multiples of the fundamental frequency.

Further examples of
non-linear loads include common office equipment such as computers and
printers, Fluorescent lighting, battery chargers, electronic ballasts, variable
frequency drives, and switching mode power supplies.

Total Harmonic Distortion or
THD is a common measurement of the level of harmonic distortion present in
power systems. THD is defined as the ratio of total harmonics to the value at
fundamental frequency.

where Vn is the RMS voltage
of nth harmonic and n = 1 is the fundamental frequency.

**Effects of Harmonics:**

One of the major effects of
power system harmonics is to increase the current in the system. This is
particularly the case for the third harmonic, which causes a sharp increase in
the zero sequence current, and therefore increases the current in the neutral
conductor.

Electric motors experience
losses due to hysteresis and losses due to eddy currents set up in the iron core
of the motor. These are proportional to the frequency of the current. Since the
harmonics are at higher frequencies, they produce higher core losses in a motor
than the power frequency would. This results in increased heating of the motor
core, which (if excessive) can shorten the life of the motor.

The 5th harmonic
causes a Counter Electromotive Force in large motors which acts in the opposite
direction of rotation. The Counter Electromotive Force is not large enough to
counteract the rotation; however it does play a small role in the resulting
rotating speed of the motor.

**Thank you!**

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PREGUNTA EN UNA RESIDENCIA DE 5000 WATTS SERIA NORMAL CONTAR CON UNA TERCERA ARMONICA

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