WHAT TYPES OF LOADS CAUSE HARMONIC CURRENTS?
Let’s understand the difference between linear and nonlinear loads. A linear load is a load that opposes the applied voltage with constant impedance resulting in a current waveform that changes in direct proportion to the change in the applied voltage. Examples of these loads are resistance heating, incandescent lighting, motors, etc. If the impedance is constant, then the applied voltage is sinusoidal, and the current waveform will also be sinusoidal. A nonlinear load, on the other hand, is a load that does not oppose the applied voltage with constant impedance. The result is a nonsinusoidal current waveform that does not conform to the waveform of the applied voltage. Nonlinear loads have high impedance during part of the voltage waveform, and when the voltage is at or near the peak the impedance is suddenly reduced. The reduced impedance at the peak voltage results in a large, sudden, rise in current flow until the impedance is suddenly increased resulting in a sudden drop in curren
