Which loads typically cause harmonic distortion and what issues may result?

• A. Linear resistive loads; improved stability
• B. Non-linear loads such as switch-mode power supplies; overheating and reduced power quality
• C. Any load at high voltage; no issues
• D. Only large three-phase motors cause distortion

Answer: (B)

Harmonic distortion happens when the current drawn from the electrical system isn’t a smooth sine wave. Non-linear loads, like switch-mode power supplies, draw current in short pulses or bursts instead of a clean sinusoidal flow. That pulsed current creates harmonic currents, which ride on the voltage waveform and distort both current and voltage shapes.

Because of these harmonics, you can see overheating in transformers and conductors from extra I²R losses, reduced power quality and efficiency, nuisance tripping of breakers, and potential interference with other equipment or protection devices. In short, non-linear loads such as SMPS are the typical culprits, and the resulting distortions lead to the listed issues.

Linear resistive loads don’t distort the waveform and thus don’t cause these problems, and simply operating at high voltage isn’t a guarantee of distortion. Large motors can contribute under certain drive conditions, but the key factor is the non-linear nature of the load, not the size or voltage alone.