Flicker, Transients and Noise
Repetitive voltage reductions in lighting circuits can be detected by the human eye, a phenomena known as “flicker.” The term flicker refers to a very specific problem related to human perception of light produced by incandescent light bulbs, not necessarily general voltage fluctuations.
Some common sources of flicker include: Arc welders, Electric boilers, Industrial motors, Lasers, Photocopying machines, Saw mills, and X-ray machines.
Fig1. Flicker, transients, and noise examples
Transients occur when spikes are superimposed on a voltage or current sine wave, ranging in amplitude from just a few volts to several thousand volts. Lighting and utility switching typically cause high energy impulsive transients of short duration, while electronic devices, VFDs and switching inductive loads typically cause low energy transients continuously.
- Impulsive Transients last anywhere from 50 nanoseconds to >1 milliseconds
- Oscillatory transients last anywhere from 0.3 milliseconds to 5 microseconds
Noise refers to unwanted, high frequency oscillations that are superimposed on an alternating voltage or current sine wave. This phenomena is usually intensified by improper grounding and is capable of disrupting electronic devices such as computers and programmable controllers.