In a lamp ballast, the crest factor is the ratio of the maximum lamp current relative to the average operating current.
Crest factor is a parameter of a waveform, such as alternating current or sound, showing the ratio of peak values to the effective value. In other words, the crest factor indicates how extreme the peaks are in a waveform. Crest factor 1 indicates no peaks, such as direct current or a square wave. Higher crest factors indicate peaks, for example, sound waves tend to have high crest factors.