Pulsation of luminous flux is one of the characteristics of artificial lighting, indicating the frequency of light flicker. A quantitative characteristic of pulsation is the pulsation factor (Kp, %), equal to the ratio of half the difference between the maximum and minimum illuminance for the period in Lux to the average illuminance for the same period:
According to the sanitary standards and regulations, Kp values in the range from 5 to 20% are acceptable.
LED luminaires operate with both AC and DC power. There is no pulsation in DC operation. When operating on AC power, pulsation can be minimized by using a driver that converts AC current to DC current. The driver is part of any LED luminaire. However, only a driver can minimize pulsation quality driver – Otherwise, it will not be very different from the pulsation of a fluorescent luminaire with an old ECG.
The effect of pulsation on human health
The human eye practically does not distinguish the pulsation of the light stream - the brain does not have time to fully process the visual information, varying with a frequency of more than a few tens of Hertz. This property of vision is the basis of video images, where the frames change with a frequency of 25 Hz or more, and the viewer perceives what he sees as a single picture, smoothly changing over time.
Nevertheless, according to medical research data, the human brain registers changes of information coming through the visual organs up to 300 Hz. Such changes of visual information are not perceived on the conscious level, but have a significant impact of non-visual nature, and this impact is quite negative: the "victim" feels unexplainable discomfort, fatigue, dizziness even in seemingly comfortable and bright rooms. Systematic non-visual exposure to light (for example, in the workplace) can serve as an indirect cause of permanent depression, insomnia, cardiovascular diseases and cancer.
Pulsation of light flux above 300 Hz is considered safe for human health. In any case, so far no effect on human health and well-being has been observed.
Speaking of the effects of pulsating light on human health and safety, it is impossible not to mention such a phenomenon as the stroboscopic effect. The stroboscopic effect occurs when the flicker frequency of the luminaire is a multiple of or coincides with the frequency of movement of parts of the working equipment, so that they seem to move slowly in the opposite direction or not moving at all. For example, the rotating shaft of a milling machine, a circular saw running, the blade assembly of a meat cutter, etc. may seem stationary. The noise of one mechanism will naturally not be heard in the overall production hum. As a result, tens of thousands of workers lose their limbs (and sometimes their lives) every year. The stroboscopic effect is often the "culprit" in the investigation of industrial accidents. The stroboscopic effect can occur at a pulsation factor of 10%.
In general, despite the fact that sanitary standards allow the depth of pulsation up to 20% (for some rooms - up to 10-15%), the optimal for human comfort and safety was recognized pulsation, whose coefficient does not exceed 4-5%. Only LED luminaires are able to provide such indicators with a quality driver.
Pulsation and sanitary standards
The permissible level of pulsation for different institutions are specified in the following normative documents: (Construction Norms and Rules) (Sanitary Rules and Norms).
According to the norms, the pulsation factor on the working surface of the workplace should not exceed 10-20% (depending on the specifics of the room and the accuracy of the work performed), and in rooms equipped with computers - 5%. In general education as well as in pre-school institutions the pulsation depth should not exceed 10%.
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