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Electrical Riddle No.50 - Lamps flicker(visual comfort)
If we connect an incandescent or CFL or vapour lamp(FL/Hg/Na/MH) via a diode will there be flicker and will the power consumption be halved?
Author : Sinnadurai Sripadmanaban - From: Srilanka
Mon, February 7th, 2011 - 18:04
Regarding following figure, the input has a time average of 0, and root mean square (RMS) value equal to Vpeak/√2, where Vpeak is the maximum value of Vac. The output has a nonzero average value given by: Vdc= Vpeak /π and an RMS value equal to Vpeak/2 which related to lamp output.
Therefore the (RMS) value of incandescent lamp current will be 1/√2 times and power consumptions (Ri2) in circuit with diode will be 1/2 times. Also because stability of circuit frequency we don't face to any flickers generally. However, subharmonic frequency components may be generated that are undesirable as they may set up subharmonic resonance in the power supply system, cause lamp flicker.
Author : Hamid - From: Iran- Firouzabad in Fars
Wed, February 9th, 2011 - 18:12
Has anybody tried it?. What will be the output for other types of lamps?. 
Author : Sinnadurai Sripadmanaban - From: Srilankan
Thu, February 10th, 2011 - 13:30
Equivalent circuit of vapor lamp which typically equipped with ballast is series RL, therefore there are not any importance difference between two circuit analysis. Meanwhile note to following additional information about flicker and effects of voltage quality to its amount.
Flicker can be separated into two types: cyclic and noncyclic. Cyclic flicker is a result of periodic voltage fluctuations on the system, while noncyclic is a result of occasional voltage fluctuations.
An example of sinusoidal-cyclic flicker is shown in Figure below. This type of flicker is simply amplitude modulation where the main signal (60 Hz for North America) is the carrier signal and flicker is the modulating signal. Flicker signals are usually specified as a percentage of the normal operating voltage. By using a percentage, the flicker signal is independent of peak, peak-to-peak, rms, line-to-neutral, etc.
Typically, percent voltage modulation is expressed by

The frequency content of flicker is extremely important in determining whether or not flicker levels are observable (or objectionable).
Describing the frequency content of the flicker signal in terms of modulation would mean that the flicker frequency is essentially the frequency of the modulating signal. The typical frequency range of observable flicker is from 0.5 to 30.0 Hz, with observable magnitudes starting at less than 1.0 percent.
The human eye is more sensitive to luminance fluctuations in the 5- to 10-Hz range. As the frequency of flicker increases or decreases away from this range, the human eye generally becomes more tolerable of fluctuations.
One issue that was not considered in the development of the traditional flicker curve is that of multiple flicker signals. Generally, most flicker-producing loads contain multiple flicker signals (of varying magnitudes and frequencies), thus making it very difficult to accurately quantify flicker using flicker curves.
Author : Hamid - From: Iran- Firouzabad in Fars
Thu, February 10th, 2011 - 19:14
For incandescent or other types will the lumen output and brightness  become half?. Will the lamp life be affected?. 
Author : Sinnadurai Sripadmanaban - From: Srilanka
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