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Phase-fired control (PFC), also called phase cutting or phase-angle control, is a method for power limiting, applied to AC voltages. [1] It works by modulating a thyristor , SCR , triac , thyratron , or other such gated diode -like devices into and out of conduction at a predetermined phase angle of the applied waveform.
A Voltage controller thyristor based dimmer rack An electrical schematic for a typical SCR-based light dimmer. A voltage controller, also called an AC voltage controller or AC regulator is an electronic module based on either thyristors, triodes for alternating current, silicon-controlled rectifiers or insulated-gate bipolar transistors, which converts a fixed voltage, fixed frequency ...
Solid-state, or semiconductor, dimmers were introduced to solve some of these problems. Semiconductor dimmers switch on at an adjustable time (phase angle) after the start of each alternating-current half-cycle, thereby altering the voltage waveform applied to lamps and so changing its RMS effective value. Because they switch instead of ...
The term brownout comes from the dimming experienced by incandescent lighting when the voltage sags. Brownouts can cause poor performance of equipment or even incorrect operation. A blackout is the total loss of power to a wider area and of long duration. [1] It is the most severe form of power outage that can occur.
In a cathode-ray tube television, the reduced output voltage will make the screen image smaller, dimmer and fuzzier. A linear DC regulated supply will maintain the output voltage unless the brownout is severe and the input voltage drops below the drop out voltage for the regulator, at which point the output voltage will fall and high levels of ...
Dimming fluorescent ballasts and dimming LED drivers often use 0–10 V control signals to control dimming functions. In many cases, the dimming range of the power supply or ballast is limited. If the light output can only be dimmed from 100% down to 10%, there must be a switch or relay available to kill power to the system and turn the light ...
Imbalance between the phases causes problems such as heating in motors and existing wiring, leading to wasteful energy consumption. [7] Some voltage optimisation devices are able to improve balance on the building's electrical supply, reducing losses and improving the longevity of three phase induction motors.
For a two dimensional phase retrieval problem, there is a degeneracy of solutions as () and its conjugate () have the same Fourier modulus. This leads to "image twinning" in which the phase retrieval algorithm stagnates producing an image with features of both the object and its conjugate. [3]