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A thyristor (/ θ aɪ ˈ r ɪ s t ər /, from a combination of Greek language θύρα, meaning "door" or "valve", and transistor [1]) is a solid-state semiconductor device which can be thought of as being a highly robust and switchable diode, allowing the passage of current in one direction but not the other, often under control of a gate electrode, that is used in high power applications ...
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 ...
Thyristors are switched on by a gate signal, but even after the gate signal is de-asserted (removed, reverse biased), the thyristor remains in the on state until a turn-off condition occurs (which can be the application of a reverse voltage to the terminals or a decrease of the forward current below a certain threshold value known as the ...
The current in the TCR is varied from maximum (determined by the connection voltage and the inductance of the reactor) to almost zero by varying the "Firing Delay Angle", α. α is defined as the delay angle from the point at which the voltage becomes positive to the point at which the thyristor valve is turned on and current starts to flow.
In thyristor-based converters, many thyristors are connected in series to form a thyristor valve, and each converter normally consists of six or twelve thyristor valves. The thyristor valves are usually grouped in pairs or groups of four and can stand on insulators on the floor or hang from insulators from the ceiling.
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The wafer device is similar to a gate turn-off thyristor (GTO). They can be turned on and off by a gate signal, and withstand higher rates of voltage rise (dv/dt), such that no snubber is required for most applications. The structure of an IGCT is very similar to a GTO thyristor. In an IGCT, the gate turn-off current is greater than the anode ...
The thyristor power controller switches 60% of the solid waves to the load while blocking 40%. The operating mode is to be regarded as unproblematic. Only in the case of a too weakly designed network, it is possible for illuminating installations which are connected to the same network to have undesired luminance fluctuations (flicker effect).