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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 ...
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.
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).
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.
TRIACs are a subset of thyristors (analogous to a relay in that a small voltage and current can control a much larger voltage and current) and are related to silicon controlled rectifiers (SCRs). TRIACs differ from SCRs in that they allow current flow in both directions, whereas an SCR can only conduct current in a single direction.
An MOS-controlled thyristor (MCT) is a voltage-controlled fully controllable thyristor, controlled by MOSFETs (metal–oxide–semiconductor field-effect transistors). It was invented by V.A.K. Temple in 1984, and was principally similar to the earlier insulated-gate bipolar transistor (IGBT). [ 1 ]
Typically, an SVC comprises one or more banks of fixed or switched shunt capacitors or reactors, of which at least one bank is switched by thyristors. Elements which may be used to make an SVC typically include: Thyristor-controlled reactor (TCR), where the reactor may be air- or iron-cored; Thyristor-switched capacitor (TSC) Harmonic filter(s)