A semiconductor controlled rectifier or silicon controlled rectifier is a solid-state current-controlling four-layer device. In 1956 Moll, Tanenbaum, Goldey and Holonyak of Bell Laboratories was developed the principle of four-layer p–n–p–n switching.
In January 1958 Dr Ian M. Mackintosh of Bell Laboratories was presented the practical demonstration of silicon controlled switching and detailed theoretical behavior of a device in agreement with the experimental results. The name “silicon controlled rectifier” is General Electric’s trade name for a type of thyristor. A team of power engineers led by Gordon Hall was developed The SCR and in 1957 Frank W.BillnGutzwiller commercialized.
Some sources define thyristors and silicon-controlled rectifier as synonymous, other sources define silicon-controlled rectifiers as a proper subset of the set of thyristors, those being devices with at least four layers of alternating n- and p-type material. According to Bill Gutzwiller,and “thyristor” was applied later, the terms “SCR” and “controlled rectifier” were earlier, as usage of the device spread internationally.
As opposed to TRIACs, SCRs are unidirectional devices (i.e. can conduct current only in one direction) TRIAC which are bidirectional (i.e. current can flow through them in either direction). SCRs can be triggered normally only by currents going into the gate as opposed to TRIACs, which can be triggered normally by either negative or a positive current applied to its gate electrode.Where the control of high powerSCRs is mainly used in devices, possibly coupled with high voltage, is demanded. Their operation makes them suitable for use in high-voltage to medium AC power control applications, such as lamp dimming, power regulators and motor control.
SCRs and similar devices are used for rectification of high-power AC in high-voltage dc power transmission. They are also used in the control of welding machines, mainly GTAW (gas tungsten arc welding) processes similar. It is used as switch in various devices.
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In January 1958 Dr Ian M. Mackintosh of Bell Laboratories was presented the practical demonstration of silicon controlled switching and detailed theoretical behavior of a device in agreement with the experimental results. The name “silicon controlled rectifier” is General Electric’s trade name for a type of thyristor. A team of power engineers led by Gordon Hall was developed The SCR and in 1957 Frank W.BillnGutzwiller commercialized.