What is an SCR?

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• published: 16 May 2014
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What is an SCR? presented by Katie Rydzewski for Galco TV. Buy the items featured in this video at 800-337-1720 or visit: http://www.galco.com/get/SCRs?source=YouTubeHowTo An SCR is an acronym for silicon-controlled rectifier and is commonly referred to as a thyristor. It is a unidirectional semiconductor similar to a diode, which allows for current to flow in only one direction. It differs from a standard diode by having a third connection called a gate that controls when the SCR turns on. The gate signal is typically a voltage pulse that will turn on the SCR and allow for it to conduct the current. The SCR will continue to stay on as long as it is forward biased and the voltage across it is the proper polarity. To shut off the SCR, the voltage across it has to be reversed. They are typically found on AC circuits where the voltage is constantly switching polarities. In an AC circuit it is possible to control what portion of each half cycle is passed through the SCR by controlling the time of the gate pulse relative to zero crossing. Since current can only flow in one direction, SCRs are also used in rectifying circuits where the AC voltage is converted to DC, such as in a DC drive. These devices are typically used in high power applications. Galco is a Factory Authorized Stocking Distributor for Over 150 Brands of Industrial Electrical & Electronic Automation, Controls and Component Products; On-Site and Send-In Repair Services for Industrial Control & Automation Products for Over 2,000 Brands; Engineered Systems Integration, Retrofits & Upgrades for Variable Speed Drives, CNC, PLC Systems, Dynamometers & Test Stand Applications. Visit us online at http:// www.galco.com or call us at 800-337-1720. http://www.galco.com/safety With respect to the usage, installation or assembly of any products described in this video, Galco Industrial Electronics, Inc., a Michigan corporation, encourages you to follow the requirements and/or guidelines of: i) the Occupational Safety and Health Act of 1970, Public Law 91-596, as amended, and all laws, rules and regulations implemented in relation thereto; ii) the National Electric Code®; and iii) NFPA 70E®. Any installation, assembly or work described in this video should be performed by a qualified licensed electrician. GTV, Galco, galco.com, Galco Industrial Electronics, and Galco Industrial Electronics, Inc. are registered and/or pending registered trademarks under the U.S. Patent and Trademark Office, assumed names, registered domain names, and/or trade names of Galco Industrial Electronics, Inc., a Michigan corporation. LEGAL DISCLAIMER: While we have made every attempt to ensure that the information provided is accurate and has been obtained from reliable sources, Galco is not responsible for any errors or omissions, or for the results obtained from the use of this information. All information is provided "as is", with no guarantee of completeness, accuracy, timeliness or of the results obtained from the use of this information, and without warranty of any kind, express or implied, including, but not limited to warrantees of performance, merchantability and fitness for a particular purpose. At all times you should defer to the instructions and safety guidelines issued by the manufacturer. In no event will Galco, its agents or employees thereof be liable to you or anyone else for any decision made or action taken in reliance on the information provided to you or for any consequential, special or similar damages, even if advised of the possibility of such damages.