What is Scr: Definition and 24 Discussions

The SCR-270 (Set Complete Radio model 270) was one of the first operational early-warning radars. It was the U.S. Army's primary long-distance radar throughout World War II and was deployed around the world. Its also known as the Pearl Harbor Radar, since it was an SCR-270 set that detected the incoming raid about 45 minutes before the December 7, 1941, attack on Pearl Harbor commenced.
Two versions were produced, the mobile SCR-270, and the fixed SCR-271 which used the same electronics but used an antenna with somewhat greater resolution. An upgraded version, the SCR-289, was also produced, but saw little use. The -270 versions were eventually replaced by newer microwave units based on cavity magnetron that was introduced to the US during the Tizard Mission. The only early warning system of the sort to see action in World War II was the AN/CPS-1, which was available in mid-1944, in time for D-day.

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  1. Javier Lopez

    High Power SCR Driver Design for Plasma Compression Coil Activation

    I have made following design to drive two high power hokeypuck SCRs to activate a Plasma compression coil. As long as catode falls below 0V, I do not know if it is needed to insert diodes from the optoisolated driver A1 (and A2) and the limiting current resistor R1 (and R2):
  2. J

    Average current in single phase bridge converter SCR

    << Mentor Note -- thread moved from the technical forums, so no Homework Template is shown >> I'm studying controlled rectifiers and for full wave bridge rectifiers the notes(that I'm studying from says) It says that the average load current is Id / 2 I don't understand how. Why should the 2...
  3. J

    Troubleshooting 1/8 HP Motor w/ SCR & Relays

    I am using an 1/8 HP motor with an SCR type dc drive and 1/4hp AC single phase control relays. I keep having a problem with welded relay contacts. Should I go to 1H/P relays? I don't know why I would have to being the HP of the motor is lower that the relay?
  4. F

    How does a SCR controls the speed of motor

    can you do it by increasing the series resistance?
  5. U

    How to quantify relatively simple experimental errors

    Homework Statement For my coursework task, i am to quantify and discuss errors associated with an experimental procedure. This involved a thyristor control unit which allowed the firing angle of two thyristors (in a half controlled bridge rectifier) to be varied with a rotary dial or pot/rheo...
  6. G

    Can anyone explain me this circuit

    http://prntscr.com/60xcwx Thank you
  7. B

    Conduction Angle in SCR Single Phase Rectifiers

    Hi all, When considering a half wave SCR rectifier (single phase) with an RL load, the term θ (conductive angle) appears in equations relating to the performance of the circuit. In terms what is physically happening in the circuit, what does θ actually represent?
  8. P

    SSR vs SCR for heating element : what is the difference?

    Hello, I have Silicon Carbide heating elements which should be used with a Step Down Transformer or SCR as mentioned in the guide from manufacturer. I currently have a SSR available at hand, and was hoping it could be used instead. The Solid State Relay when connected to PID can...
  9. A

    Operation of SCR: Starting Conduction & J2 Breakdown

    When we apply voltage to the gate of an SCR, how does it start conducting? Current passes through gate to cathode. Then how the breakdown of junction j2 occurs?
  10. E

    Doubt on snubber circuit for an scr for dv/dt protection

    The main aim of turning on/off an scr is to disconnect source from load. I read in dv/dt protection of scr using snubber circuit, the scr may turn on when dV/dt is very high as the charging current i=cdV/dt will be high enough to turn on scr. So we are using a snubber circuit to divert this high...
  11. D

    Can an SCR handle high voltage?

    I'm looking on digikey for an SCR and there is a parameter that concerns me: Voltage - On State (Vtm) (Max) It seems the maximum voltage rating for this parameter is 3.7V. I must be misunderstanding what this parameter means. Is there somewhere I could look up what it means? I plan to run a...
  12. Femme_physics

    Engineering Basic SCR circuit - drawing graphs

    Homework Statement http://img444.imageshack.us/img444/3062/firing.jpg (in Hebrew it says "circuit to regulate firing angle") 1) Note the main difference between SCR and TRIAC. 2) The following is a circuit to regulate the load RL, regulated by SCR. The SCR is fired at an angle of 90 degrees...
  13. Femme_physics

    Calculating time when SCR starts up

    Homework Statement Given a circuit to control the volume of an electric bell P. Potentiometer T is set to 600K ohms. The breakout voltage of the SCR (at the SCR gate) is 20 micro-amperes. And the max gate that will start up the SCR is 0.7 Volts...
  14. P

    Why does the SCR remain 'ON' even though the gate pulse is removed?

    Why does the SCR remain 'ON' even though the gate pulse is removed? I understood the two transistor model but I want to know the bare physics of it. If you remove the gate pulse only the +ve anode w.r.t. cathode remains, thereby making junction J2 reverse biased hence current should fall of...
  15. Femme_physics

    Engineering Circuit to control a full wave via single SCR

    Homework Statement http://img543.imageshack.us/img543/7906/ddd2e.jpg To translate from Hebrew from left to right: Net Voltage 220 Vac, Pull Down Transformer, full wave rectifier (marked with a, b, c, d), below it is a "load" (or resistance), and to the right it says "a circuit to control the...
  16. O

    SCR and Diode are Active or Passive Components?

    Hello! SCR and Diode are Active or Passive Components? Please clarify the definition of Active and passive components. I have some confusion in it! Regards otoman
  17. A

    Creating a Coilgun Project Using a Puck-Style SCR

    I have a puck-style SCR with a cathode, anode and gate. I'm planning on using it to dump two series capacitors (450v + 450v) into a coil for a "coilgun" project. I understand that the SCR is triggered when a circuit is completed through the gate and anode using, for example, a battery and a...
  18. L

    SCR as a switch control for automatic light dimmer

    Hi guys, can u guys help me on this?? I want to design and construct an automatic light dimmer circuit that controls the energy delivered to a 12V or 24V DC light bulb corresponding to the ambient light intensity. The control of energy will be established through switching action to improve...
  19. L

    Automatic light dimmer using SCR as switch control

    Hi guys, can u guys help me on this?? I want to design and construct an automatic light dimmer circuit that controls the energy delivered to a 12V or 24V DC light bulb corresponding to the ambient light intensity. The control of energy will be established through switching action to improve...
  20. V

    What Will Happen When an SCR Is Heated?

    what will happen when a SCR is heated.will it turn on the SCR at a value much lower than breakdown voltage?
  21. T

    Solving SCR Circuit Problem - EE Student Seeking Help

    I came across a circuit online to vary the 220V input into a welder. This is done to control the amount of current entering the piece being welded, using a foot pedal. The circuit has worked for many people. I built the circuit, but it doesn't work. R2 blew when I would crank the pot up, and...
  22. T

    Devising a Circuit with SCR Controlled by Agilent Vee

    This really isn't a homework problem, but it is somewhat. Please move it if you see fit. I need to devise a circuit with an scr in it, to be controlled using Agilent Vee. Unfortunatley my teacher isn't the best, and I am not completely sure on the properties of SCR's. I understand that...
  23. W

    Control SCR w/ Microprocessor & Opto Coupler

    How can we control an SCR through a microprocessor with an opto coupler used as an 'isolating and amplification' device between the microprocessor and the SCR.
  24. D

    SCR Propulsion Systems: Electric Motor & Towboat Power

    Anybody know anything about SCR...can an electric motor power a towboat with batteries and back up generator power say 1800 hp.
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