Anonymous asked in Science & MathematicsEngineering · 9 years ago

how to apply gate pulse to scr?

i am assigned to construct speed control circuit of DC motor using scr. so, if possible please provide information about how to adjust the firing angle too. thanks in advance.

1 Answer

  • 9 years ago
    Favorite Answer

    You can apply a pulse to gate if cathode is grounded, in several ways. Often this pulse can be applied through a low resistance of say 100 ohms to 330 ohms. the pulse amplitude should be not much higher than 2V. This is in case the SCR is not directly connected to Ac mains.

    So I would suggest you use a 5:1 step down transformer so that 115V becomes about 23V. Then place a lamp in series with SCR and if erverse blocking of SCR is higher than say 40V, connect across the 23V secondary. Choose a transformer with say 1 amp rating for 23V, and place the lamp load such that it is less than 500mA.

    To start with one can experiment with a function geneartor set close to 50hz, and providing a pulse of 2V with pulse width of say 1mS. generally this has to be obatined from the 23V ac sec. output through an appropriate "phase shifter"...

    Do read about this before you attempt all this. Search for

    triggering of SCR_ tutorials

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