| Stephen 2008-03-30, 1:25 pm |
| On 30 Mar, 06:49, Aditya <armun...@gmail.com> wrote:
> Hullo.
>
> I was asked this question during my Lab viva.
>
> " There is a circuit with =A0SCR, without the gating circuit of the SCR
> connected ( Assume it to be isolated so that the firing of the SCR
> wont occur anyway due to it. ) The present Voltage source (V1) is a
> 100V rms sine supply. Presently, the SCR doesnt condect, i.e the SCR
> is OFF. The V1 is disconnected, another Voltage source (V2), 100 V
> rms, sine o/p is connected. The SCR now conducts !!! How ??? "
>
> The answers given by me were
> 1. The new Vsource must have given a step i/p and hence the Voltage
> breakdown ( dv/dt) of the SCR must have occured. ( He shook his head,
> as in NO )
> 2. The temperature must have changed during the process of changin of
> Vsource. ( Again shook his head.)
> 3. The internal resistance of the V2 must be less so that it gives
> somewht higher o/p to cause breakdown of SCR.. ( Again the wrong
> answer he said. )
>
> So, WHat else can it be ?????
Maybe he wants to hear you say that an SCR with a floating gate
behaves as a Shockley diode.
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