|
Home > Archive > Electrical Engineering > March 2008 > Thyristor ON !?!
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
|
|
| Aditya 2008-03-30, 3:25 am |
| Hullo.
I was asked this question during my Lab viva.
" There is a circuit with SCR, 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 ?????
| |
| Palindrome 2008-03-30, 9:25 am |
| Aditya wrote:
> Hullo.
>
> I was asked this question during my Lab viva.
>
>
> " There is a circuit with SCR, 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 ?????
What it *is* is a stupid question, with an almost unlimited number of
potential ( ;) answers.
What's the frequency of the second voltage source? Is it superimposed on
another voltage? Is the circuit next to a radar dish and the transmitter
has started up? etc, etc, etc.
Engineers use the application(s) and environment(s) to construct
paradigms by which to produce solutions to problems. Give them an
infinite number of both and they will come up with an infinite number of
solutions. Was the teacher ex-army?
--
Sue
|
|
|
|
|