Firing Angle 0-180 Thyristor with UJT

Thread Starter

feisaladam

Joined Nov 18, 2020
10
it works, but i don't know this is correct 0-180 or not because i tried another one 0-90 angle but it looks same, i don't know the difference between them
 

ericgibbs

Joined Jan 29, 2010
13,585
hi,
As you know180 degrees is the complete positive half of the mains cycle.
Try adjusting R1 on the sim until all of the 180 deg is controllable
Lets know what you see.
E
 

ericgibbs

Joined Jan 29, 2010
13,585
hi f,
Thats what I would expect.
Consider that the top of R1 is connected to the half wave rectified voltage of the mains.
So the voltage on R1 increases from 0deg degrees to 90 deg, after that the voltage falls, so the UJT never has sufficient voltage to trigger on the falling 90 deg to 180 deg voltage.

E
Check the UJT Gate voltage waveform on your simulation.
 

Thread Starter

feisaladam

Joined Nov 18, 2020
10
Hi D,
yes, i get both cycles of the mains but it's only for the V gate of the UJT. the thyristor triggering point still can't go beyond 90 deg
 

ericgibbs

Joined Jan 29, 2010
13,585
hi f,
How complex a circuit are you prepared to build, it can be done but it will not be simple.
How you heard of zero crossing detection of the mains cycle.?
E
 

Thread Starter

feisaladam

Joined Nov 18, 2020
10
noo sir, it's actually i'm doing my practicum module and i'm just curious because all of my friend have the same problem and we're just stuck don't know what to do to find the trigger 90-180 deg
 
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