Contents Chapter 1: Introduction 2: Simple Diode Circuits 3: Simple SCR Circuits 4: Fully Controlled 1 PH 5: Fully Controlled 3 PH 6: Semi - Controlled Rectifier Circuits 7: Switch MOde PowerSupply previous page Section Contents next page

 

Chapter 3
Simple SCR Circuits

Section 2
A Single SCR Circuit with a Free Wheeling Diode

 

 

Simulation

The operation of the circuit can be simulated as shown below. During 0 < q < p , the expression for current is:

i(q) = A * exp [ -(q - a)/t) + (E/Z)*sin (q - b ),

where t = wL/R, b = atan (t), Z2 = R2 + (wL)2 = R2*(1 + t2 and a is the firing angle.

During p < q < (2p + a), the expression for current is:

i(q) = A*exp {- (q - a) /t} + (E/Z)*sin (p - b)*exp {- (q - p) /t} .

The voltage across the inductor is obtained to be

vL(q ) = vs(q) - R*i(q) , for a < q < p and

vL(q ) = - R*i(q) , for p < q < (2p + a) .

vs(q) = E*sin (q).

It is preferable to normalize vs with respect to E and the current with respect to E/R and then the only value that is required to be known for solving for the current is t. The applet shown below simulates this circuit. You have to key-in the ratio t in the text-field to the left of the button and the firing angle in degrees in the text-field to the right of the button and then click on the button next to it. Do not key-in a NaN.

click here to open the applet

 
TO THE TOP