Question

If the load reactance is now changed to a very large series inductance, calculate the

firing angle required to achieve a DC output load current of 20A.

with rload =10ohm and 1.76ohm reactance connected to it

Question 2 (20 Marks): A 3-phase SCR bridge feeds a load comprising a 10Ω resistor and 1.7662 reactance connected in series, from a 3-phase 415V, 50Hz AC supply. a) For a firing angle of a (i.e. diode operation), calculate the average DC output (6 marks) voltage, and the maximum and minimum instantaneous DC output voltages. ciavg)560.25V oCan. b) Using appropriate approximations, identify the firing angle α at which the load current will just become discontinuous. (4 marks) Page 4

Answer 1

CPscuit Diaqram- т. 尺 Loa 3phase SCR blidge ectifier average outut Volt*gev 3Vmu cos where →千1Ying angle VmL_→ m#ximum Line volta qes y,sx.is 586. B, valts. 9n the above 9uestion as he load reactan^ is will beuome Constant ' « avvrage Vo ltaqe ocroas indui to^ is Zeo ed to very large Value s。Haa load cum n t ven as I.- toA So auenge output voltage Us: x102 200 volts

doo= "3 x 5-8681 3.14 Cos 3673 so the fining angle Teguired to auhieve output Crment