Test: Phase Controlled Rectifiers - 1 - Electrical Engineering (EE) MCQ

As the supply voltage is 400 sin 314t
V_m = 400 V,
Peak invesre voltage (PIV)

RMS value of current = 20 A 
Average value of current,

Input power factor = 

For α = 90^o
Input power factor = 
= 0.6363 lag

The average output voltage of a semiconverter 
Maximum output voltage = 

1 + cos α = 0.5
α = 120^o
Average load current, 

Average output voltage 


L_S = 17.11 mH
Average load current 

µ = 6.627^o

The average output voltage for a single-phase full converter is

Maximum voltage across SCR in single-phase mid-point converter is 2V_m. Therefore, this converter can be design for a maximum voltage of

∴ Maximum average power that the mid-point converter can handle is

Circulating current gives rise to more losses in the converters, hence the efficiency and power factor are low. Thus, statement-1 is false.
In a non-circulating current type dual converter, the normal delay period of 10 to 20 ms is required while no delay period is required in circulating current type dual converter. Therefore, circulating current type dual converter is faster than non-circulating type dual converter. Thus, statement-2 is true.
As the dual converter with circulating current has to handle load current as well as circulating currents, therefore the thyristors are rated for higher currents. Hence statement-3 is false.

In case “four quadrant operation" is required without any mechanical changeover switch, two full converters can be connected back to back to the load circuit. Such an arrangement using two converters in antiparailel and connected to the same dc load is called a “dual converter."