In the given diode rectifier circuit, The diodes D1, D2 & D3 are connected to phases R,Y and B respectively as shown. The phase sequence is R-Y-B. The diode D1 would conduct from

Concept: Given circuit is a three-phase half wave rectifier circuit. In this circuit any diode will conduct when voltage across them will be maximum and remaining will be off.

Let diode D₁ belongs to R-phase, D₂ belongs to Y phase and D₃ belongs to B-phase. 

Hence, diode D₁ will conduct when voltage in R-phase is maximum.

Let us see the waveform of three phase voltages.

V_RN = V_m sin wt

VYN = Vm sin (wt - 120°)

VBN = Vm sin (wt + 120°)

It is clearly visible from the waveform that R-phase voltage is maximum from 30° to 150° 

∴ Diode D₁ would conduct from 30 to 150 degrees.

Therefore, correct option is (3).