Question

A 3-ϕ, 6 pulse diode bridge rectifier is supplied by (100π)/√6 V(rms/phase), 50 Hz. Find the average output voltage.
1. 300 V
2. 900 V
3. 100 V
4. 500 V

Answer 1

Correct Answer - Option 1 : 300 V

Concept:

The output voltage of a three-phase 6 pulse bridge rectifier is given by,

\({V_0} = \frac{{3{V_{ml}}}}{\pi } = \frac{{3\sqrt 3 {V_{mp}}}}{\pi }\)

Where V_ml is the maximum line voltage

V_mp maximum phase voltage

Calculation:

Given that, rms supply phase voltage (V_rms) = (100π)/√6 V

Maximum phase voltage (V_ph) = 100π/√3 V

Average output voltage \( = \frac{{3\sqrt 3 \times \frac{{100\pi }}{{\sqrt 3 }}}}{\pi } = 300\;V\)

Important Points:

	Single-phase full-bridge rectifier	Three-phase full bridge rectifier
Average output voltage	\({V_0} = \frac{{2{V_m}}}{\pi }\)	\({V_0} = \frac{{3{V_{mL}}}}{\pi }\)
Average output current	\({I_0} = \frac{{{V_0}}}{R}\)	\({I_0} = \frac{{{V_0}}}{R}\)
Average diode current	\({I_{DA}} = \frac{{{I_0}}}{2}\)	\({I_{DA}} = \frac{{{I_0}}}{3}\)
RMS diode current	\({I_{DR}} = \frac{{{I_0}}}{{\sqrt 2 }}\)	\({I_{DR}} = \frac{{{I_0}}}{{\sqrt 3 }}\)
Average source current	\({I_{SA}} = 0\)	\({I_{SA}} = 0\)
RMS source current	\({I_{SR}} = {I_0}\)	\({I_S} = {I_0}\sqrt {\frac{2}{3}} \)