A single-phase full converter is connected to 230 V, 50 Hz. The load is R = 10 Ω with a very large inductance. For α = 30°, verify.1.Average output voltage is approximately 179.3 V.2.The RMS value of the input current is 17.93 A.3.The fundamental power factor is 0.866.Which of the statements are correct?

Correct Answer: C - 1, 2 and 3

Quick Concept Explanation

Firing angle controls average DC voltage; the AC-side current is non-sinusoidal and its fundamental is displaced approximately by α. Vdc=(2√2×230/π)cos30°≈179.3 V. With R=10 Ω and highly inductive continuous current, Id≈17.93 A. Key relation: 1φ: Vdc=(2Vm/π)cosα≈0.9Vrms cosα; 3φ: Vdc≈1.35V_LL cosα.

Exam focus: Large load inductance → nearly constant DC current. Common trap: Distinguish displacement factor cosα from total power factor including distortion.

Statement-wise Verification

• Statement 1 - Correct.
  Average output voltage is approximately 179.3 V.
  Vdc=(2√2×230/π)cos30°≈179.3 V.
• Statement 2 - Correct.
  The RMS value of the input current is 17.93 A.
  With R=10 Ω and highly inductive continuous current, Id≈17.93 A.
• Statement 3 - Correct.
  The fundamental power factor is 0.866.
  The fundamental displacement factor is cos30°≈0.866.

Core Concept

A fully controlled bridge feeding a highly inductive load operates with nearly continuous DC current. Firing angle controls average DC voltage; the AC-side current is non-sinusoidal and its fundamental is displaced approximately by α. In three-phase bridges each thyristor conducts for 120 electrical degrees under continuous current.

Formula / Key Relationship

1φ: Vdc=(2Vm/π)cosα≈0.9Vrms cosα; 3φ: Vdc≈1.35V_LL cosα.

Step-by-Step Check

Vdc=(2√2×230/π)cos30°≈179.3 V. With R=10 Ω and highly inductive continuous current, Id≈17.93 A. The fundamental displacement factor is cos30°≈0.866.

Why the Other Options Are Wrong

Option A is incorrect because it omits correct statement(s) 3. Option B is incorrect because it omits correct statement(s) 1. Option D is incorrect because it omits correct statement(s) 2.

Exam Shortcut / Approach

Large load inductance → nearly constant DC current.

Common Mistake

Distinguish displacement factor cosα from total power factor including distortion.

Quick Revision

Average Output and Input Current is linked with Single-Phase Full Converter, Controlled Rectifiers and Power Electronics. Large load inductance → nearly constant DC current.