Page 31 – Controlled Rectifiers (GATE Practice)
Subject: Power Electronics
Topic: Single Phase Fully Controlled Rectifier
Level: GATE / PSU
🔹 Important Formula
For Single Phase Fully Controlled Bridge (R Load):
Vavg = (2Vm / π) cos α
🔹 Concept Question
Q1. If firing angle α increases, what happens to output voltage?
As α increases → cos α decreases → Output voltage decreases.
🔹 Numerical Problem 1
Given:
Input: 230V rms
α = 60°
Find: Average output voltage.
Vm = √2 × 230 = 325 V
Vavg = (2 × 325 / Ï€) cos 60°
= (650 / 3.14) × 0.5
= 207 × 0.5
= 103.5 V
🔹 Numerical Problem 2 – Inverter Mode
If α > 90° → cos α negative → Vavg negative → Inverter operation.
Condition: α > 90°
🔹 GATE Trick Points
- Maximum output at α = 0°
- Zero output at α = 90°
- Negative output when α > 90°
- Ripple frequency = 2f
Quick Revision
Vavg = (2Vm/π) cos α
Vm = √2 Vrms
Practice Daily – Shaktimatha Learning
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