POWER ELECTRONICS – PAGE 11
Full Wave Controlled Rectifier (Single Phase)
1️⃣ Introduction
A Full Wave Controlled Rectifier uses two SCRs (midpoint type) or four SCRs (bridge type) to control both half cycles of the AC input.
It provides better output and higher average voltage than half-wave rectifier.
2️⃣ Working Principle (Midpoint Type)
🔵 Positive Half Cycle
- SCR1 is forward biased
- Triggered at firing angle α
- Conduction from α to π
🟠Negative Half Cycle
- SCR2 becomes forward biased
- Triggered at π + α
- Conduction from π + α to 2π
3️⃣ Average Output Voltage (R Load)
Vavg = (Vm / π) (1 + cos α)
Compare with Half Wave:
Half Wave → Vm / 2Ï€ (1 + cos α) Full Wave → Vm / Ï€ (1 + cos α)
👉 Full wave gives double output
4️⃣ Special Cases
- α = 0° → Maximum output (2Vm / Ï€)
- α = 90° → Reduced output
- α = 180° → Zero output
5️⃣ Advantages Over Half Wave
- Higher average output voltage
- Lower ripple
- Better transformer utilization
- Improved efficiency
6️⃣ GATE / PSU Focus
- Difference between half & full wave
- Waveform identification
- Average voltage formula
- Bridge vs midpoint comparison
Important: For full controlled bridge rectifier, formula becomes Vavg = (2Vm / π) cos α
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