Page 36 – 12-Pulse Converter (HVDC Application)
Subject: Power Electronics
Topic: 12-Pulse Rectifier
Level: GATE / PSU Advanced
🔹 Why 12-Pulse Converter?
- Reduces harmonics significantly
- Used in HVDC transmission
- Improves power factor
- Lower ripple in output voltage
🔹 Construction
Two 6-pulse converters connected in series or parallel with phase shift of 30° using transformer.
- One converter fed from star-star transformer
- Other from star-delta transformer
- Total SCRs used = 12
🔹 Average Output Voltage
Vavg = (3√2 VLL / Ï€) cos α
(Same as 6-pulse but ripple reduces)🔹 Ripple Frequency
Ripple frequency = 12f
For 50 Hz supply → 600 Hz ripple🔹 Harmonics Reduction
5th and 7th harmonics significantly reduced. Lower Total Harmonic Distortion (THD).
🔹 GATE Important Points
- Phase shift = 30°
- Used in high power applications
- Less filtering required
- Higher cost than 6-pulse
Quick Revision
12-Pulse → Two 6-Pulse Converters
Ripple frequency = 12f
Used in HVDC
Advanced Converter Series – Shaktimatha Learning
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