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Lesson 11 'විදුලි යන්ත්‍ར හා බල පද්ධති' (Electrical Machines & Power Systems) හි ප්‍රධාන මාතෘකා:

• ⚡ DC Motors — Series, Shunt, Compound; speed control methods
• 🔄 AC Induction Motor — Squirrel cage, Wound rotor; slip formula
• 🔁 Synchronous Motor — principle, construction, applications
• 🔌 AC & DC Generators — EMF equation, output characteristics
• 🔃 Three-Phase Transformer — Star/Delta (Y/Δ) connections
• ▶️ Motor Starting — DOL, Star-Delta, Auto-transformer, Soft starter
• 📊 Power Factor Correction — capacitor banks
• 🏭 Power Generation (Thermal/Hydro/Solar) & Grid Transmission
• 🛡️ Switchgear & Protection — MCBs, Contactors, Relays

DC Motor — DC supply, easily controllable speed:

• Series — high starting torque, variable speed (traction, cranes)
• Shunt — constant speed (lathes, fans, pumps)
• Compound — combined characteristics

AC Induction Motor — AC supply, simple & robust:

• Squirrel cage — low maintenance (pumps, fans, compressors)
• Slip ring — adjustable starting torque (heavy loads)

Slip (s) = (Ns − N) / Ns  |  Ns = 120f/P

AL Tech Hub (altechhub.lk) හි Lesson 11 Downloads කොටසෙන් නොමිලේ ලබාගත හැකිය:

• 📄 Full Notes PDF — 7.8 MB, 104 pages
• 📄 DC & AC Motors Guide — 3.2 MB, 32 pages
• 📄 Generator & Alternator Notes — 2.6 MB, 26 pages
• 📄 Motor Starting Methods — 2.0 MB, 20 pages
• 📄 Power Systems & Grid — 2.4 MB, 24 pages
• 📄 Formula Sheet — 0.7 MB, 4 pages
• 📊 Slide Deck (PPTX) — 10.5 MB, 66 slides
• 📝 Practice Q&A (DOCX), Past Papers, 🗜️ Complete Bundle (ZIP 38 MB)

DOL (Direct On-Line) — Full voltage direct:

• Starting current = 6–8× rated; Simple, low cost
• Small motors (< 5 kW)

Star-Delta (Y-Δ) Starter:

• Starting: Star → Running: Delta
• Starting current & torque = 1/3 × DOL; Medium motors (5–30 kW)

Auto-transformer Starter:

• Reduced voltage via transformer tap — better torque than Star-Delta
• Large motors (> 30 kW)