Chapter 5 lecture
- 1. CHAPTER 5 : THREE PHASE SYSTEM Objectives: Know basic principles of 3Φ system List advantages and application of 3Φ system compared to 1Φ system Know 3Φ e.m.f generation Identify star & delta connection Determine VPH, IPH, VL,IL & power in 3Φ system
- 2. INTRODUCTION • 3Φ system is a combination of three 1Φ system • In 3Φ system balanced system, power comes from 3Φ AC generator • 3Φ generators have 3 coils fixed at 120° to each other rotating in magnetic field. • 3Φ system are use for transmission and distribution of electricity and also in industry
- 3. ADVANTAGES OF 3Φ SYSTEM vs 1Φ SYSTEM • Weight less than 1Φ circuit of same power rating • Have wide range of voltages • Smaller in size &higher power factor thus more efficient • Steady torque output and ability to self start • Inherent benefits for high power transmission • Produce constant amount of power in the load
- 4. GENERATION OF 3Φ SUPPLY There are two ways to generate 3Φ supply. Moving magnetic field while coil is permanent. Moving coil while magnetic field is permanent.
- 5. GENERATION OF 3Φ SUPPLY Generation for R phase (same as single phase generation)
- 6. GENERATION OF 3Φ SUPPLY Generation for Y phase (coil rotate 120° so that it will equal with R phase, thus Y lags R by 120°)
- 7. GENERATION OF 3Φ SUPPLY Generation for B phase (coil rotate 240° so that it will equal with R phase, thus B lags R by 240°)
- 8. GENERATION OF 3Φ SUPPLY Phasor diagram for 3 phase system
- 9. CONNECTION IN 3Φ system Physically 3Φ system consist of three different coils. Each phase coils have 2 terminal and required 2 conductor as connection So 6 conductors will be used as in 3Φ connection This kind of connection is difficult and will cost more. To overcome this problem, 3Φ supply usually connected in DELTA or STAR connection
- 10. CONNECTION IN 3Φ system a) STAR/ WYE Connection Physical connection Conventional representation diagram
- 11. CONNECTION IN 3Φ system b) DELTA Connection Conventional representation Physical connection diagram
- 12. REVIEW • Two ways to generate AC rotating coil, permanent magnet field or vice versa. • Each voltage separed by 120° • IN equal to zero when load is balanced.
- 13. CALCULATION STAR CONNECTION DELTA CONNECTION Relationship between VL and Vph Relationship between IL and Iph
- 14. FORMULA USE IN THREE PHASE CALCULATION
- 15. EXERCISE