Generation of three-phase voltages
Let three coils are placed in a uniform magnetic field. These coils arc placed 1200 apart as shown in the figure. If these coils are rotated at the same speed in the magnetic field, three voltages will be induced in the coils. These voltages will be 1200 apart in phase from each other e.g.
The order in which the voltages will reach the peak or maximum value is known as phase-sequence For the given voltage we say that phase order or phase sequence is 1 -2- 3.
If the direction of rotation of coils is reversed then the phase sequence will also change and would become 1 -3- 2 This sequence means 3 is 1200 behind 1 and 2 is 1200 behind 3. There are two general connections in three phase systems.
1) Star or Y connection and
2) Delta or mesh or connection.
If the three coils arc placed such that they have one common terminal (known as neutral), then it is a star. or Y connection as shown in fig.
It is known as 3 phase, 4 wire star connected system. If three coils are placed such that they forms a close circuit, then it is known as delta or mesh connection. It is always a 3-phase, 3 wire system.
A.C. CIRCUITS TOPIC
- Introduction Of AC Circuits In Electrical Engineering
- How emf is induced in single phase system ? single phase generation .
- Explain what is ac quantity : and Advantages of AC over DC in circuits
- What is waveform, amplitude, cycle, time-period, phase & phase difference
- Define RMS & average value as applied to A.C. voltage & current
- What is form factor? crest factor? peak factor? & power factor? in ac circuits
- what is phasor diagram, phasor algebra, leading & lagging ac quantities
- Phasor representation of alternating quantities – resistive, inductive, capacitive
- What is R-L-C series connection for A.C. circuit ? Explanation
- What is series combination of R-L circuit ? Explanation
- Define what is active power, reactive power, apparent power & power factor
- Explain what is series combination of R-C circuit in electrical engineering
- What is simple parallel AC circuits ? Explanation -electrical engineering
- Resonance as applicable to simple RLC series circuit? effect on circuit performance
- Explain three phase generation of voltage ? electrical engineering
- Explain in detail about what is star and delta three phase system ?
- Relation between phase voltage & line voltage in case of balanced star connected load
- relationship between line current & phase current for delta connected 3 load
- Relation between power consumed in a balanced star & delta connection