# Difference between single phase and three phase system?

Discussion in 'Electrical | Electronics | Communications' started by Chaitali Sumita, Aug 15, 2009.

### Chaitali SumitaCertified CEan

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hiii.....
i m a 3rd year student of Electrical and Electronics Engg.......
what is phase ???what is the difference between single phase and three phase system???

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Ha ha . I used to ask this question in Interviews to newbie electrical engineers. 9/10 would have no clue.

### skipperCertified CEan

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Phase is generally the difference between two waves - of any kind. In electrical systems the phase is (of) AC; this is generated in three distinct phases all 120[sup]o[/sup] apart.

In any street there are houses at different AC phases (all dwellings are connected to one of three single phases). Electric motors can use all three (star or triangular windings) so they're more efficient.

ps. another word for "phase difference" is gauge. Gauge theories (like QFT) use different phases than AC - like the Coulomb gauge; quantum gauges are fundamental, like the charge of the electron.
So now maybe, you know...? (Don't take my word for it, though)

### AMITBOSECertified CEan

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Three phases means:r,y,b.
Each seperated by n angle of 120

yes The 3 phases are RYB which are seperated by an angle 120 which was generated because of conductors.Generally 3 phase systems are used at high loads and voltages.

### sarasCertified CEan

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Well in case of single phase system,the main aim is to distribute the power like transformer.Here voltage vary simultaneously and current in the conductor reach it's peak value(different voltage,different current) simultaneously.

And in case of 3 phase system,at the given voltage,the current in the conductors(3 or more conductor) reach their peak value(max value) sequentially at given clock pulse(means different cycle).

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any electrical quantity can be represented on complex plane where the two axis are real and imaginary. Now any quantity say Current is represented by a moving vector on this plane. fine? Now the angle of this current with real axis is time varying. If the other current I2 has the angle other than the I1 angle than they are called with phase difference. The angle of the current with real axis is called phase. In case of three phase, we have three current(or voltages) having mutual phase difference of 120 degree. Have u followed???;-)

### ramkumar.jCertified CEan

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hi Chaitali Sumita
phase means the differnce between the waves, through which the current flows. 1 phase consists of 3 wires , 1 phase 1 neutral and 1 stay wire. 3 phase consists of 5 wires , 3 phases(R, Y, B), 1 neutral and 1 stay wire. In most of the transformers 3 phases are mostly used except the road side transformers because the voltage of 3 phase is 440v. In domestic appliances 1 phase is used because the voltage required is 230v.

### vibhor_oneCertified CEan

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Can anybody explain me why single phase connetion at 230 volts and the equivalent three phase connection at 440 volts whereas multiple of 230 volts by three time makes it 690 volts???

### jigchinCertified CEan

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See,basically phase means number of conductors used for generation of emf......Therefore,single phase means single conductor is used for generation of emf & three phase means three conductors are used i.e R,Y,B for generation of emf.
i am dam sure about my phase concept

### Chaitali SumitaCertified CEan

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thank you...it really helped me(about phase)....but little bit ellaboration is expected.....so can you please ellaborate it liitle more????

proud to be an CEAN

### RajendramaliCertified CEan

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You are measuring it by taking reference or neutral point & it can be only one reference.
When you are measuring voltage 440 volts , it's between two phases & single phase with respect to neutral or earth will give you 230V. OK !!!

### sunil maliwalCertified CEan

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single phase is only one phase and netural and three phase there are three phase R,Y,B.and it is separated by an angle 120degree.

### sunil maliwalCertified CEan

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In wiring which system is most used?

### manoj_2allCertified CEan

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1. Single phase voltage is compare then three phase voltage is very low for ex- 1 phase 240v < 3 phase 440v.

2. Three phase can make rotating magnatic field but single phase can not make rotating magnatic field.

3. In three phase is phase sequence but single phase is not phase sequence.

### shabsCertified CEan

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give me the theory of load test on three phase transformers and the theory of measurement of three phase power using two wattmeter method

### AlienatorApprentice

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also.....i dont get why the phase difference in 3 phase should always be 120 degrees....what happens if they vary??and what happens if all the three are in same phase(i mean RYB)

### steelomaticCertified CEan

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Generators are circle, 360 degree i.e 3 phases each 120 degree and they vary from load side. and they cannot be in same phase practically. but theoretical just sum them up if so.

### AlienatorApprentice

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Electrical & Electronics
[HR][/HR]can any one tell me how the phase difference in 3 phase system is maintained exactly at 120 degrees? what happens if it changes?also what happens if RYB are in phase?