CrazyEngineers Archive
Old, but evergreen and popular discussions on CrazyEngineers, presented to you in read-only mode.
@Chaitali Sumita • 15 Aug, 2009
hiii.....
i m a 3rd year student of Electrical and Electronics Engg.......
i was curious about
what is phase ???what is the difference between single phase and three phase system???😁
@Aashish Joshi • 15 Aug, 2009 Re: "phasal" question

i think these two articles should answer your query..

1. Three-phase - Wikipedia, the free encyclopedia
2. Three-phase electric power - Wikipedia, the free encyclopedia
@Kaustubh Katdare • 15 Aug, 2009 Ha ha 😀. I used to ask this question in Interviews to newbie electrical engineers. 9/10 would have no clue.

Anyone wishes to answer this in your own words?
@skipper • 16 Aug, 2009 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)
@AMITBOSE • 02 Sep, 2009 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.
@saras • 23 Dec, 2009 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).
@chirag_kotadia • 28 Dec, 2009 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.j • 12 Jan, 2010 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_one • 13 Jan, 2010 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???
@jigchin • 30 Jan, 2010
Chaitali Sumita
hiii.....
i m a 3rd year student of Electrical and Electronics Engg.......
i was curious about
what is phase ???what is the difference between single phase and three phase system???😁
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 Sumita • 26 Feb, 2010
jigchin
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.
thank you...it really helped me(about phase)....but little bit ellaboration is expected.....so can you please ellaborate it liitle more????😒

waiting eagerly for your reply.....


proud to be an CEAN
@Rajendramali • 02 Mar, 2010
vibhor_one
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???
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 maliwal • 02 Mar, 2010
Chaitali Sumita
hiii.....
i m a 3rd year student of Electrical and Electronics Engg.......
i was curious about
what is phase ???what is the difference between single phase and three phase system???😁
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 maliwal • 02 Mar, 2010 In wiring which system is most used?
@manoj_2all • 30 Mar, 2010 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.
@shabs • 14 Aug, 2011 give me the theory of load test on three phase transformers and the theory of measurement of three phase power using two wattmeter method
@Alienator • 14 Aug, 2011 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)
@steelomatic • 14 Aug, 2011
Alienator
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)
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.
@Alienator • 17 Aug, 2011 [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?
@Ankita Katdare • 27 Mar, 2014 There are 360 degrees in a full cycle so 120 is one-third so each of the three phases is equally spaced delivering power evenly to the load.

@lal Could you please answer this?
@lal • 27 Mar, 2014 To have a three phase output, the R, Y and B windings should be electrically seperated at 120 degrees in an alternator. Electrical degrees need not be the same as mechanical degrees. It depends on the number of poles. If only one pair of poles is used, electrical and mechanical degrees will be the same. That is, to have a three phase output, simply wind the armature (stator) in a way that the coils are mechanically 120 degrees apart around the circumference.

Now, why isn't electrical and mechanical degrees the same? The field (rotor) of an alternator can have many number of poles. And the poles will be arranged alternately as north and south on the rotor. But then, one complete cycle of emf will be induced in a coil when a pair of poles passes over it. That means, in the case of a four pole alternator, the rotor has to rotate only 180 degrees to generate one complete cycle of emf where as it was 360 for two poles.

If the phase differences are not maintained at 120 degrees, it simply isn't a three phase sytem. It can't be balanced without equal phase differences. Even the voltage across the phases will differ. That would then simply be three phase at random phase differences, but not a three phase system.

If R, Y and B are in phase, those are three single phase supplies named R,Y and B without any phase difference, but not a three phase AC supply system. Could be three parallel branches of a single phase AC system which are named R, Y and B just for the sake of it 😁
@Ankita Katdare • 21 Dec, 2015 An informative video I came across -
A simple explanation to three phase power.
@silver123 • 23 Dec, 2015 Single phase power is used in most homes. Able to supply ample power for most smaller customers, including homes and small, non-industrial businesses. Adequate for running motors up to about 5 horsepower; a single-phase motor draws significantly more current than the equivalent 3-phase motor, making 3-phase power a more efficient choice for industrial applications.
Three phase power is used common in large businesses, as well as industry and manufacturing. Increasingly popular in power-hungry, high-density data centers. Expensive to convert from an existing single-phase installation, but 3-phase allows for smaller, less expensive wiring and lower voltages, making it safer and less expensive to run. Highly efficient for equipment designed to run on 3-phase.
@silver123 • 23 Dec, 2015 Single phase power is used in most homes. Able to supply ample power for most smaller customers, including homes and small, non-industrial businesses. Adequate for running motors up to about 5 horsepower; a single-phase motor draws significantly more current than the equivalent 3-phase motor, making 3-phase power a more efficient choice for industrial applications.
Three phase power is used common in large businesses, as well as industry and manufacturing. Increasingly popular in power-hungry, high-density data centers. Expensive to convert from an existing single-phase installation, but 3-phase allows for smaller, less expensive wiring and lower voltages, making it safer and less expensive to run. Highly efficient for equipment designed to run on 3-phase.
@silver123 • 23 Dec, 2015 Single phase power is used in most homes. Able to supply ample power for most smaller customers, including homes and small, non-industrial businesses. Adequate for running motors up to about 5 horsepower; a single-phase motor draws significantly more current than the equivalent 3-phase motor, making 3-phase power a more efficient choice for industrial applications.

Three phase power is used common in large businesses, as well as industry and manufacturing. Increasingly popular in power-hungry, high-density data centers. Expensive to convert from an existing single-phase installation, but 3-phase allows for smaller, less expensive wiring and lower voltages, making it safer and less expensive to run. Highly efficient for equipment designed to run on 3-phase.
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