Answer / guguloth shobhan

every signal has hormonics that are 1st,2nd,3rd,4th,5th..so on.even hormonics will be zero for sinusoidal signal becoz of it is odd function.So reamining are 1st,3rd,5th,7th,.....but higher order are not much effected that are 7th,9th...so on. SO remaining are 1st,3rd,5th.
5th order hormonic wiil be zero due to symmetrical(120 displacement).now have to eliminate 3rd hormonic ,it will be eliminate by using 3phase supply.1st hormonics is fundamental hormonic that is desirable one.
for above reason , we are using 3 phase supply.

Answer / mahesh

it needs many slip rings, converters,cross arm long increased,cost incrsd,,,,,etc

Answer / sanjayjssate

The power generates due to change of flux passing through armature, in 3 phase system the displaced flux at equal angle gives max output without hindering other flux path. That is why 3 phase generation is in practice. It is also very economical.

Answer / sandy

electrical degree is considered for generate the electrical phase there are 360 electrical, so we can generate only 3 phase 120 degree electrical per phase.
 

Answer / rakesh

We need min 3 ac phases to produce an alternately rotating , self-starting, magnetic field which is basic need to produce EMF and hence generation of power. And for 360 total electrical degree ,there we have 3 , 120 apart degree electrical phase. so no 2 phase production popular, now same may be achived by 4phase 5 phase system , but it needs as many slip rings,coil's, insulation to produce as well as converters,cross arm long increased to convert and transmit

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