star delta connection used in reduce the starting current
at 3 times . how its reduce the current please explian .

Answer Posted / kumar

all of us know in star Vl=1.732Vp & Il=Ip, at start as current is limited to phase current, thats why motor dosent draw more current.and for delta it is normal cond. i.e.415v. get applied across each wdg. insted of 250(as in star) & line current is limited to 1.732 times phase current. Motor remains in str for 4-5 Sec only.Also power consumption in both cases remain same(can be proved).
But it is also possible that motor can draw more current in star position due application of reduced voltage,also the change in such vtg. will affect torque.
If possible try to find out derrivation for vtg. & current in star & delta connected resistance.

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