Answer Posted / baswaraj

The power ratio between Star to Delta is 1:3

Here is the Explanation:

Let?s suppose Vs be the supply voltage per phase.

So the line voltage of the supply will be ?3Vs.

Now assume any type of load; for simplicity assume it a
only resistive load.

And let it be ?R? per phase.



For Delta connected load:



Calculation for per phase power; PD= I2R



Where I ? load current (per phase)

And,

I = ?3Vs/R {as line voltage of the supply is directly
applied to the phase of the delta load}

So,

Pd = (?3Vs/R )2R = 3Vs2/R watts per phase.

For 3 phases:

P3D = 3Pd = 3*3Vs2/R = 9Vs2/R watts.



Now for Star connected load:



PS = I2R = (Vs/R)2R = Vs2/R watts

For 3 phases: P3S = 3PS = 3 Vs2/R watts



Conclusion:

P3S / P3D = 3Vs2/R / 9Vs2/R = 1/.

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