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What is the power ratio between power in star and delta circuit?

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Question ajoutée par muhammad arif , Assistant Engineer , Phoenix armour
Date de publication: 2013/11/24
muhammad arif
par muhammad arif , Assistant Engineer , Phoenix armour

As we know the main function of transformer is to transfer power from one ckt to another ..so ratio will same on both side of transformer..it only change the ratio of voltage and current .

Mahmoud Mohammed
par Mahmoud Mohammed , Technical Manager , Optimum Engineering and Trading Company

The power ratio between Star to Delta is1:3

hassan qutb
par hassan qutb , Facility&Engineering Manager PMP. , مقاولات خاصه

The inpot power = The output power + the power losses

Maher Alasli
par Maher Alasli , service engineer , UNITED WEAVERS

 the power ratio in the circuit if the  Star 1 the  delta will be3 and the calculation answer above by another college and for me i remamber only1/3

Nabil Akram PMP
par Nabil Akram PMP , Project Manager , Mohammad Al-Ojaimi Contracting Est.

Power ratio is1,

As for star:

Pt=P1+P2+P3                         (P1 for phase1 ,P2 for phase2 and P3 for Phase3)

P=P1=P2=P3=Vph*Iph*cos theta

Pt=3*P

As in star connection Vline=(3)^1/2*Vph

so

Pt=3*(Vline/(3)^1/2)*Iph*cos theta

Pt-star=(3)^1/2*Vline*ILine*cos theta   as ILine=Iph

 

Similarly for delta connection

Pt=P1+P2+P3                         (P1 for phase1 ,P2 for phase2 and P3 for Phase3)

P=P1=P2=P3=Vph*Iph*cos theta

Pt=3*P

As in delta connection ILine=(3)^1/2*Iph

Pt=3*Vline*(Iph/(3)^1/2)*cos theta             as Vline=Vph

Pt-delta=(3)^1/2*Vline*ILine*cos theta   as Vline=Vph

 

As

Pt-star =Pt-delta

so

Pt-star/Pt-delta=Pt-delta/Pt-star=1

 

Leonardo Banzali
par Leonardo Banzali , Electrical Maintenance-trainer , Sadara Chemical Company

The power ratio is1:3 when referring this to a wye-delta motor starting.

Waqar Ahmed
par Waqar Ahmed , Instrument Technician , ADNOC Gas Processing

normally it is1:3 ratio

abanob Emil
par abanob Emil , مهندس تخطيط , كولاس ريل

The power ratio between Star to Delta is1:3

Explanation:

 

Lets suppose Vs be the supply voltage per phase.

So the line voltage of the supply will be Ö3Vs.

Now assume any type of load; for simplicity Im assuming 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 à load current (per phase)

And,

I = Ö3Vs/R       {as line voltage of the supply is directly applied to the phase of the delta load}

So,

            Pd = (Ö3Vs/R )2R =3Vs2/R  watts per phase.

For3 phases:

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

 

Now for Star connected load:

 

PS = I2R = (Vs/R)2R = Vs2/R watts

For3 phases: P3S =3PS =3 Vs2/R watts

 

Conclusion:

P3S / P3D  =  3Vs2/R /9Vs2/R =1/3

Asif Iqbal
par Asif Iqbal , Asistant Manager , M/s Jindal Steel & Power Ltd

power is always constant in Xmer

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