Why the transformer will burn if DC supply is given?

Gajendra Singh

• Oct 30th, 2017

If we apply DC at input end then there will be no emf induced in the primary winding, As e=N*d(flux)/dt. Also leakage reactance (X1)and magnetizing reactance (Xm) will also be zero, coz (X=2πf) and f...

saif

• Oct 2nd, 2017

The induced emf in transformer is change of flux linking with number of turns.... if we apply dc to the transformer there is no flux changes in transformer..... emf not induced...mainly winding will be burn

Answer Question  Select Best Answer

Read Best Answer

Editorial / Best Answer

KaranSorout  

 Profile Answers by KaranSorout Questions by KaranSorout

• Member Since Jul-2006 | Jul 13th, 2006

---

The power ratio between Star to Delta is 1:3

Explanation:

 

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

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

Now assume any type of load; for simplicity I?m assuming it a only resistive load.

And let it be ?R? per phase.

 

For Delta connected load:

 

Calculation for per phase power; P_D= I²R

 

Where I ? load current (per phase)

And,

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

So,

            P_d = (?3V_s/R )²R = 3V_s²/R  watts per phase.

For 3 phases:

            P_3D = 3P_d = 3*3V_s²/R = 9V_s²/R watts.

 

Now for Star connected load:

 

P_S = I²R = (V_s/R)²R = V_s²/R watts

For 3 phases: P_3S = 3P_S = 3 V_s²/R watts

 

Conclusion:

P_3S / P_{3D  =}  3V_s²/R / 9V_s²/R = 1/3

It may be better concluded by drowing figures. If any variations, can connect to me through karan.sorout@gmail.com  

RUP KAMAL KUTUM

• Feb 3rd, 2018

Well first you assumed voltage per phase as Vs and Line voltage as sqrt(3) x Vs: Which is for star connection. Then, you assumed the same thing for Delta Connection(where line and phase voltages are t...

Anbumozhi R

• Dec 3rd, 2017

Power is Same. Whether it is star to Delta conversion or Delta to star conversion. Power is 1:1

Improve Answer