The designed capacity of the transformer was 1600 watt. The utility company is in shortage of such wattage, so they used two 800 watt transformers in parrallel. The utility company uses only one circuit breaker after the parallel connection. The custmer says it is not correct there should be two separate breakers for each transformer. Which connection is accseptable.

VEERENDRAKUMAR.CH

 Profile Answers by VEERENDRAKUMAR.CH Questions by VEERENDRAKUMAR.CH

• Jan 28th, 2011

when one CB used:if fault occurs on any one transformer that fault will effect the another transformer so two CB must be needed 

appersundaram

 Profile Answers by appersundaram Questions by appersundaram

• Mar 27th, 2010

We can use two circuit breakers in parallel, but we should connect the mastertrip relay contact of either breaker should be wired to trip the other breaker as well.

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KaranSorout  

 Profile Answers by KaranSorout Questions by KaranSorout

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

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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

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