Answer Posted / engr. ziaul ashraf shafi

Answer #5 is fine.. but i want to add something more..
normally this test is made in star side of the transformer.
the result should be varified like following:
1) if 2u-2n is fed by 230 volt.
- the nearest phase (2v-2n) will experience the 85% to 90%
of fed voltage at 2u-2n. (i mean 2v-2n = 195.5 to 207
volt). And the distant phase (2w-2n) will experience the
10% to 15% of fed voltage at 2u-2n. (i mean 2w-2n = 23 to
34.5 volt).
2) if 2v-2n is fed by 230 volt.
- then the fed pahase is middle phase, and both other phase
are magnetically in equal distance.. so the measured
voltages in 2u-2n or 2w-2n = 50 % (or 40 to 60 % is also
accaptable). so the 2u-2n or 2w-2n = 92v to 138v is
accaptable.
3) if 2w-2n is fed by 230 volt.
- the nearest phase (2v-2n) will experience the 85% to 90%
of fed voltage at 2w-2n. (i mean 2v-2n = 195.5 to 207
volt). And the distant phase (2u-2n) will experience the
10% to 15% of fed voltage at 2u-2n. (i mean 2w-2n = 23 to
34.5 volt).

*If the results are found beyond these above mentioned
limits then other tests (like open ckt test with rated
voltage) should be performed to be sure about core and
winding.
*You can measure and note down the current of each injected
phase. it will give u a signaficant idea about winding. if
the winding has an inter-tern short then the faulty phase
will draw comapretively large magnetizing current like 3A
or 5A, wheather other phases will draw 60mA to 100mA.
*Remember, the magnetic reluctance path of a core is not
lenier, so the result veries itself. But big differences
are remarkable.
*Sometime due to non-lenier characteristic of magnatic
circuit and the presense of harmonics in the fluxes of un-
excited phases, the algebric sum of induced volage in two
phases may not be equal to the applied voltage.
*if there is a turn to turn fault in any phase winding, the
faulty section will draw comparetively large magnatizing
current which will oppose the magnetic fluxes and will
result a very low induced voltage (tends to zero) in the
faulty phase.
*this test should be performed after demagnaizing the
transformer properly. slightly magnatized transformer (like
after insulation test) can give you an unexpacted and
distorted result of magnetic balance test.

what is the terminal voltage of dc series generator running at rated speed at no load?

7741

---

define as synchronous generator

2218

---

what type of questions are asked and howmwny questions belong this catagory?

2162

---

Sir, plz tell me how droop setting is done in parellel operation od DG set ? please give practical example ?

2183

---

What is Icu and Ics and what is difference b/w them. please tell me how to calculate a size of a copper bar for a system or a breaker... reply on... king.arish@gmail.com would be waiting for a logical answer.

2526

---

What is the difference between a 3 winding and 2 winding Potential Transformer

2339

---

WHAT IS SUBSTATION & ACCORDING TO VOLTAGE HT,EHT SUBSTATION EXPLAIN IT

3221

---

1.why we are using metal oxide gapless block in lightning arrester,2.What is minimum and maximum rating of metal oxide blocks using in india

2024

---

if 6 earth pit value is 1.5 ohm then what should be the number of earth pit to make the value .8 ohm

2327

---

why we setting 95 deg and 105 deg in wti and oti of distibution transformer ? give the reson for that ?

3213

---

why core is useful for a transformer ?and also in its operation ?

2145

---

Why is negative feedback invariably preferred in closed loop system?

2376

---

What is the permissable nutral current of three phase system as per IS standards?

2170

---

I completed my BE EEE degree 2006 .... which license should i apply .... ?????

1778

---

which stabilizer is better ? AVR, Servo Stabilizer, Static stabilizer etc & why explain it

2921

---