Answer / tareq harb

There are 3 types of excitation systems:
AREP, PMG & Self excitation.

in self excitation the AVR (Automatic Voltage Regulator)
takes its power directly from the out put terminals of the
generator, the main disadvantage of this method is that
when the generator output volatage drops the feeding to AVR
will be insufficient. suppose SHORT CKT fault takes place
on generator terminals as a result the output voltage will
drop too much & AVR shuts down directly with out feeding
this short CKT, if running on island mode (load sharing
mode) the hole system will trip.

But in PMG excitation system, PMG will feed AVR with the
same power nevertheless out put volatge, in case of short
ckt PMG alternator can supply 3 times its rated current for
10 seconds giving enough time for generator breaker to trip
eliminating the short ckt with out affecting the system.

as we see the main advange of PMG ALTERNATORS is its
enhanced immunity against short ckts.

Self excited systems is preferable in single mode operation
as it is cheaper & shorter prime movers.

PMG is strongly recommended in island mode operation.

Answer / j.c.das

PMG or Permanent Magnet Generator are used in brushless
excitation system. It is advantageous from the maintenance
point of view. It doesn't employ carbon brushes as it does
not have a commutator and so no regular wear and tear as in
carbon brushes.

what is dol starter

1 Answers  

---

What core magnetic balance test of transformer? How to do this test in a three phase Star star (star-LV, star-HV) transformer? How to measure and where to measure?

1 Answers   Alstom,

---

principle of power export and import in captive power plant.Is it depends upon voltage,current or frequency?Plz explain briefly.

1 Answers  

---

1 HP = how many Kva

5 Answers  

---

Hi to u all : Friends: Why when operate on 2 phase welding machine the power metr goes reverse ?? the meter is god on other loads. thanks

2 Answers   Gedco,

---

What kind of maintenance is conducted for Transformer

1 Answers   Gulf, UB Engineering,

---

how much current capacity 250 amp. mccb please tell me about whats are the reasons to trip 2 or 3 times in a night. and what are the steps to short out this problem

1 Answers   Havells,

---

Why neutral wire is heating in symmetric single phase distribution of three phase power supply?

2 Answers  

---

Is there possible to Test Transformer for Overfluxing Capability. Or is there any firm who does Overfluxing Test on Transformer?

1 Answers  

---

how can tell us the AC indoor or outdoor which Tr and formulls

1 Answers   Mukand,

---

what is the minimum (Common factor) insulatin resistance of the following a, 4mm sq wire b, cable from 50 mm sq to 800mm sq

1 Answers  

---

My energy meter ratio is -/110/root 3,1A and connected line CT is 100/1,PT is 11kv/110 so what is the MF for meter

1 Answers   Apollo,

---