Answer Posted / rajendra kumar

If a 500 kva, 400 v, 60 hz t/f is to be operated on 50 hz
frequency then how will its KVA rating change?
expl-
kva rating depends upon V*I.
flux is same for both coil,
V1=4.44.N.f.phi
phi=k.V1/f=k.400/60=6.6
phi2/phi1=v1*f2/V1*f1=50/60=0.833
phi2=phi*0.833
V2 (sencondry side)=4.44 N2.f.phi2(at 50 hz)
=4.44.N2.f1*phi1
i.e no effect on voltage but flus has decreased means current will be decrease by factor 0.833.that is KVA=V*I2=V*I1*0.833 (decreases)

State thevenin’s theorem?

1122

---

List the disadvantages of constant k filters?

1682

---

How to control motor gearbox speed and friquency? If length of cable and dia given, how to measure the voltage drop?

2048

---

Please elaborate th´evenin’s theorem?

1159

---

what is the constructional difference between a power transformer and potentian transformer?

1776

---

iam preparing for rrb section engineer post in electrical branch.suggest the right textbook for my reference.fromwhere i will get the previous q.papers?

2290

---

Anybody know how schematic diagram for reverse power relay? RPR for generator protection

2151

---

Can anybody please refer the best and simple book for about Protection relays and in detail of all its protection ?

1985

---

Write down the design procedure of commutaj.

2146

---

what is the criteria for selecting fuse rating in 1phase, 2phase & 3phase welding sets?

1782

---

i want to run 11kv star connected motor in 6.6kv with delta connected throught inverter, is it possible?

2041

---

Can you any one explain application of buccholz relay operation and pressure relif device operation of power transformer

1872

---

what is the role of energy meter in distribution system ?

1191

---

what is cascade speed control device?and how this device control the speed of motors?

2174

---

what is the stear deltaprinceple?

1891

---