Answer Posted / iamdon

No.....AC voltage cannt be used in field winding of rotor
of synchronous machines for following reasons....

1)AC produce poles on rotor whose strength is varying
sinusoidally.It is undesirable because the magnetic locking
between two fields in this case are not achieved troughout
the cycle.At current zero of AC there is no locking at
all.So synchronism will be lost.

2)Field winding is designed for DC. It has higher
resistance.According to Lenz law emf is induced in field
winding.so current flowing through through winding will be
very low.Pole strength is very weak.

excitation limit of an excitor

2110

---

What is effect of harmonic current (Draw by VFD) on power system/ electrical Equipments ?

2140

---

1) why a dg set shows variation of power factor and load when synchronised with other dgs? 2)Why the load sharing is not become equal in all dgs?. 3)When a dg set will not run on auto start?

2050

---

Explain the advantages and disadvantages of thermal power plant?

1142

---

hii this is ranjith from hyd... i want to know what type of questions they ask in interview...and hw the interview will go..? what subjects thay ask specially for electrical engg students?

2025

---

What fomula is used to calculate: 1. rated frequency withstand voltage, and 2. rated lightning impulse withstand voltage.

1771

---

What is a signal flow graph?

1132

---

Explain how you decide what size of electrical wire do you need?

1188

---

Define maximum demand?

1120

---

What are the disadvantages of thermal power plant?

1156

---

Why is the starting current high in dc motor?

1174

---

what's the simultenous maximum demand (SMD)..what the diffrent MD and SMD?

2621

---

physical identification of HT & LT panel

1727

---

what is the chemical name and formula of refrigarent R-134a.

2340

---

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

2082

---