Answer / madhusudhan

inorder to produce constant magneticfield we required to
apply D.C rather than A.C. which gives variable magnetic
field

Answer / shantanu mishra

The DC current also called field current or excitation
current is given to produce magnetic field in which rotor of
the generator rotates and produces EMF. the EMF can be
varied by regulating field current.

Answer / mahesh

we need a rotational magnetic field of sine wave for the
emf to be induced . if dc is given, the field that is
produced in the air gap is almost a sine wave with constant
magnitude. for ac excitation the air gap flux is not a sine
wave .

Answer / u.vijay bhaskar reddy

for producing constant flux on the rotor

Answer / nagarjunacharya

to produce emf in the stator either we should apply
alternating flux or dynamic(rotating) conductor.as already
we are rotating rotar by prime mover ,wewe have to apply.

Answer / venkatrao chowdary

the dc current produce constant magnetic field.when rotor
conductors are rotated this conductors cuts the magnetic
lines of flux than emf is induced.this emf is called
dynamically induced emf.when ac is given to the alternater
it induces statically induced emf.the operation of
alternater we need dynamically induced emf.so ac is not
given to the alternater.

Answer / u.v.subhashreddy

alternator is an speeed machine. the dc current gives
exication current is given to produce a magnetic field so
giving d.c supply to field of an alternator.

Answer / y.srinath

dynamically induced e.m.f requires fixed polarity& magnetic flux .if we given a.c to field the polarity of a particular pole is not fixed .if one pole behaves as north pole for +ve half cycle & same behaves as north pole for negative half cycle to.that's why we are using d.c supply for alternator.

Answer / b madhu sudhan reddy

alternator is a constant speed machine.i.e it always runs
at synchronus speed.so,for producing constant speed we
require constant excitation.so,for the constant excitation
we require constant supplly.i.e d.c supply

Answer / pravallika

for magnetising poles in rotor

How do you select a cable size(Cu & Al) for a particular load?

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what is the diffrence between kav and kvar?

5 Answers  

Energy metering: On the property I am renting, the supply voltage is 2 x 110 volts. These 2 x phases enter a energy meter which then exit the meter to over head lines to my house. Question 1. The meter is single phase 240 volts but is being used as 2 x phase(2 x 110volt), is this acceptable? if not, please give me the reasons. The meter details are as follows: 60Hz 15amp Imax 100 amp Kd 3,6 Wh/R 1 fase 3 hilos Model FX 231. I think it was manufactured in Brasil From this meter, the cables run along over head aluminum conductors,I estimate the cross sectional area to be 25mm diameter, but the neutral is only about 10mm square diameter, which cover a distance of 170 meters and then terminate with an underground cable of 65 meter length, total length = 235 meters. There must be a huge voltage drop over this length. This line is protected with 2 x 200 amp aluminum fuses after the meter, there is no main switch in the distribution board. These 2 phases connect directly onto 2 busbars. Surely the neutral should be the same size as the conductors if not more? Question2. What are your thoughts about this installation, should there be better protection, is the neutral too small? During the night, the lights dim then brighten all the time, this cannot be good for my electrical appliances. In my home, I only have a small electric geyser and fridge, my stove works off gas. But when i use other appliances like the washing machine or microwave oven, the light dim. The internal wiring of this house is done with solid hard drawn copper wires and of course, they have to be under rated. I am a retired electrician by trade, but not on the metering and over head mains side, my experience is on the factory maintenance side of things. Your expertise on these matters will be greatly appreciated. Please inform me how to rectify or make any improvements Kind regards, my power bill is very expensive, so I need to know how to bring it lower. Kind regards, Brian

1 Answers  

Why generally the transformer primary is connected in star & secondary in delta

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What is IDMT relay how it works.

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how does relay works?

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diff. between tension mode & speed mode

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