Answer / nagendra murthy

any DC motor or generator will need to have a commutator. A
commutator is a device used to change the direction of
current flow through the motor. The reason a cummutator is
needed is because a DC current in a magnetic field can only
turn the motor through 180 degrees, after which the force
will cause the motor to return to a fixed position. In order
to make the force turn the motor the current needs to be
changed every 180 degrees so that the force will act in the
opposite direction, spinning the motor around. This is
achieved using a commutator. The commutator is normally a
device which brushes against terminals in the motor. As the
motor turns the terminals in contact with the brushes
change, and so does the current.

Answer / paragbajpai

1.carbon brushes are used as it is having high resistance so
that time constant will be reduced that means commutation
will be improved.
2. it has self relieving property

Answer / k.prakashchandra

1.A good conductor 2.has desired hardness 3 can be easily
Reshaped 4.cheap 5. easily available 5. does not corrode 6.
cleaning is easy 7.weather resistant 8 not inflammable etc

Answer / sarath k

the carbon brushes are used as commutators because of resistance commutation and the carbon has self polishing property

Answer / satheeshkumar

Only The carbon having possessing the negative temperature coefficient This is the main reason using for commutation porpose (The ratio of increasing resistance per degree centigrade o the resistance at 0 degree centigrade) dippend the carbon inverse action must take place

Answer / gautam

carbon acha nahin hota hai

how to calculate of which rating transformer should be selected? take any example

2 Answers  

WHAT IS ELECTRICAL MAINTAINTENCE ?

0 Answers  

why Current is lead 90 degree and voltage is lag 90 degree in a capacitor.? why Current is lag 90 degree and voltage is lead 90 degree in an inductor.?

0 Answers  

how we can come to know that motor winding resistance which showing by DMM is right or wrong???is there any chart or something that we will compare & check???

0 Answers  

What is the difference between LT CT & HT CT?Can we use indoor type transformer as an outdoor type or vice versa?

2 Answers   Bhel,

Why does the adjacent zone of protection overlap?

0 Answers  

How to do bus bar short circuit calculation for 230KV/11kv, 60 MVA Substation?

0 Answers   ABB,

what is difference between tension tower and suspension tower?

8 Answers  

How to Preparation of online test

0 Answers  

what is diversity factor ? plzzzzzz describe me

1 Answers  

advantage of using 110v than 230v

1 Answers   NTPC,

how to calculate size of cable from motor current given and how to calculate full load current of a induction motor.

3 Answers   Aarti Steels,