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

what factors to needed while selecting a MCB and MCCB

3 Answers  

what is difference between isolation and ultra isolation transformer?, what is the method of testing ?

0 Answers  

how step up transformer step up the voltage and what is the reason behind it?

3 Answers  

what is static switch where it can be use?

1 Answers  

what is the meaning of transformer short circuit test?

7 Answers   HZL, L&T,

What is the latest generation of circuit breakers called?

2 Answers   Focus, Oil India,

what is the clearances between phease to phease & phease to earth in 400 kv transmission line?

1 Answers   Lanco,

draw waveform of capacitor or inductor in a d.c ckt(during transient) with zero resistance with it(in series or parallel)also neglect resistance of wire

2 Answers   L&T,

How to select a D.G set for calculated load of 110kW..?

7 Answers   Shakthi Power Systems,

If you know per phase current and phase to phase voltage; what is overall KW of the circuit?

1 Answers   ABC, GAS,

details of oil cell size of Breakdown voltage test of tranformer oil details as per Standardswith mushroom electrodes?

0 Answers  

HI,how to know that the MEGGER which i am using is working properly,reply....thankyou

2 Answers   NTPC,