Answer / hemanshu

beacause carbon contact resistance is too low 0.7 ohm. so its use for exitation of motor & generator.

Answer / kawsar ahmed

We use carbon brush with commutator and slip ring, because carbon has negative coefficient of heat. That means when heat increase carbon brush resistance do not increase.
Another reason is carbon friction loss is less then other element.

Answer / ramesh

Brushes are used in Exciter to facilitate current in
revolving rotor where Field winding is placed. In generators
for Rotor earth fault and as earth to remove any static
current induced in the rotor.

Answer / raul

brushes r the means of supplying the direct current from
the commutator to the external load ........n the contact
resistance is an important factor which plays an important
role. in dc generators, carbon brushes also helps in
improving commutation

Answer / sreeknp

normally brushes are of carbon it is a semiconductor its
resistance decreases with temperature, then self lubricant
this is the reason

in HVDC transmission system ,monopolar link has one conductor usually a negative polarity and use ground or sea return ?through negative polarity we could pass electricity or not yes means how it is possible

1 Answers   Gyana, NNN,

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hi i m going to attend bhel interview on 22nd sep 2008 for ET(electrical engineering).pls guide me how to prepare for the interview.i am a fresher.

1 Answers   Bhel,

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redundant connection in contactor?

0 Answers   Emerson,

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On a 6 KVA UPS we have to provide a DC MCB for Battery bank of 16 nos (12 V 42 AH). What Shall be the current rating of DC MCB ?

0 Answers   TNEB Tamil Nadu Electricity Board,

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why occ characteristics curve in not tracing back when we are bringing back the rhoestat?

0 Answers  

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What are operating procudures & Safety precautions to be observed while operating OLTC in manual mode ?

0 Answers   NTPC,

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what is the working principle of ceiling fan and table fan?

10 Answers   ABC, Tata Steel Limited,

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What is the restart inhabit setting in ABB spam150c relay (Motor protection relay)

0 Answers  

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Please tell me if you are electrical engineer,and you are appointed for the maintainance of Electrical Power plant,then which parts of the plant deal with you.Also tell how these parts/components work.

1 Answers  

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Why in Digital Megger for finding Insulation resistance,-ve is applied to core or conductor and +ve is applied to ground.

1 Answers   ACC,

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Why transformer, generator, ups rating kva?

2 Answers  

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can you check the current and voltage of a 12 V battery by a digital multimeter in this fashion that apply the digital multimeter across the battery terminals directly ? say yes or no ... i sais yes ........... is this true or false ? plzz tell me and also explain ........ plzz thanks

4 Answers  

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