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

can we use ZNyn11 transformer instead of Dyn11 transformer in distribution for effectively eliminating harmonics from the industrial loads.

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2 Answers  

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1 Answers  

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super position theorem is applicable to

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sir& friends i want the collection of recent quetions asked in interview of top most companies please send me on my email san.jsr@hotmail.com

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why is a avtomatic voltage regulator used for?

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4 Answers