In DC motor,the field MMF is given by NI.N-no.of field winding turns,I-excitat

In DC motor,the field MMF is given by NI.N-no.of field
winding turns,I-excitation and both are constant.Then how
could the main flux decreases due to armature reaction.

Question Posted / chaitanya

4 Answers
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In DC motor,the field MMF is given by NI.N-no.of field winding turns,I-excitation and both are con..

Answer / vivin

This armature reaction has two effects
i)demagnetising the field flux(The direction of the flux
around armature conductors can be inferred from the fleming
RH rule)
i))Distortion of the field flux becoz it is in diferent
direction withrespect to main field flux.

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In DC motor,the field MMF is given by NI.N-no.of field winding turns,I-excitation and both are con..

Answer / prabhat

this is bcz of demagnetisation effect

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In DC motor,the field MMF is given by NI.N-no.of field winding turns,I-excitation and both are con..

Answer / najib

In the absence of armature current if we imagine the field
mmf then it passes through the air gap without any
distortion.However as soon as there is a flow of armature
current the forst effect that comes into picture is
crossmagnetization provided saturation is neglected.Hence
it can be concluded the if saturation is neglected there is
no demagnetization but only crossmagnetization.In reality
saturation does set in and cause demagnetizationalong with
crossmagnetization.

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In DC motor,the field MMF is given by NI.N-no.of field winding turns,I-excitation and both are con..

Answer / avinash

By Lenz's Law: current in motion will oppose the cause of the motion. The armature current is in motion due to the MMF hence it will oppose (diminish) the MMF.

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