what is the MNA in case of d.c. machin?
whaty is the importance of it?
hoe it affect the brush position?
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Answer Posted / shekar
MNA stands for Magnetic nuetral axis. It is an imaginary
line perpendicular to magnetic lines and passing exactly at
the centre of magnetic field. The emf induced at MNA will
be zero as the conductors will not cut any flux at MNA. At
MNA the conductors will be parallel to magnetic lines.
Hence brushes are located at MNA to collect current. During
armature reaction the MNA shifts in the direction of
rotation of generator. So the brushes should be shifted to
new position of MNA to avoid sparking.
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