I was reading book Electric Machinery by Chapman and in topic 'Armature reaction ' It is written that
"The magnetic neutral plane is defined as the plane within the machine where the velocity of the rotor wires is exactly parllel to magnetic flux lines ,so that E(induced ) in the conductors in the plane is exactly zero ".
This definition of MNP is very confusing for me because
1.I always consider that velocity of conductors is always perpendicular to magnetic field of stator because velocity is tangential to cylindrical surface and magnetic field is radial to cylindrical surface but after reading this definition I'm not sure whether I had this misconception or I am right?
2.and if velocity and magnetic field is always perpendicular the how such a plane (MNP ) is possible where magnetic field and conductors are parllel?
Best Answer
The actual air gap is smaller this so the field is almost perpendicular to the conductor movement around most of the rotor however at the top and bottom of this rotor there is a area where the direction of rotation is parallel to the magnetic field.
At the top and bottom of this machine the rotor coils are moving horizontally. This means that they are not cutting the flux of the magnetic field so no EMF is induced. The MNA is the plane that cuts both of these points.This means that the MNA runs vertically through this machine.