How the neutral position of brush is located in DC machine?

The ends of each coil are connected to a commutator segment. The commutator consists of insulated copper segments mounted on an insulated tube. Two brushes are pressed to the commutator to permit current flow. The brushes are placed in the neutral zone, where the magnetic field is close to zero, to reduce arcing.

What is armature reaction in DC machines?

Armature reaction is the effect on the main field flux of that flux set up by the currents in the armature winding. The effect is the same for both lap- and wave-wound machines. 3.7 shows the two main poles of a d.c. generator and the distribution of the magnetic flux which crosses the airgap and enters the armature.

What is MNA and GNA?

MNA (Magnetic Neutral Axis) may be defined as the axis along which no emf is generated in the armature conductors as they move parallel to the flux lines. GNA (Geometrical Neutral Axis) may be defined as the axis which is perpendicular to the stator field axis.

How do you reduce the back emf of a DC motor?

To avoid this problem, take the effect of back-EMF into consideration in system design. Motors do have a blowback voltage, a back-EMF that is usually addressed by adding a reverse-biased fast diode, sometimes in addition to a capacitor, across the motor’s supply wires.

What is a magnetic neutral axis in DC machines?

the Magnetic Neutral Axis is the angle at which the conductors of the armature are equidistant from the North and South poles of the field windings, where electromagnetic force is equal in both directions.

Which is the geometric neutral axis ( GNA )?

Geometric neutral axis (GNA) is the axis that bisects the angle between the centerline of adjacent poles. It is the axis of symmetry between two adjacent poles. Consider the armature winding alone. The armature conductors to the left of GNA carry the current inwards (+) and right of G.N.A. carry current in an outward direction (-).

Which is the neutral axis of the armature?

The geometrical neutral axis (GNA) is the axis that bisects the angle between the center line of adjacent poles. The magnetic neutral axis (MNA) is the axis drawn perpendicular to the mean direction of the flux passing through the center of the armature.

How are the brushes of a DC machine connected?

The brushes of dc machines are connected along the magnetic neutral axis so this axis is also known as the commutation axis since the direction of armature current revered along this axis. In this given below the figure, you can see that a dc generator of 2 poles.