MNA And GNA
When armature conductors cross magnetic field lines an electromagnetic field (EMF) is created. There is an axis or plane where these conductors do not cross the flux lines as they go parallel to them. This axis where armature conductors moving parallel to flux lines do not generate an electromagnetic field (EMF) is known as the Magnetic Neutral Axis (MNA). Because brush placement helps the current in the armature conductors to reverse, brushes are positioned uniformly along the MNA. Conversely, the stator field axis is perpendicular to the Geometrical Neutral Axis (GNA).
Diagram For MNA and GNA(showing Distortion of the main Field Flux due to the armature Flux)
Leading Pole Tip And Trailing Pole Tip
These two describe the locations of the magnetic poles with respect to the armature rotational direction in the context of armature reaction in DC machines.
Leading Pole Tip: This is the pole tip that is ahead of the neutral plane in the direction of rotation. The combined action of the armature reaction and the main field produces a greater magnetic field at the leading pole tip this increasing flux density.
Trailing Pole Tip: In the opposite direction of rotation the trailing pole tip is situated behind the neutral plane. The main field and armature reaction combine to produce a weaker magnetic field which lowers the flux density.
Analyzing the impact of armature reaction on commutation and overall machine performance in DC machines requires an understanding of the positions of the leading and trailing pole tips. With this knowledge engineers may ensure stable operation and build compensating techniques.
Armature Reaction In DC Machines
In DC machines the term armature reaction describes the distortion of the magnetic field brought on by the current flowing through the armature winding. The machine’s overall magnetic field is affected by the magnetic field produced by the armature as it carries electricity. The machine’s performance especially in terms of voltage regulation & commutation may be impacted by this interaction which may result in changes to the neutral plane. For DC machines to operate steadily and effectively the armature reaction needs to be taken into account and compensated for by engineers.
In a DC machine, there are two types of magnetic forces present one is the armature flux & the main field flux. When the armature flux affects the main field flux it is called an armature reaction.
Table of Content
- MNA And GNA
- Cases Armature reaction
- How to reduce Armature Reaction
- Effects of Armature Reaction
- Applications of Armature Reaction