What do you understand by demagnetizing and cross magnetizing effect of armature reaction in a dc machine?

The opposition of armature flux on the main field flux is called armature reaction. This armature reaction has two undesirable effects, either it weakens (reduces) the main field flux called ‘Demagnetising Effect’ or it distorts the main field flux called ‘Cross-magnetising Effect’.

What do you understand by demagnetizing and cross magnetizing effect of armature reaction in a dc machine how the armature reaction is minimized?

Armature reaction in DC Generator | Demagnetization and Cross magnetization. Armature reaction is the effect of magnetic flux produced by the armature current on the distribution of flux under the main poles of a DC generator. demagnetizes or weakens the main field flux(Demagnetization effect)

What are the effects of armature reaction in a dc generator?

The adverse effects of armature reaction: Armature reaction weakens the main flux. In case of a dc generator, weakening of the main flux reduces the generated voltage. Armature reaction distorts the main flux, hence the position of M.N.A. gets shifted (M.N.A. is perpendicular to the flux lines of main field flux).

What is cross magnetizing effect in armature reaction?

The cross magnetizing armature reaction effect is mainly caused by armature conductors which are located under the pole arc. At high loads, this effect of armature reaction may cause excessive flux density in the trailing pole tip (in generator) and leading pole tip (in motor).

What is cross magnetizing?

Cross-magnetisation is the behaviour of machine mag- netic materials in which the main driving magnetomotive force (MMF) is not applied in the geometrically favoured direction of the magnetic component, so that there is some magnetisation of the component across the favoured direction.

What is the demagnetizing effect?

The term demagnetizing field reflects its tendency to act on the magnetization so as to reduce the total magnetic moment. It gives rise to shape anisotropy in ferromagnets with a single magnetic domain and to magnetic domains in larger ferromagnets. (See magnetic hysteresis.)

Which of the following are effect of armature reaction?

Effects of the armature reaction: Cross magnetization (distortion of airgap flux) Therefore, sparking at the brushes. Demagnetization (Reduction of net flux)

What is the effect of armature reaction on the speed vs torque characteristic of a dc shunt motor?

The armature reaction in the motor affects the torque speed characteristics of the motor. Due to the armature reaction in the motor the shape of the torque speed characteristics will changes.

What is meant by demagnetizing effect?

The demagnetizing field, also called the stray field (outside the magnet), is the magnetic field (H-field) generated by the magnetization in a magnet. The term demagnetizing field reflects its tendency to act on the magnetization so as to reduce the total magnetic moment.

What is cross magnetizing effect in alternator?

It has two undesirable effects, either it distorts the main field, or it reduces the main field flux or both. They deteriorate the performance of the machine. When the field gets distorted, it is known as a cross magnetizing effect. And when the field flux gets reduced, it is known as the demagnetizing effect.

What is armature reaction in alternator?

Armature reaction in alternator is defined as the effect of armature flux on the main flux produced by the field poles. When there exists a relative motion between the magnetic flux and armature winding, the armature conductor cuts the field flux. Hence there will be a change in flux linkage in the conductor.

How the effect of cross magnetizing effect is nullified?

Explanation: To neutralize the cross magnetizing effect of armature reaction, a compensating winding is used. The compensating windings consist of a series of coils embedded in slots of the pole faces. Explanation: Armature reaction can be reduced with the help of compensating winding.