What Is Armature Reaction And Its Effect

  • What Is Armature Reaction And Its Type

Armature reaction— ‘It is defined as the effect of the magnetic field, set up by the armature current, on the main field flux'.
When a generator is connected to the load, then a flow of current is set up in the armature coil. The armature current produced its own magnetic field which acts in a direction perpendicular with the main field, Which is from N-pole to S-pole. In this way, the reaction of both the field is known as armature reaction.
What Is Armature Reaction And Its Effect

⇒It has the following effect.

→ It causes heavy sparking at the commutator.
→ It weakens and distorts the main flux.
→ It weakens the generated e.m.f.

The brushes are placed exactly on the magnetic neutral axis (m.n.a.), in order to minimize the effect of armature reaction. the m.n.a.is the axis which is the right angle to the main field. The effect of armature reaction is to shift them.n.a. round in the direction of the reaction. Therefore, as a remedy, the brushes are advanced in the direction of rotation.

Sometimes, In large machines, it is not possible, because of their frequent load variation. In these machines, interpoles are used. Interpoles are placed Midway between the main poles and are connected in series with the armature coil. The polarity of an Interpole is the same that of the main pole which comes after it in the direction of rotation. An Interpole strengthens the flux produced by the main pole and thus it reduces the armature reaction.

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