# What is armature reaction and commutation in DC machine?

## What is armature reaction and commutation in DC machine?

The action of armature flux on the main flux is called armature reaction. In the previous chapter (Sec 1.19), it was hinted that current in the coil is reversed as the coil passes a brush. This phenomenon is termed as commutation.

### What is armature reaction in dc machines?

3.10 Armature reaction in d.c. generators. 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.

How does armature reaction affect commutation?

The armature reaction causes shifting the magnetic neutral axis. Therefore there will be some flux density at brush axis which produces emf in the coil undergoing commutation. This will lead to delayed commutation. Thus the armature reaction at brush axis must be neutralized.

What is the effect of armature reaction of DC machine?

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 do you understand by armature reaction?

Definition of armature reaction : a magnetomotive force set up by the current induced in the armature of a dynamo that results in altering as to both magnitude and direction the flux due to the field magnet.

### What are the types of armature reaction?

Types of Armature-Reaction

• Demagnetization of the stator field.
• The cross magnetization of the stator field.

What is armature reaction?

What is commutation in DC machine?

The commutation in DC machine or more specifically commutation in DC generator is the process in which generated alternating current in the armature winding of a dc machine is converted into direct current after going through the commutator and the stationary brushes.

## How can the armature reaction be reduced in a DC machine?

Reduction Of Effects Of Armature Reaction

1. The armature reaction causes the distortion in main field flux.
2. If reluctance at pole tips is increased it will reduce distorting effect of armature reaction.
3. The effect of armature reaction can be neutralized by use of compensating winding.

### What is armature reaction and types?

Types of Armature-Reaction The armature-reaction is one kind of magnetic field effect which is occurred by the flow of current throughout the armature conductors over the stator magnetic field.

What do you mean by commutation explain?

1 : exchange, trade. 2 : replacement specifically : a substitution of one form of payment or charge for another a commutation by money payment for the exacted service.

What is commutation reaction?

The commutation in DC machine or more specifically commutation in DC generator is the process in which generated alternating current in the armature winding of a dc machine is converted into direct current after going through the commutator and the stationary brushes. It is called commutation period.

## What is an armature reaction in a DC machine?

In a DC machine, two kinds of magnetic fluxes are present; ‘armature flux’ and ‘main field flux’. The effect of armature flux on the main field flux is called as armature reaction.

### What is commutation problem in DC machines?

Commutation problem is not the only problem in DC machines. At heavy loads, the cross magnetizing armature reaction may cause very high flux density in the trailing pole tip in generator action and leading pole tip in the motor action.

What are the adverse effects of armature reactions on DC generators?

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 happens to the armature flux when the machine is loaded?

Now, when the machine is loaded, the armature flux is directed along the inter polar axis (the axis in between the magnetic poles)and is triangular in wave shape. This results an armature current flux directed along the brush axis and causes cross magnetization of the main field.