# What is armature reactance?

## What is armature reactance?

Armature Leakage Reactance In an AC electrical machine, the magnetic flux set up by the load current which does not contribute to the useful magnetic flux of the machine is known as leakage flux. This leakage flux sets up a self-induced EMF in the armature winding of the machine.

Is armature reaction present in DC motor?

Armature reaction also occurs in a DC motor just like armature reaction in DC Generator. This is expected because when current flows through the armature conductors of a DC motor, it produces flux (armature flux) which lets on the flux produced by the main poles.

What is armature reaction and commutation of 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. The criterion for good commutation is that it should be sparkless.

### What is armature resistance of DC motor formula?

To calculate the armature resistance, subtract the back e.m.f from the voltage, then divide by the armature current.

What is armature mmf in DC machine?

The armature mmf in a dc machine is stationary with respect to field poles but rotating with respect to armature. In case of a deferentially compounded generator with the increase in load current series field flux opposes the main field flux due to which terminal voltage falls rapidly.

What is synchronous reactance and explain the effect of armature reaction?

Synchronous reactance (Xs): It is the imaginary reactance employed to account for the voltage effects in the armature circuit produced by the actual armature leakage reactance and by the change in the air gap flux caused by the armature reaction.

#### What is armature in DC machine?

The armature of an electric machine is the name historically given to the winding where a voltage is induced and power transfer between electrical and mechanical systems occurs. It is a term used in dc machines and ac synchronous machines. In a dc machine, the armature is the rotating circuit.

What are the effects of armature reaction in dc machines?

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 armature reaction How does it affect the operation of a DC machine?

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).

## Why is armature resistance low in DC motor?

The armature produces a back EMF depending on its speed, which bucks the supply voltage. The armature current then will depend on the difference between the supply voltage and the EMF. So the armature resistance must be low enough to allow sufficient current to flow even with this reduced voltage.

What is armature resistance of DC generator?

Armature Winding resistance is the ohmic resistance of the copper winding wires. A brush is used to provide electrical contact between the stationary contacts and moving parts like commutator or slip rings.

What is MNA and GNA in dc machine?

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

### What is armature reaction and types?

What is Armature Reaction? 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 an armature-reaction. The EMF can be induced within the armature conductors whenever they slash the lines of the magnetic field.

Why does the armature winding possess reactance?

This leakage flux will set up an emf because of self-inductance. This emf is known as reactance emf, which leads the armature current I by 900. Thus, the armature winding is said to possess a leakage reactance XL. The voltage drop due to this reactance is IXL.

What is meant by synchronous reactance?

#### What is armature inductance?

Firstly, the armature inductance of the motor causes the waveform of armature current to be much smoother than the waveform of armature voltage, which in turn means that the torque ripple is much less than might have been feared. From: Electric Motors and Drives (Fifth Edition), 2019.

What is the function of the armature in a DC motor?

The function of an armature is multi-purposed. The main role is to conduct current over the field, thus generating shaft torque within an active machine. The secondary purpose of an armature is to produce Electromotive Force (EMF).

What are the two effects of armature reaction?

Armature reaction has two undesirable effects: First, it distorts the main field. Secondly, it reduces the main field flux or both. When the main field is distorted, then there will be a cross magnetizing effect.

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

1) The armature reaction causes the distortion in main field flux. This can be reduced if the reluctance of the path of the cross-magnetizing field is increased. The armature teeth and air gap at pole tips offer reluctance to armature flux. Thus by increasing length of air gap, the armature reaction effect is reduced.

What is the role of armature reaction in any machine?

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