What is effect 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.

What is armature reaction and commutation?

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.

Why does armature reaction occur?

The reaction caused by armature magnetomotive force is usually called armature reaction. The effect of armature magnetic field on the main magnetic field will distort the main magnetic field and produce armature reaction: … The armature magnetic field distorts the main magnetic field, half strengthens and half weakens.

Is armature reaction good or bad?

Due to the above two effects of armature mmf, there are many detrimental effects on the Electrical machine. Distortion of Main Field Flux gives rise to three detrimental effects: Rise in Iron Loss, Poor Commutation and Sparking in Carbon Brushes.

How do you fix armature reaction?

3) The effect of armature reaction can be neutralized by use of compensating winding.

  1. It is always placed in series with armature winding.
  2. The armature ampere conductors under pole shoe must be equal to compensating winding ampere conductors which will compensate armature m.m.f. perfectly.

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 in DC?

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. … 3.7 shows the two main poles of a d.c. generator and the distribution of the magnetic flux which crosses the airgap and enters the armature.

What is commutation process?

Commutation in DC machines is the process by which the reversal of current takes place. In DC generator this process is used to convert the induced AC in the conductors to a DC output. In DC motors commutation is used to reverse the directions of DC current before being applied to the coils of the motor.

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What do u mean by 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 is armature reaction drop?

Armature reaction drop is the effect of a magnetic field on the distribution of the flux under main poles of a generator. Since an armature is wound with coils of wire, a magnetic field is set up in the armature whenever a current flows in the coils.

What is armature MMF?

The effects of the magnetomotive force (mmf) caused by the current flow in the armature windings on the air-gap field of direct-current (dc) and synchronous alternating-current (ac) machines. … In dc machines, the armature reaction causes a distorted flux-density distribution in the air gap.

What are components of armature reaction?

Armature Components. An armature can be designed with the number of components namely the core, the winding, the commutator, & the shaft.

What is armature reaction in DC machines explain its effects?

The armature reaction is the effect of the armature flux on the main flux. In case of a DC motor the resultant flux is strengthened at the leading pole and weakened at the trailing pole tips.

What is back emf in DC motor?

When the armature of the DC motor rotates under the influence of driving torque, the armature of the conductors moves through a magnetic field inducing an emf in them. The induced emf is in the opposite direction to the applied voltage and is known as the back emf.

What is armature flux?

Armature flux is produced due to the current flowing in armature conductors. Now, if we place another winding in close proximity of the armature winding and if it carries the same current but in the opposite direction as that of the armature current, then this will nullify the armature field.

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How does Interpole reduce armature reaction?

Interpoles are wired in series with the armature. Any changes in the armature current due to armature reactance, loading, or self-inductance pass through the interpole windings. This creates a changing magnetic field equal to and opposite that of the armature, thereby cancelling the effect.

What is difference between armature and rotor?

It is located inside the stator and its objective is to rotate so that in turn the motor shaft or generator rotates. So basically, the rotor consists of a field magnet which rotates while the rotor remains stationary and on the other hand the armature carries current and is stationary and part of the stator.

What is armature inductance?

Armature inductance — Armature inductance Inductance of the conducting portion of the motor. If you do not have information about this inductance, set the value of this parameter to a small, nonzero number.

How does armature rotate?

The armature is mounted on bearings and is free to rotate. It is mounted in the magnetic field produced by permanent magnets or current passing through coils of wire, which are called the field coils. When a current passes through the armature coil, forces act on the coil and result in rotation.

What is the working principle of DC generator?

A DC generator operates on the principle of Faraday’s laws of electromagnetic induction. According to Faraday’s law, whenever a conductor is placed in a fluctuating magnetic field (or when a conductor is moved in a magnetic field) an EMF is induced in the conductor.

What is bad commutation?

A machine is said to have poor or bad commutation if there is sparking at the brushes and commutator surface . the bad commutation may be caused by mechanical or electrical conditions. The mechanical conditions include uneven commutator surface non uniform brush pressure, vibration of brushes in the brush holders etc.

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How many types of commutation are there?

Three types of commutation are identified: i) Voltage commutation, ii) Current commutation and iii) Load commutation. In a voltage commutated thyristor circuit a voltage source is impressed across the SCR to be turned off, mostly by an auxiliary SCR.

What is commutation and its types?

The process used for turning off a thyristor is called commutation. By the commutation process, the thyristor operating mode is changed from forward conducting mode to forward blocking mode. … The commutation techniques of thyristors are classified into two types: Natural Commutation. Forced Commutation.

What is meant by back EMF?

Counter-electromotive force (counter EMF, CEMF), also known as back electromotive force (back EMF), is the electromotive force (voltage) that opposes the change in current which induced it. CEMF is the EMF caused by magnetic induction (see Faraday’s law of induction, electromagnetic induction, Lenz’s law).

What is armature reaction and their power factor?

The effect of Armature (stator) flux on the flux produced by the rotor field poles is called Armature Reaction. The power factor can be defined as the cosine of the angle between the armature phase current and the induced EMF in the armature conductor in that phase. …

What is the function of commutator?

The function of commutator ring in an electric motor is to reverse the direction of current flowing through the coil every time coil just passes the vertical position during a revolution. Hence as the direction of the current is reversed, the torque is changed in the direction.