Sage-Tips

What happens to the direction of the rotation of the armature the direction of the current is reversed?

DirectION of ROTATION If either the direction of the field or the direction of current flow through the armature is reversed, the rotation of the motor will reverse. However, if both of these factors are reversed at the same time, the motor will continue rotating in the same direction.

How the direction of rotation of armature can be changed in DC motor?

The direction of rotation of DC series motor may be reversed by changing the polarity of either field or the armature winding. The direction of the torque and the speed can be reversed by changing the direction of either the field current or armature current by changing the polarity of the DC voltage.

What is armature reaction How does it affect the operation of a DC machine explain through illustration?

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 in DC motors?

In a DC machine, two sources of magnetic fluxes are present; ‘armature flux’ and ‘main field flux’. The effect of armature flux on the main field flux is called “armature reaction”. The armature reaction changes the distribution of the magnetic field, which affects the operation of the machine.

What changes the direction of current flow through the armature loop?

The loop (armature) field is both attracted and repelled by the field from the field poles. After the loop has turned far enough so that its north pole is exactly opposite the south field pole, the brushes advance to the next segments. This changes the direction of current flow through the armature loop.

Why does motor rotate in reverse direction?

In order to reverse the direction of an AC motor, the magnetic fields must be altered to provoke movement in the opposite direction. Since each wire consists of a positive and negative current within the magnetic fields, the flip-flopping of main and starter wires causes the motor to run in reverse rotation.

What is armature reaction?

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.

What will happen to the direction of rotation of a DC shunt motor if armature terminals are reversed?

When both (the direction of the field as well as that of armature current) are reversed the direction of rotation will not change. So in the case of DC shunt motor, if the supply terminals are interchanged, there is no change in the direction of rotation.

How does armature reaction occur?

Why does armature reaction occur?

In other words, the armature reaction represents the impact of the armature flux on the main field flux. The armature field is produced by the armature conductors when current flows through them. And the main field is produced by the magnetic poles. The armature flux causes two effects on the main field flux.

Why does a DC motor produce an armature reaction field?

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. For a motor with the same polarity and direction of rotation as is for the generator, the direction of armature reaction field is reversed.

How does armature reaction cause commutation problem?

The direction of the magnetic neutral axis is shifted with the direction of resultant flux in the case of the generator, and it is opposite to the direction of the resultant flux in the case of the motor. The armature reaction induces flux in the neutral zone, and this flux generates the voltage that causes the commutation problem.

What is the difference between armature and armature reactions in DC generators?

We can conclude that:Armature reaction in a DC generator weakens the flux at leading pole tips and strengthens the flux at trailing pole tips while the armature reaction in a DC motor produces the opposite effect.

What is the armature reaction in a magnetic field?

In other words, the armature reaction represents the impact of the armature flux on the main field flux. The armature field is produced by the armature conductors when current flows through them. And the main field is produced by the magnetic poles.