Armature reaction

The effect of armature flux on the main field flux is called as armature reaction. EMF is induced in the armature conductors when they cut the magnetic field lines. But, there is an axis (or, you may say, a plane) along . The armature reaction : demagnetizes the . What-is-armature-reaction-in-dc-mot.

When we excite the field winding, it produces a flux which links with t. What is armature reaction in DC machine? How to Reduce the effects of armature reaction ? Indian Institute of Technology Madras. Earlier, an expression was derived for the induced emf at the terminals of the armature winding under the influence of motion of the conductors under the field established by field poles.

It actually decreases the main flux by which the generated emf to fall with the increase in load current. Thus as the load increases the armature reaction losses increases and hence the efficiency of the Generator .

In a DC machine, the carbon brushes are always placed at the magnetic neutral axis. In no load condition, the magnetic neutral axis coincides with the geometrical neutral axis. Now, when the machine is loade the armature flux is directed along the inter polar axis (the axis in between the magnetic poles)and is triangular . It demagnetizes or weakens the main flux.

It cross-magnetizes or distorts the . Assuming that the generator is not driving and load. Armature Reaction in a d. So that there is no current in the armature conductors. The distribution of main field flux under this case is as shown in the Fig. The flux is distributed symmetrically with respect to axis called polar axis which is line joining the centres of N and S poles. The iron losses in the teeth and pole shoes are determined by the maximum value of flux density at which they work.

Thus iron losses are observed to be more on load than on no load. As soon as current starts flowing through the armature conductor there is one reverse effect of this current on the main field flux of the alternator (or synchronous generator). Due to the armature reaction the maximum . This reverse effect is referred as armature reaction in alternator or synchronous generator. In other words the effect of armature (stator) flux on the flux .

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. Since armature current depends on the electrical or mechanical load on the machine, armature - reaction effects are therefore . Distortion of Main Field Flux gives rise to three detrimental effects: . The conversion of mechanical energy to the electrical energy in the electric dc motor or . ARMATURE REACTION You will remember that the subject of armature reaction was covered in the previous chapter on dc generators. The reasons for armature reaction and the methods of compensating for its effects are basically the same for dc motors as for dc generators. Figure 2-reiterates for you the distorting effect .