CAUSES, EFFECTS AND REMEDIES TO THE EFFECTS OF ARMATURE REACTION IN D.C MACHINES
Oshin, Ola Austin; Fakorede Ebenezer, Adanikin Ariyo, Joseph Ojotu & Oluwasanmi Alonge
Department of Electrical and Computer Engineering,
Elizade University, IIara-mokin, ondo
Email: austin.oshin@elizadeuniversity.edu.ng
ABSTACT
The effect that the magneto-motive force (mmf) produced from the armature winding or the effect that the magneto-motive force (mmf) produced by the armature current will have on the main field flux produced by the field winding or stator winding is called 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. But when the main field flux is reduced as a result of armature reaction then we have what is known as demagnetizing effect. In general, armature reaction distorts the main field distribution in the air gap periphery.It also leads to demagnetization effect in the machine. Demagnetization effects of armature mmf will reduce the total flux per pole. This reduction is about 1 to 5% from no load to full load. This research work studies the effects of armature reaction in D.C machines. Armature demagnetization and armature cross magnetization of DC machines with different number of poles, conductors, armature current at different electrical angles were obtained. Armature demagnetization and armature cross magnetization of DC machines with different number of poles, conductors, armature current at a particular electrical angle were also obtained. Observations revealed that the effects of armature reaction in DC machines with high number of poles are higher than the armature reaction in D.C machines with lower number of poles. However, the armature cross magnetization increase in D.C Generators when the mechanical angle is less than and reduces when the mechanical angle is more than 12. It was established that Armature demagnetization increase as the number of poles increases in D.C Machines. Also, the results show that Armature demagnetization and armature cross magnetization of DC machines increase for a constant mechanical angle.
Keywords: D.C Machines, Armature demagnetization, D.C generators, armature cross magnetization, magneto-motive force, armature reaction, generated E.M.F, terminal voltage
