Armature Reaction in an Alternator and Power Factor

Armature reaction is the effect of the magnetic field produced by the current flowing in the armature winding of an alternator on the main magnetic field produced by the field winding. The interaction of these two fields can cause changes in the voltage, current, and power factor of the alternator.

Effect of Armature Reaction on Power Factor

When the armature reaction produces magnetization of the main field, the power factor of the alternator is affected. The power factor is the ratio of the real power (kW) to the apparent power (kVA) of the alternator. It is a measure of the efficiency of the alternator in converting electrical power to useful work.

In this case, the armature reaction causes the voltage and current waveforms to be distorted, resulting in a lagging power factor. This means that the current lags behind the voltage, reducing the efficiency of the alternator. The lagging power factor can cause problems in electrical systems, such as increased losses, reduced voltage regulation, and reduced system stability.

Therefore, the correct answer is option 'A' - zero, lagging load. When the armature reaction produces magnetization of the main field, the power factor of the alternator is zero with a lagging load. This means that the alternator is not producing any useful work, and the power is dissipated as heat in the windings and other components of the electrical system.

Conclusion

Armature reaction is an important phenomenon that affects the performance of an alternator. It can cause changes in voltage, current, and power factor, which can have significant impacts on the efficiency and stability of the electrical system. It is important to understand the effects of armature reaction and take appropriate measures to mitigate them, such as using compensating windings, adjusting the excitation system, or changing the load conditions.