A synchronous motor is operating with normal excitation. If load is increased the armature current drawn from supply mains also increases. Which of the below mentioned reasons is actually responsible for that:
- Increase in resultant armature voltage
- Increase in back EMF
- Increase in Power Factor
- All of above
Correct answer: 1. Increase in resultant armature voltage
An increase in load on synchronous motor also increases the torque angle of motor. This in turn increases the resultant voltage.
From Ohm’s law:
I(a) = Er/Zs
An increase in resultant voltage results in an increase of armature current I(a). This is the reason when the load is increased on synchronous motor the armature current drawn from supply mains also increases.