Question

When the excitation voltage is increased from 1 to 1.3 pu of a 3-phase synchronous motor. Then load angle for the constant power operation ________

(a) must be decreased

(b) can also be increased

(c) increased

(d) decreased

I have been asked this question by my college professor while I was bunking the class.

I'm obligated to ask this question of Power Factor Correction by Synchronous Motors topic in section Synchronous Motors of Electrical Machines

Answer 1

The correct answer is (a) must be decreased

To elaborate: ‘Ef*sinδ’ is to be maintained constant. so if excitation voltage increases then the load angle must decrease.