Losses and Efficiency – Part 2

Consider the following statements regarding efficiency of electrical machines:
(i) efficiency should be calculated by measuring output and input
(ii) efficiency is maximum when constant losses = variable losses
(iii) electrical machines are designed to have maximum efficiency at full load
(iv) electrical machines are designed to have maximum efficiency at near about full load
(v) efficiency should be calculated by measuring their losses
(vi) efficiency is maximum when constant losses = x times of (variable losses)
Which of the above statements are correct?

No load rotational losses in electrical machine consists of _____________

In an induction motor, which of the following is correct:

Which of the given losses are directly proportional to square of speed?

The usual lamination thickness selected to minimize the eddy current loss in rotor is __________

A consideration of the power losses in electrical machines is essential for which of the following reasons?

For the same rating machines, which of the following statement is correct regarding the efficiency (η)?

Which of the following statements are correct regarding brush contact losses?

In rotating electrical machines, when the armature rotates, there are continuous magnetic reversals and power required for their reversals is called ____________

What percentage of the rated output for DC machine and synchronous machine is taken as stray load losses respectively?

The electromechanical energy conversion devices used in power systems are never operated to deliver maximum power output, because at maximum power output, _____________

The pole shoes in DC and synchronous machines are laminated to reduce ________

To determine the efficiency of the machine, direct load test is not advantageous because of which of the following reasons?