UPPCL EE :Electrical Machines Quiz 4

In an alternator, the armature winding is kept stationary while the field winding is kept roating for the following reasons:
1) Armature handles very large current and high voltage
2) Armature fabrication, involving deep slots to accommodated large coils, is easy if armature is kept stationary
3) It is easier to cool the stator than the rotor
Which of the above reasons are correct?

The front and cross-sectional view of simple loop alternator is shown in figure. the direction of emf at the instant shown would be

Conductor 2  3  5  6

A synchronous generator connected to infinite bus is supplying half of the maximum power which is 1 pu. Then synchronizing power coefficient is

In the methods of synchronization of the alternator to the busbar, a synchroscope indicate

1. The pointer rotates anticlockwise direction if the machine is running slower

2. The point rotates clockwise if the machine is running fast

3. The point indicates vertically upwards if the speed is correct

Which of the following is correct

A 3ϕ, 50 Hz, 4 pole alternator has a star connected winding with 72 slots and 12 turn per slot. The flux per pole is 0.05wb. The Generated per phase emf is (k_d = 0.956)

Which of the following operating aspects necessitate the computation of Regulation of an alternator?

1) When load is thrown off

2) For designing of an automatic voltage-control equipment

3) For determination of steady-state and transient stability

4) For parallel operation of alternators

In the calculation of voltage regulation in synchronous machines by ZPF method. Triangle formed is ______

Which of the following quantities are considered which measuring synchronous reactance?

i. Armature reaction

ii. Leakage reactive

iii. Power factors

iv. Core saturation

The second-harmonic component of the power P versus load angle δ characteristic of a synchronous machine, operating at a terminal voltage V_t and having the d- and q-axis reactance per phase of X_d and X_q, respectively, is