Electrical Machines Practice Test 5

1. If the emf from the air gap line is the 3-phase alternator is 440V per phase and armature current is 110 A. The synchronous reactance is?

2. For the below graph depicting the performance of a synchronous motor, coordinates 'x' and 'y' are respectively?
In the ‘V’ curve shown in the above figure for a synchronous motor, the parameter of x and y coordinates are, respectively.

3. Potier method is very accurate due to __________

4. Reactive power flow in synchronous machine can be controlled by __________

5. Squirrel cage bars placed in the rotor pole faces of a 3-phase alternator help in reducing hunting.

I. above synchronous speed
II. below synchronous speed
III. at synchronous speed

6. For a three phase synchronous motor, if the following condition is satisfied, it can be said that it is operating at ____________

Vt < Ef-Ia*ra

7. A 315V, 3-phase 400 MVA alternator is running at no load at constant excitations. The most appropriate representation in space domain is?

8. Choose the correct representation for the time phasor below.

9. If the machine size increases, the three phase alternator resistance _______ and synchronous reactance _______

10. If the synchronous machine is loaded from floating conditions, the synchronous motor begins to operate at __________