Pre-Final Examination

A 200-hp, 2200 V, 3-phase star-connected synchronous motor has a synchronous impedance of 0.3 + j3 ohm per phase. Determine the induced emf per phase if the motor works on full load with efficiency of 94% and a power factor of 0.8 leading.

• 1310 V

• 1360 V

• 1469 V

• 1528 V

A 500 V, 50 Hz, single phase synchronous motor develops 20-hp and is operating at pf of 0.8 lagging. Effective resistance of armature is 1 ohm iron and friction losses of amount to 500W. Determine power drawn by the motor from the source.

• 17,288 W

• 20,065 W

• 21,546 W

• 21,564 W

The speed of a synchronous motor connected across a 50 Hz supply is 1000 rpm. Determine the number of poles.

• 4

• 6

• 8

• 10

A single phase synchronous motor gives an output of 9.46 kW at 0.9 pf lagging with 600 V. if stray power loss is 600 W and field losses 700 W, while effective armature resistance is 0.6 ohm, find the efficiency of the synchronous motor

• 74.577 %

• 84.638 %

• 86.180%

• 97.665 %

A lamp gives an average output of 628 lumens. What is its M.S.C.P.?

• 40 Cd

• 45 Cd

• 48 Cd

• 50 Cd

A lamp has luminous intensity of 250 Cd. Calculate the total luminous flux emitted by it.

• 758 lm

• 1000 lm

• 2000 lm

• 3142 lm

1. A light source which radiates lights in all directions has luminous intensity of 100 candela. What is the illumination E in footcandles in a perpendicular working area 10 ft distance below the source?

• 1

• 2

• 2.5

• 3

A light source has an illumination of 100 footcandles, what is the illumination in flux?

• 1,075

• 1,204

• 1,360

• 1,496

In a balanced three phase star connected circuit the line voltage are equal

• and so are the line currents

• but the line currents are unequal

• to the line current

• to the phase voltage

A certain light source produces an illumination of 800 lux on a surface. Find the illumination on that surface if the distance to the light is doubled.

• 100 lux

• 200 lux

• 300 lux

• 400 lux