Professional Electrical Engineering Quiz 2 part 2

A 6-pole lap wound dc generator has 240 armature conductors, a flux of 0.04 Wb per pole and runs at 1,500 rpm. If the armature resistance is 0.8 Ω, determine the current through each conductor.

• 300 A

• 100 A

• 50 A

• 25 A

An air-cored toroidal coil has 450 turns and a mean diameter of 300 mm and a cross-sectional area of 300 mm². Determine the self-inductance of the coil.

• 81 x 10⁻⁴ H

• 1.81 x 10⁻⁴ H

• 0.81 x 10⁻⁴ H

• 0.081 x 10⁻⁴ H

A 4-pole, three-phase 50 Hz induction motor develops a maximum torque of 20 N·m at 1,440 rpm. Obtain the torque exerted by the motor at 5% slip.

• 16.51 N-m

• 17.51 N-m

• 18.51 N-m

• 19.51 N-m

A transformer has negligible resistance and a p.u. reactance of 0.1. What is its voltage regulation on full load with a leading p.f. angle of 30°?

• -10%

• 10%

• 5%

• -5%

In an ac circuit, a low value of KVAR compared with KW indicates

• maximum load current

• low efficiency

• high power factor

• unity power factor

The frequency of the emf in the stator of a 4-pole induction motor is 60 Hz, and that in the rotor is 2 Hz. At what speed is the motor running?

• 1,720 rpm

• 1,740 rpm

• 1,760 rpm

• 1,780 rpm

The voltage across a 50-µF capacitor rises at a constant rate of 10 V/ms. Calculate the current through the capacitor.

• 50 mA

• 500 mA

• 5 mA

• 5 A

Branch circuit larger than ___ amperes shall only supply nonlighting outlet load.

• 15

• 20

• 30

• 50

In a 4-pole dynamo, the flux per pole is 15 mWb. Calculate the maximum emf induced in one of the armature conductors if armature is driven at 600 rpm.

• 0.6 V

• 0.3 V

• 0.94 V

• 0.47 V

How much larger is the rotor reactance of a SCIM at start-up than it is when the motor operates at 5 percent slip?

• 10 times

• 5 times

• 25 times

• 20 times