Master AC Electrical Machines: Online Quizzes and Learning Resources

Question 1

In a 3-phase induction motor, the rotor speed is always:

Accepted Answer

Less than the synchronous speed (due to slip)

Answer

Equal to the synchronous speed

Answer

Greater than the synchronous speed

Answer

Unpredictable

Question 2

The power factor of an AC machine is defined as the ratio of:

Accepted Answer

Real power to apparent power

Answer

Apparent power to reactive power

Answer

Real power to reactive power

Answer

Reactive power to real power

Question 3

The torque-speed curve of an induction motor is:

Accepted Answer

Non-linear and has a maximum (due to slip)

Answer

Linear and has a maximum

Answer

Non-linear and has no maximum

Answer

Linear and has no maximum

Question 4

The efficiency of an AC machine is:

Accepted Answer

The ratio of output power to input power, expressed as a percentage

Answer

The ratio of input power to output power

Answer

The difference between input and output power

Answer

The product of input and output power

Question 5

Which of the following methods is used to start a synchronous motor?

Accepted Answer

Damper winding (squirrel cage)

Answer

Squirrel cage (used for induction motors)

Answer

Slip ring (used for wound rotor motors)

Answer

Wound rotor (used for induction motors)

Question 6

The armature reaction in an AC machine is caused by:

Accepted Answer

The interaction between stator and rotor magnetic fields, resulting in a distortion of the flux distribution

Answer

The mechanical load on the machine

Answer

The electrical resistance of the windings

Question 7

The equivalent circuit of an AC machine includes:

Accepted Answer

Resistance, inductance, and capacitance (to represent the electrical characteristics of the machine)

Answer

Inductance and capacitance only

Answer

Resistance and inductance only

Question 8

Which of the following is **not** a type of AC machine?

Accepted Answer

DC motor

Answer

Induction motor

Answer

Stepper motor

Answer

Synchronous motor

Question 9

What is the primary advantage of using a squirrel-cage induction motor?

Accepted Answer

Simple and rugged construction

Answer

Variable speed operation

Answer

High efficiency

Question 10

Which of the following is the function of the damper winding in a synchronous generator?

Accepted Answer

To reduce oscillations during transient conditions

Answer

To enhance starting torque

Answer

To improve voltage regulation

Answer

To increase output power

Question 11

What is the main purpose of a slip ring in an AC motor?

Accepted Answer

To transfer electrical power to the rotor

Answer

To reduce noise

Answer

To provide mechanical support

Answer

To regulate speed

Question 12

Which of the following factors does **not** affect the synchronous speed of an AC motor?

Accepted Answer

Load torque

Answer

Rotor inertia

Answer

Supply frequency

Answer

Number of poles

Question 13

What is the significance of the power factor in AC machines?

Accepted Answer

It represents the ratio of real power to apparent power

Answer

It determines the starting torque

Answer

It indicates the efficiency of the machine

Question 14

Identify the type of machine that is NOT classified as an AC machine.

Accepted Answer

DC Machine

Answer

Synchronous Machine

Answer

Induction Machine

Answer

Brushless DC Machine

Question 15

Which type of AC machine exhibits the characteristic of self-starting?

Accepted Answer

Induction Machine

Answer

Stepper Motor

Answer

DC Machine

Answer

Synchronous Machine

Question 16

Which factor primarily influences the speed of a synchronous machine?

Accepted Answer

Frequency of AC supply

Answer

Rotor resistance

Answer

Load torque

Answer

Number of poles

Question 17

In a synchronous machine, what is the primary function of a damper winding?

Accepted Answer

Damping oscillations

Answer

Voltage regulation

Answer

Loss reduction

Answer

Starting torque improvement

Question 18

Which of the following is NOT a type of AC electrical machine?

Accepted Answer

DC Motor

Answer

Stepper Motor

Answer

Induction Motor

Answer

Synchronous Motor

Question 19

What is the primary function of the stator in an AC electrical machine?

Accepted Answer

To generate a rotating magnetic field

Answer

To house the permanent magnets

Answer

To carry the armature windings

Answer

To convert electrical energy to mechanical energy

Question 20

Which type of AC electrical machine has the ability to start without an external starting mechanism?

Accepted Answer

Induction Motor

Answer

Synchronous Motor

Answer

Stepper Motor

Answer

DC Motor

Question 21

What is the primary purpose of slip in an induction motor?

Accepted Answer

To generate torque

Answer

To reduce efficiency

Answer

To increase speed

Answer

To prevent overheating

Question 22

What is the key difference between a salient-pole and a non-salient-pole synchronous motor?

Accepted Answer

Rotor construction

Answer

Power factor

Answer

Stator construction

Question 23

Which type of AC motor is most suitable for applications requiring high starting torque?

Accepted Answer

Wound-rotor induction motor

Answer

Synchronous motor

Answer

Squirrel-cage induction motor

Question 24

What is the primary function of a damper winding in a synchronous motor?

Accepted Answer

To damp out oscillations and improve stability

Answer

To increase efficiency

Answer

To reduce noise

Answer

To improve starting torque

Question 25

What is a major advantage of AC electrical machines compared to DC machines?

Accepted Answer

Reduced maintenance and higher efficiency

Answer

Lower cost

Answer

Smaller size

Answer

Wider speed range