It is smaller in size

It provides a constant torque and is more efficient

It requires less wiring

It operates only at low voltages

$$45^\circ$$

$$60^\circ$$

$$90^\circ$$

$$120^\circ$$

To supply electrical power

To create a magnetic field

To rotate and deliver mechanical output

To regulate voltage

Wound rotor

Squirrel cage rotor

Permanent magnet rotor

Salient pole rotor

It has windings connected to slip rings

It consists of bars short-circuited by end rings

It uses permanent magnets

It is made entirely of copper wire

The difference between input and output voltage

The difference between synchronous speed and rotor speed

The amount of current lost as heat

The distance the rotor moves per revolution

$$s = \frac{N_s - N_r}{N_s}$$

$$s = \frac{N_r}{N_s}$$

$$s = N_s \times N_r$$

$$s = N_s + N_r$$

0%

2-5%

10-15%

20-25%

The rotor windings

The stator windings supplied with three-phase current

Permanent magnets

The commutator

750 rpm

1000 rpm

1500 rpm

3000 rpm

Simple and robust construction

High starting torque

Low maintenance

Easy speed control

Because of friction losses

Because slip is required to induce current in the rotor

Because the supply voltage is too low

Because the stator is not energised

Hertz (Hz)

Cycles per second (cps)

Revolutions per minute (rpm)

Kilohertz (kHz)

Rotor

Stator

Commutator

Shaft

To cool the motor

To induce current in the rotor and produce torque

To reduce noise

To increase resistance

It decreases

It remains the same

It increases

It becomes zero

Laminated iron core with copper or aluminium bars and end rings

Solid steel cylinder

Wound coils connected to slip rings

Permanent magnets attached to a shaft

The slip decreases

The slip increases

The slip remains constant

The motor stops

$$N_s = \frac{120f}{P}$$

$$N_s = \frac{60f}{P}$$

$$N_s = f \times P$$

$$N_s = \frac{P}{120f}$$