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Lecture#10: Storey: Electrical & Electronic Systems © Pearson Education Limited 2004

Induction motors are an important form of AC motor where current is induced in the rotor by transformer action rather than using slip rings. There are two main types of induction motor: squirrel cage and slip ring. Induction motors work by creating a rotating magnetic field from three phases that induces current in the rotor, causing it to turn slightly slower than the magnetic field.

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89 views9 pages

Lecture#10: Storey: Electrical & Electronic Systems © Pearson Education Limited 2004

Induction motors are an important form of AC motor where current is induced in the rotor by transformer action rather than using slip rings. There are two main types of induction motor: squirrel cage and slip ring. Induction motors work by creating a rotating magnetic field from three phases that induces current in the rotor, causing it to turn slightly slower than the magnetic field.

Uploaded by

Hassnain Massid
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Lecture#10

Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 23.1
Induction motors

 These are perhaps the most important form of AC


motor
 Rather than use slip rings to pass current to the field
coils in the rotor, current is induced in the rotor by
transformer action
 The stator is similar to that in a synchronous motor
 The rotor is simply a set of parallel conductors shorted
together at either end by two conducting rings

Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 23.2
Induction motors

 Working of induction motor is described using the


following link:

https://www.youtube.com/watch?v=LtJoJBUSe28&pbjreload=10

Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 23.3
Types of Induction Motor

 There are two types of induction motor:


– Squirrel cage induction motor

– Slip ring induction motor

 Following link explains the difference between the


two:
https://www.youtube.com/watch?v=JPn5Ou-N0b0

Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 23.4
 A squirrel-cage induction motor

Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 23.5
 In a three-phase induction motor the three phases
produce a rotating magnetic field (as in a three-phase
synchronous motor)
– a stationary conductor will see a varying magnetic field
and this will induce a current
– current is induced in the field coils in the same way
that current is induced in the secondary of a
transformer
– this current turns the rotor into an electromagnet which
is dragged around by the rotating magnetic field
– the rotor always goes slightly slower than the magnetic
field – this is the slip of the motor
Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 23.6
Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 23.7
Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 23.8
Key Points
 Electrical machines include both generators and motors
 Motors can usually function as generators, and vice versa
 Electrical machines can be divided into AC and DC forms
 The rotation of a coil in a uniform magnetic field produces a
sinusoidal e.m.f. This is the basis of an AC generator
 A commutator can be used to produce a DC generator
 The magnetic field in an electrical machine is normally
produced electrically using field coils
 DC motors are often similar in form to DC generators
 Some forms of AC generator can also be used as motors
 The most widely used form of AC motor is the induction
motor
Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 23.9

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