Passive Electronic Components - Inductors.

1
Passive ComponentsInductors

• CEC

2
Contents

• Introduction
• Inductor Types.
• Fixed Inductors.
• Variable Inductors.
• Working Principle.
• Applications.

3
Inductors

• Passive component, exhibits reactance.
• Back EMF generated opposes change in current.
• Inductance measured in Henry.
• Specifications include inductance, current rating
  and tolerance.
• Important characteristics temperature
  coefficient of inductance, Q-factor, working
  frequency range, stability, dc resistance of
  windings etc.

4
Inductors

• Can be classified based on the type of core used.
• Air Core Inductors, Iron Core Inductors, Ferrite
  Core Inductors, Powder Core Inductors etc.
• Transformers, Chokes Intermediate Frequency
  Transformers (IFT) etc.
• Transformer action based on mutual induction.

5
Inductor Types

Inductors
Air Core
Iron Core
Ferrite Core
Powder Core
Fixed Inductors
Variable Inductors
Antenna Coils
Up/DownTransformer
IFT
RF Transformer
Autotransformer
Chokes
Oscillator Coils
Power Transformer
AF Transformer
6
Inductor Colour Coding

7
Inductor Colour Coding

Exercise Colour Code a 680 µH 10 Inductor.
8
Air Core Inductors

• Thin copper wire wound over thick
  cardboard/plastic (former).
• Low value of inductance.
• Suitable for radio frequency applications.

9
Iron Core Inductors

• Copper wire wound on a laminated iron core.
• Laminated core has thin iron sheets pressed
  together and insulated, minimises eddy current
  losses.
• For audio frequency applications.

10
Ferrite Core Inductors

• Coil wound over ferrite core.
• Core movable in variable type.
• For frequency tuning.

11
Powder Core Inductors

• Powdered iron core.
• Low core losses at a given frequency.
• Low permeability.
• For high frequency applications.

12
Chokes

• RF chokes can block high frequencies, pass lower
  audio frequencies and dc.
• AF choke can block audio and power line
  frequencies, allow dc to pass.
• Variable RF chokes available.

13
Transformers

• Two or more coils, induce energy from one circuit
  to another.
• Works by the principle of mutual induction.
• Can step up/step down voltages.
• Change in current induces a magnetic flux in the
  core.
• Core common for primary and secondary windings.
• Voltage induced in the secondary windings.

14
Transformers

15
Power Transformer

• Step up number of turns in secondary higher
  than in primary.
• Step down - number of turns in secondary lower
  than in primary.
• Step down transformers used in power supplies,
  step up in distribution networks.
• Regulation - ability to maintain rated output
  voltage under load, expressed as percentage.

16
Power Transformer

17

18
Intermediate Frequency Transformer

• Tuned to work at 455 KHz using 40 pF capacitance
  across primary/secondary winding.
• 455 KHz known as intermediate frequency in AM
  radio receivers.
• Permeability tuning.
• Initial adjustment may be required to tune to 455
  KHz.
• Aluminium can enclosure.

19
Intermediate Frequency Transformer

20
Audio Frequency Transformer

• In AF applications for voltage/ current/impedance
  transformation.
• Input transformers couple low impedance source
  (eg microphone) to high impedance circuits (eg
  amplifier).
• Output Transformers match high impedance sources
  (eg amplifier) to low impedance loads (eg
  loud speaker).
• Provides isolation and impedance match.
• Used in public address systems, radio receivers.

21
Audio Transformers

22
Autotransformers

• Electrical transformers with only one winding.
• Three terminals, one variable.
• Auto" means single coil acting alone, not any
  kind of automatic mechanism.
• Portions of the same winding act as both primary
  and secondary windings.
• Smaller, lighter, and cheaper than typical
  dual-winding transformers.
• No electrical isolation between primary and
  secondary circuits.

23
Autotransformer

Rotary Arm
Windings
24
Autotransformer

25
Inductor Testing

• Open circuit By continuity check with Ohmmeter/
  Multimeter.
• Shorted/Partially shorted Found by inspecting
  the high frequency response.
• Partial shorting reduces high frequency roll off.
• Measurement Using LCR/Inductance meter,
  Experimental calculation using
• bridge circuits (Maxwell, Hay, Owens etc.)

26
Inductor Ratings

• Wire gauge and physical size of the coil
• determine the current handling capacity.
• Core material will have a temperature
• dependence.
• Temperature variability due to changes in
• the permeability of the core material with
• temperature.
• Air core inductors most stable, followed
• by iron powder, then ferrites.

27
Inductor Handling and Installation

• Inductors not polarized, may be installed
• in either direction.
• Inductors not generally susceptible to
• static electricity, special precautions not
• required.
• To minimize mechanical stress due to
• lead bending.
• In timing/frequency determining circuits
• to be installed in a mechanically rigid
• fashion.
• Melted beeswax prevent mechanical
• shifting of windings.

28
Thank You