Subject Title: INDUSTRIAL ELECTRONICS

Subject Code: RTS301T

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1.0 Introduction
2.0 Power Semiconductor devices
3.0 Inverters
4.0 Power supplies
5.0 UPS
6.0 Electromechanical devices
7.0 Handling of Electronic components
 1.0 INTRODUCTION
Linear Electronics:
Linear electronic devices process signals and are mostly designed to operate in the linear
active region unless they are operated as logic gates in which case they are optimized to switch as
fast as possible.
Power Electronics:
Power (electric power), Electronics and Control systems. Power engineering deals with the
static and rotating power equipment for the generation, transmission, and distribution of electric
power

1.1 Linear Electronics Vs Power Electronics

Parameters LINEAR ELECTRONICS POWER ELECTRONICS

Linear electronics deals with the Power electronics deals with

linear relationship between the conversion, control, and conditioning
Definition
current input and the voltage output. of electric power into a desired
electrical output.
In power electronics all devices are In power electronics all devices are
Operating operated in linear or active region operated in switching mode (saturate
region and cut off region)

Semiconductor devices are used as semiconductor devices are used as

Operation amplifier, differentiator, filters, and switches such as in "on" or "off"
Signal generators. states

Power handled milliwatts to watts watts to Mega watts

Power losses are high in linear Power losses are less in power
Power losses electronic components electronics components

NOTES:

2
 Scope of and Application of Power Electronics
1. Commercial applications
Heating Systems Ventilating
Air Conditioners
Central Refrigeration
Lighting, Computers and Office equipment’s
Uninterruptible Power Supplies (UPS)
Elevators, and Emergency Lamps
2. Domestic applications
Cooking Equipment’s,
Lighting, Heating
Air Conditioners
Refrigerators & Freezers
Personal Computers, Entertainment Equipment’s
UPS
3. Aerospace applications
Space shuttle power supply systems
Satellite power systems
Aircraft power systems.
4. Telecommunications
Battery chargers, power supplies (DC and UPS)
Mobile cell phone battery chargers
5. Transportation
Traction control of electric vehicles
Battery chargers for electric vehicles
Electric locomotives
Street cars
Trolley buses
Automobile electronics including engine controls.
6. Utility systems
High voltage DC transmission (HVDC)
Static VAR compensation (SVC)
Alternative energy sources (wind, photovoltaic)
Fuel cells, energy storage systems
Induced draft fans and boiler feed water pump.

NOTES:

3
 Types of power electronic converters:
1. Rectifier (AC to DC converters): These converters convert constant ac voltage to variable dc
output voltage.
2. Choppers (DC to DC converters): Dc chopper converts fixed dc voltage to a controllable dc
output voltage.
3. Inverters (DC to AC converters): An inverter convert’s fixed dc voltage to a variable ac output
voltage.
4. Cycloconverter (AC to AC converters): These circuits convert input power at one frequency to
output power at a different frequency through one stage conversion.

2.0 POWER SEMICONDUCTOR DEVICES

2.1 Introduction
Power electronics is one of the
important branches of electronics and
electrical engineering. It deals with conversion
and control of electric energy.
The power electronic system thus performs
conversion of electric energy. It also controls
the amount of electric energy to be given to the
output.

NOTES:

4
 Power semiconductors employed in power management systems include power switches,
and rectifiers (diodes)
Power semiconductor devices are broadly categorized.
1. Power Diodes
2. Power transistors (BJT)
3. Power MOSFETS.
4. IGBT
5. Thyristors
1. Power Diodes
Power Diodes of largest power rating are required to conduct
several kilo amps of current in the forward direction with very little
power loss while blocking several kilo volts in the reverse direction.
This apparent contradiction in the requirements of a power diode is
resolved by introducing a lightly doped ―drift layer of required
thickness between two heavily doped p and n layer.

Structure of Power Diode

Power diode consists of three layers. The top layer is a heavily doped P+ layer. The middle
layer is lightly doped n– layer and the last layer is a heavily doped n+ layer. The heavily doped p+
layer acts as an anode. The middle layer of lightly doped n– is known as a drift layer.
The Voltage-Current Characteristic of a Diode
When forward biased
The diode begins to conduct current as the voltage across its anode (with respect to its
cathode) is increased. When the voltage approaches the so-called knee voltage, about 1 V for
silicon diodes, a slight increase in voltage causes the current to increase rapidly. This increase in
current can be limited only by resistance connected in series with the diode.

NOTES:

5
 When the diode is reverse-biased
A small amount of current called the reverse leakage current flows as the voltage from
anode to cathode is increased; this simply indicates that a diode has a very high resistance in the
reverse direction. This large resistance characteristic is maintained with increasing reverse voltage
until the reverse breakdown voltage is reached. At breakdown, a diode allows a large current flow
for a small increase in voltage. Again, a current-limiting resistor must be used in series to prevent
destruction of the diode.

Reverse recovery characteristics of the Power diode

ta → time when charge from depletion region is removed.

NOTES:

6
 tb → time when charge from semiconductor region is removed.
tRR – Reverse Recovery Time is the time taken to change the current from ON state to OFF state.
TRR = ta + tb
The ratio of the two parameters ta and tb is known as the softness factor SF.
SOFTNESS FACTOR = tb / ta
Power diodes can be classified as:
1General purpose
diodes. 2 Fast recovery
diodes
3 Schottky Diodes.
1. General purpose diodes:
These diodes have a high reverse recovery time of about 25m s. They are used in low
frequency applications, e.g., line commutated converters etc. Their rating covers a very wide range,
current about 1A to 2000 A or so and voltage 50 V to 5 kV.
2. Fast Recovery diodes:
As the name indicates their recovery time is very low, generally less than 5ms. Their
current ratings are from about 1 A to hundreds of amperes and voltage ratings from 50 V to about 3
kV.
3. The Schottky diode:
The Schottky diode is a low-voltage, high-speed device that works on a different principle
from that of the PN junction diode.
It is constructed without the usual PN junction. Instead, a thin barrier metal (such as
chromium, platinum, or tungsten) is interfaced with the N-type semiconductor.
This construction results in a low on-state voltage (about 0.6 V) across the diode when it
conducts. Furthermore, it can turn off much faster than a PN junction diode, so switching
frequency can be high. However, the reverse leakage current is much higher, and the reverse
breakdown voltage is lower compared with that of a PN junction diode.
Schottky diodes are therefore used as rectifiers in low-voltage applications where the
efficiency of conversion is important.
These diodes are also widely used in switching power supplies that operate at frequencies
of 20 kHz or higher.
Advantage of Power Diode
1. The PN-junction region of this diode is large & can supply huge current.
2. It will resolve AC at high current and a high voltage, it is used for rectification only.
Limitations
1. The main disadvantage is its size & probably needs to be fixed to a heat sink while
conducting a high current.
2. It needs specialized hardware for installing and insulating from the metal frames
which are available in the surrounding.
Application of Power diode
1. DC power supplies for charging the battery.
2. Inverters and AC rectifiers,

NOTES:

7
 3. Freewheeling- Snubber circuits and Blocking circuits.

NOTES:

8
 Power transistors
Power transistors are devices that have controlled turn-on and turn-off characteristics.
These devices are used a switching device and are operated in the saturation region resulting in low
on- state voltage drop. They are turned on when a current signal is given to base or control
terminal.
The transistor remains on so long as the control signal is present. The switching speed of modern
transistors is much higher than that of thyristor.
The voltage and current ratings are lower than those of thyristor and are therefore used in low to
medium power applications.
Power transistors are classified as follows.
1. Bipolar junction transistors (BJT)
2. Metal-oxide semiconductor filed-effect transistors (MOSFET)
3. Insulated-gate bipolar transistors (IGBT)
1. Bipolar junction transistors (BJT)
The BJT is a three-layer and two-
junction NPN or PNP semiconductor
device. Power n-p-n transistors are widely
used in high-voltage and high-current
applications. Input and output
characteristics of planar BJT for common-
emitter configuration.
BJT is a current-controlled device.

The device operates in quadrant I and is characterized by the plot of the collector current IC
versus the collector to emitter voltage VCE.
The device has three regions, two of them where the device operates as a switch.
During the ON-state: the device carries a collector current IC>0 with VCE = 0.
During the OFF state: the device supports positive VCE>0 with IC = 0.
Advantages of Power BJT
i. BJT have high switching frequencies since their turn-on and turn-off times are low.
ii. The turn-on losses of a BJT are small.
iii. BJT has controlled turn-on and turn-off characteristics since base drive control is possible.
iv. BJT does not require commutation circuits.

NOTES:

9
 Demerits of Power BJT
i. Drive circuit of BJT is complex.
ii. It has the problem of charge storage which sets a limit on switching frequencies.
iii. It cannot be used in parallel operation due to problems of negative temperature
coefficient.
Application of Power BJT
Switch-mode power supplies (SMPS)
DC to AC converters.
Power supply.
Power control circuits.
Inverters.
2. POWER MOSFETS.
MOSFET device belongs to the Unipolar Device family, it uses only the majority carriers in
conduction. The development of metal oxide semiconductor technology for microelectronic
circuits opened the way for developing the power metal oxide semiconductor field effect transistor
(MOSFET) device in 1975.
The device symbol for a p- and n-channel enhancement and depletion types the n-channel
enhancement-type MOSFET. It is the fastest power switching device with switching frequency
more than 1 MHz, with voltage power ratings up to 1000V and current rating as high as 300 A.

Power MOSFET is a Voltage controlling device.

MOSFET Structure

NOTES:

10
 POWER MOSFET is the combination of Parasitic Transistor and Integaral (Body Diode)

MOSFET is used as a switch in any application then the device will work within the regions
of ohmic & cut off once switched ON/OFF correspondingly.
Once the voltage of the gate-source is low as compared to the threshold voltage, then power
MOSFET will be in the cut-off region.

To maintain the MOSFET in the off-state, VGS must be less than a threshold voltage
known as VT, which is the region below the line marked OFF.
The device is ON it act as resistance determined by the slope of the line marked ON.

NOTES:

11
 Advantages of Power MOSFET
1. MOSFETs are the majority carrier devices.
2. MOSFETs have positive temperature coefficient, hence their paralleling is easy.
3. MOSFETs have very simple drive circuits.
4. MOSFETs have short turn on and turn off times; hence they operate at high frequencies.
5. MOSFETs do not require commutation circuits.
6. Gate has full control over the operation of MOSFET
Demerits of Power MOSFET
1. On-state losses in MOSFETs are high.
2. MOSFETs are used only for low power applications.
3. MOSFETs suffer from static charge. ‟
Application of Power MOSFET
1. High frequency and low power inverters.
2. High frequency SMPS.
3. High frequency inverters and choppers.
4. Low power AC and DC drives.
SL.
POWER BJT POWER MOSFET
NO
1 This is both majority and Minority
This is majority carrier device
carrier device
2 Controlled by base Controlled by Gate

3 Current controlled device Voltage controlled device

4 Negative temperature coefficient Positive temperature coefficient

5 Paralleling of BJT is difficult Paralleling MOSFETs is simple.

6 Losses are low Losses are higher

7 Drive circuit is complex Drive circuit is simple

8 Switching frequency is lower Switching frequency is high

BJTs are suitable for high power MOSFETS are suitable for low power
9
application application
BJTs are available with higher MOSFETs have less voltage and current
10
voltage and current ratings ratings
4. IGBT
The Insulated Gate Bipolar Transistor (IGBT) is the latest device in power electronics. It is
obtained by combining the properties of BJT and MOSFET.

NOTES:

12
 The IGBT is a hybrid or also known as double mechanism device. Its control port
resembles a MOSFET, and its output or power port resembles a BJT.
Combines the fast switching of a MOSFET and the low power conduction loss of a BJT.
IGBT, which is slightly different from MOSFET with similar terminal labels. The control
terminal is labeled as gate (G) and the power terminals are labeled as collector (C) and emitter (E).

Structure of IGBT

The structure of IGBT is like that of that of MOSFET. Fig. Shows the vertical cross section
of IGBT. In this structure observe that there is an additional P+ layer. This layer is a collector
(Drain) of IGBT.
This P+ injecting layer is heavily doped. It has an intensity of 10 19 per cm3. The doping of
other layers is like that of MOSFET. N+ layers have 10 19 per cm3. P-type body region has a doping
level of 1016 per cm3. Then the drift region is lightly doped (1014 per cm3).
Punch through IGBT

NOTES:

13
 The n+ buffer layer is not necessary for the operation of IGBT. The IGBT which has n+
buffer layer is called punch through IGBTs. Such IGBTs have asymmetric voltage blocking
capabilities. Punch through IGBTs have faster turn-off times.
Non-punch through IGBT
The IGBTs without n+ buffer layer is called non-punch IGBTs. These IGBTs have
symmetric voltage blocking capabilities.

The I-V characteristics of a real IGBT are shown in Figure (b), which shows that the device
operates in quadrants I and III.
The ideal characteristics of the device are shown in Figure (c). The device can block
bidirectional voltage and conduct unidirectional current.
An IGBT can change to the ON-state very fast but is slower than a MOSFET
device. Discharging the gate capacitance completes control of the IGBT to the OFF
state.
IGBTs are typically used for high power switching applications.
Advantages of IGBT
1. Voltage controlled device. Hence the drive circuit is very simple.
2. on state losses are reduced.
3. Switching frequencies are higher than Thyristors.
4. No commutation circuits are required.
5. Gate has full control over the operation of IGBT.
6. IGBTs have approximately flat temperature coefficient.
Demerits of IGBT
1. IGBTs have static charge problems.
2. IGBTs are costlier than BJTs and MOSFETs.
Application of IGBT
1. Appliance motor drives
2. Electric vehicle motor drives
3. Power factor correction converters
4. Uninterruptible power supplies
5. Solar inverters
6. High frequency welders
7. Inductive heating cookers

NOTES:

14
 5. Thyristors
Thyristors (also known as the Silicon Controlled Rectifiers or SCRs) have come a long way
from this modest beginning and now high-power light triggered Thyristors with blocking voltage
more than 6kv and continuous current rating more than 4kA are available.
Along the way many other devices with broad similarity with the basic thyristor (invented
originally as a phase control type device) have been developed.
They include,
Inverter grade fast thyristor
Silicon Controlled Switch (SCS)
Light activated SCR (LASCR)
Asymmetrical Thyristor (ASCR)
Reverse Conducting Thyristor (RCT)
Diac
Triac
Gate turn off thyristor (GTO)

Silicon Controlled Rectifiers (SCR)

A silicon-controlled rectifier or semiconductor-controlled rectifier is a four-layer solid state
current- controlling device. The name is "silicon-controlled rectifier, four layers of
semiconductors that form two structures namely, NPNP or PNPN. In addition, it has three
junctions labeled as J1, J2 J3 and three terminals.
It has three terminals:
the anode (A) is the positive power terminal.
2. the cathode (K) is the negative power terminals
3. The gate (G) is the control terminal.

NOTES:

15
 Basic operating principle of a thyristor
1. Forward blocking mode (off state)
2. Forward conduction mode (on state)
3. Reverse blocking mode (off state)
Forward blocking mode
In this mode of operation, the anode is given a positive voltage while the cathode is given a
negative voltage, keeping the gate at zero (0) potential. Junction J1and J3 are forward-bias,
while J2 is reverse-bias Allowing only a small leakage current from the anode to the cathode.
When the applied voltage reaches the break over value for J2, then J2 undergoes avalanche
breakdown. At this break over voltage J2 starts conducting, but below break over voltage J2 offers
very high resistance to the
current and the SCR is said to
be in the off state.
Forward conduction mode

In
this

conduction mode in two ways: Either by increasing the

voltage between anode and cathode beyond the break over voltage, or by applying a positive pulse
at the gate. Once the SCR starts conducting, no more gate voltage is required to maintain it in
the ON state. The minimum current necessary to maintain the SCR in the ON state on removal of
the gate voltage is called the latching current.
There are two ways to turn it off:
1. Reduce the current through it below a minimum
value called the holding current, or
2. With the gate turned off, short-circuit the anode and
cathode momentarily with a push-button switch or
transistor across the junction. Reverse blocking
mode

NOTES:

16
 In this mode negative voltage is applied to the anode and a positive voltage to the cathode,
the SCR is in reverse blocking mode, making J1 and J3 reverse biased and J2 forward biased.

The device behaves as two diodes connected in series. A small leakage current flow. This is
the reverse blocking mode. If the reverse voltage is increased, then at critical breakdown level,
called the reverse breakdown voltage (VBR).
An SCR incapable of blocking reverse voltage is known as an asymmetrical SCR,
abbreviated ASCR. It typically has a reverse breakdown rating in the tens of volts.
V-I characteristics of the SCR.
Forward Break over Voltage
Latching current
Holding current
Forward anode current rating
Peak reverse voltage
Circuit fusing rating
Forward Break over Voltage
The minimum forward voltage at which SCR starts conducting in the absence of the gate
current. This minimum voltage is the forward break-over voltage of SCR.
Latching Current
The latching current is the minimum anode current at SCR that remains in on state after
removing the gate current. If the value of anode current is less than the latching current value.
The SCR will not continue to be conducted.
Holding current
It is the maximum anode current at which the SCR turns off from its state. If the holding
current is 10 mA, the SCR will turn off if the anode current is less than 10 mA.
Forward anode current ratting
The maximum anode current can flow through the SCR, and it does not cause damage to
the SCR. The SCR is available in different anode current ratings. A 50 ampere forward current
rating SCR can carry the current safely.
Peak reverse voltage
The peak reverse voltage is the maximum reverse voltage across SCR (Cathode -positive
and anode – negative) that can be safely applied without conducting the SCR.

NOTES:

17
 Circuit Fusing Rating
The circuit fusing rating indicates the maximum forward surge current capability of SCR.
The circuit fusing rating depends on the current and time. The fusing rating of SCR is I2t. The
heating of SCR must be below the rated fusing rating for reliable SCR operation.

Advantages of SCR
1. It can manage large voltages, currents, and power.
2. The voltage drops across conducting SCR is small.
3. This will reduce the power dissipation in the SCR.
4. Easy to turn on.
5. Triggering circuits are simple.
6. It can be protected with the help of a fuse.
7. We can control the power delivered to the load.

Demerits of SCR
1. It can conduct only in one direction. So, it can control power only during one half cycle of
ac.
2. It can turn on accidentally due to high dv/dt of the source voltage.
3. It is not easy to turn off the conducting SCR. We must use special circuits called
commutation circuits to turn off a conducting SCR.
4. SCR cannot be used at high frequencies. The maximum frequency of its operation is 400 Hz.
5. Gate current cannot be negative.
Application of SCR
1. Controlled rectifiers.
2. DC to DC converters or choppers.
3. DC to AC converters or inverters.
4. As static switch.
5. Battery chargers.
6. Speed control of DC and AC motors.
7. Lamp dimmers, fan speed regulators.
8. AC voltage stabilizers.

NOTES:

18
 Gate turn-off thyristor (GTO)
A gate turn-off thyristor (known as a GTO) is a three
terminal power semiconductor device. GTOs belong to a
thyristor family having a four-layer structure. GTOs also
belong to a group of power semiconductor devices that have
the ability for full control of on- and off-states via the control
terminal (gate).
Conventional thyristor, applying a positive gate signal
to its gate terminal can turn-on to a GTO. Unlike a standard
thyristor, a GTO is designed to turn-off by applying a negative
gate signal.
Structure and Operation
The basic structure of a GTO consists
of a four-layer-PNPN semiconductor device, it
has several design features which allow it to be
turned on and off by reversing the polarity of
the gate signal. The most important differences
are
that the GTO has long narrow emitter fingers surrounded by gate electrodes and no cathode
shorts. The turn-on mode is like a standard thyristor.
The injection of the holes current from the gate forward biases the cathode p-base junction
causing electron emission from the cathode. These electrons flow to the anode and induce holes
injection by the anode emitter. The injection of holes and electrons into the base regions continues
until charge multiplication effects bring the GTO into conduction. The GTO thyristor is a device
that operates like a normal thyristor except the device physics, design and manufacturing features
allow it to be turned-off by a negative gate current which is accomplished with a bipolar transistor.

NOTES:

19
 Advantages of GTO
1. The GTO has a high capability of blocking voltage.
2. The GTO has more di/dt ratings at turn ON.
3. It has faster turn OFF permitting high switching frequencies.
4. The communication circuit is not required, hence it reduced size, weight, and cost.
5. It has high efficiency.
Demerits of GTO
1. In GTO, ON state voltage drops and the associated loss is more.
2. Gate drive circuit losses are more.
3. Triggering gate current is higher as compared to the current required for a conventional
SCR.
4. In GTO, magnitude of latching and holding current is more.

Application of GTO
1. In choppers as well as inverters, it is used as the main control device.
2. AC drives
3. DC drives
4. DC circuit breakers
5. DC choppers otherwise DC drives
6. Induction heating
7. Used in traction applications because of less weight
8. Low power applications
9. AC stabilize power supplies
10. It is used in inverters, SVCs (static VAR compensators)
11. Used in drive systems like rolling mills, machine tools & robotics.

NOTES:

20
 3.0 INVERTERS
3.1 Introduction
The converters which convert DC power into AC power are popularly known as inverters.

Classification of inverters
1. According to Commutation methods
Line commutated inverter
Forced commutated inverter.
2. According to Output phases
Single phase
Three phases
3. According to Supply sources
Voltage source inverter
Current source inverter
4. According to voltage
waveform Sinusoidal
inverter
Non – sinusoidal inverter
5. According to connection of semiconductor
devices Bridge inverter: Half bridge, Full
Bridge Series inverter
Parallel inverter

NOTES:

21
 3.2 Basic concepts of switch mode Inverters

Block diagram of a motor drive where the power flow can be bi-directional.

3.3 Single phase Inverters

Single phase Inverter Types:
Single phase Half Bridge
Inverter Single Phase Full Bridge
Inverter Push Pull Inverter
Single phase Half Bridge Inverter
Inverters: convert Direct current into
Alternating current. By using of Thyristor
such as SCR, TRIAC. For single phase half
bridge inverters, two Thyristors (SCRs) are
required like that of Diode rectifier.

NOTES:

22
 Working of Half bridge inverter

The Thyristor T1 is turned ‘ON’ by giving a gate pulse it. The Thyristor T2 is kept ‘OFF’,
and no gate signal is given to it.
Thus, the ThyristorT1 starts conducting and the current starts to flow from Edc/2(positive
terminal of 1st source)-T1-Load-negative terminal of 1st source.
Thus, a positive cycle like that of ac cycle is obtained.
The Thyristor T2 is turned ‘ON’ by giving a gate pulse it. The Thyristor T1 is kept ‘OFF’,
and no gate signal is given to it.
Thus, the ThyristorT2 starts conducting and the current starts to flow from Edc/2(Negative
terminal of 2nd source)-T2-Load-positive terminal of 2nd source.
Thus, a Negative cycle like that of ac cycle is obtained.
Drawback of Half bridge inverter
1. Two electrolytic capacitors connected in series are needed at the dc input side.
2. It is unable to generate zero output voltage intervals for non-resistive loads

NOTES:

23
 Single phase Half Bridge Inverter

S1 and S2 turned on in the first half cycle (T/2)

S3 and S4 turned on in the second half cycle (T/2)
A push–pull converter.

It is a type of DC-to-DC converter, a switching converter that uses a transformer to change

the voltage of a DC power supply.
The distinguishing feature of a push-pull converter is that the transformer primary is
supplied with current from the input line by pairs of transistors in a symmetrical push-pull circuit.
Application of Single-phase inverters
1. Adjustable-speed ac drives
2. Induction heating
3. Standby aircraft power supplies
4. UPS (uninterruptible power supplies) for computers
5. HVDC transmission lines.

NOTES:

24
 SL.NO HALF BRIDGE INVERTER FULL BRIDGE INVERTER
The efficiency is high in half-bridge In full-bridge inverter also, the efficiency
1 inverter is high
In half-bridge inverter the output In full-bridge inverter the output voltage
2 voltage waveforms are square, quasi waveforms are square, quasi square or
square or PWM PWM
The peak voltage in the half-bridge The peak voltage in the full-
3 inverter is half of the DC supply bridge inverter is the same
voltage as the DC supply voltage
The half-bridge inverter contains two The full-bridge inverter contains four
4 switches switches
5 The output voltage is E0= EDC /2 The output voltage is E0= EDC
The fundamental output voltage is E1= The fundamental output voltage is E1=
6 0.45 EDC 0.9 EDC
This type of inverter generates bipolar This type of inverter generates monopolar
7 voltages voltages

3.4 Three Phase Invertor:

A three-phase AC power can be generated by using three independent DC-AC converters.
Alternatively, a modification of a single-phase full-bridge configuration makes three-phase
inverters. These three-phase Inverters are of two types depending upon conduction period of each
switch:
(i) 180o conduction mode
(ii) 120o conduction mode.
(i) 180o conduction mode
In this control scheme, each switch conducts for a half-cycle for 180 o. The gate voltage
signals are generated and supplied in a particular sequence.
Three-phase, 4-wire, Y-connected load: The circuit configuration of the inverter with
balanced three-phase, 4-wire, Y-connected load.
In this case a neutral connection is also required which is connected to the inverter. Due to
four wire system, the load of each phase is independently connected to the switch. When the upper
switches (S1, S3, S5) are closed, the load (R) gets connected to +V bus. As N is connected to O,
the midpoint of input voltage, +V appears at load (R). Similarly, when the lower switches (S2, S4,
S6) are closed, the load (R) gets V voltage.
These signals are displaced by 60o, sequentially which also show the conduction period of
switches and the output voltage of each phase appears at load accordingly.

NOTES:

25
 It must be ensured that both switches of the same leg should not be turned on
simultaneously otherwise it would cause a short-circuit of the input DC source.

NOTES:

26
 120 Conduction:
In this conduction each switch conducts for 120o duration and two switches conduct
simultaneously in the sequence S6&S1, S1&S2, S2&S3, S3&S4, S4&S5, and S5&S6. The
switching schemes.
A gap or delay of 60 is appears between the turning on and turning off two switches of the
same leg. Thus, the short-circuit condition of the input DC source is avoided. As only two switches
conduct at a time, thus one load terminal remains idle.

NOTES:

27
 Application of Three phase Inverter.
1. In variable frequency drive applications
2. HVDC power transmission.
3. A three-phase square wave inverter is used in a UPS circuit
4. Low-cost solid-state frequency charger circuit.

4.0 POWER SUPPLIES

4.1 Introduction
Electric power is not normally
used in the form in which it is
produced or distributed. Practically all
electronic systems require some form
of Power conversion.
A device that transfers electric energy from a source to a load using electronic circuits is
referred to as a power supply.
A typical application of a power supply is to convert utility AC voltage into regulated DC
voltages required for electronic equipment.
There are two broad categories of power supplies:
1. Linear regulated power supply (RPS)
2. Switched mode power supply (SMPS)

NOTES:

28
 4.2 Linear regulated power supply (RPS)

A DC supply consists of the following parts:

1. The AC voltage is connected to a transformer, which steps that ac voltage down to the
level for the desired dc output.
2. A diode rectifier then provides a full-wave rectified voltage.
3. This is initially filtered by a simple capacitor filter to produce a dc voltage.
4. This resulting dc voltage usually has some ripple or ac voltage regulation.
5. A regulator circuit can use this dc input to provide a dc voltage that not only has much
less ripple voltage but also remains the same dc value even if the input dc voltage varies somewhat
or the load connected to the output dc voltage changes.
6. This voltage regulation is usually obtained using one of the voltage regulator IC units.
Concept of Voltage Regulation:

The function of a linear voltage regulator is to convert a varying DC voltage to a constant.

In addition, they often provide a current limiting function to protect the power supply and load
from overcurrent (excessive, potentially destructive current).

A constant output voltage is required in many power supply applications, but the voltage
provided by many energy sources will vary with changes in load impedance.

The unregulated DC power supply is the energy source, its output voltage will also vary
with changing input voltage. To circumvent this, some power supplies use a linear voltage
regulator to maintain the output voltage at a steady value, independent of fluctuations in input
voltage and load impedance. Linear regulators can also reduce the magnitude of ripple and noise on
the output voltage.

Line Regulation:

NOTES:

29
 It is the percentage change in the output voltage for a given change in the input voltage.
It can be expressed in units of (%/V).

Load Regulation:

It is the percentage change in output voltage for a given change in load current. One way to
express load regulation is as a percentage change in output voltage from no-load (NL) to full load
(FL).

A Zener-Regulated DC Power Supply:

Series Linear Voltage Regulator

The control element is a pass transistor in series
with the load between the input and output.
The output sample circuit senses a change in the
output voltage.
The error detector compares the sample voltage
with a reference voltage and causes the control element to
compensate to maintain a constant output voltage.

NOTES:

30
 Integrated Circuit Voltage Regulators
Integrated circuit voltage regulators are available as series regulators.
The IC regulator contains the reference voltage, the error detector, and the control unit in one
package.

Fixed Positive Linear Regulator 78XX

Fixed Negative Linear Regulator 79XX

NOTES:

31
 Variable Positive Linear Regulator (LM317)

Variable Negative Linear Regulator (LM337)

4.3 SWITCHED MODE POWER SUPPLIES (SMPS)

Basic concept of SMPS:
The dc output of the rectifier or battery is not regulated. It varies according to the load
variations. Switching mode regulators are used to convert unregulated dc to regulated DC output.
SMPS is based on the chopper principle. The output dc voltage is controlled by varying the
duty cycle of the chopper by PWM or FM technique. Generally, PWM technique is used. If power
transistors are used, the chopping frequency is limited to 40 KHz. For power MOSFETs, the
chopping frequency is up to 200 KHz.
Types of SMPS
SMPS are categorized into four different types.
1) AC-DC converter
2) DC-DC converter
3) Forward Converter
4) Fly back converter

NOTES:

32
 AC- DC Converter:
This type of SMPS has an AC input and it is converted into DC by using rectifier & filter.
The switching operation is done by using a power MOSFET amplifier and action of switching is
controlled by feedback using the PWM oscillator.
DC-DC converter:
In this power source, a high voltage DC power is directly acquired from a DC power source.
The switching-power supply o/p is regulated by using Pulse Width Modulation
Forward Converter:
This type of SMPS a control is connected at the output of the secondary winding of the
transformer to control the switch. As compared to the fly back converter, the filtering and
rectification circuit is complicated. This is also called a DC-DC buck converter.
Fly back converter
In this type of SMPS, output power is very low (less than 100W). This type of SMPS is
very simple circuit compared with other SMPS circuits. This type of SMPS is used for low power
applications.

BLOCK DIAGRAM OF SMPS

Working principle of SMPS

Input rectifier and filter:
This block rectifies the input AC voltage into pulsating DC and filters the DC to reduce the ripples.
High frequency switch:
MOSFET or Bipolar transistors are used as high frequency switch. It converts the DC
voltage into high frequency AC square wave of 20-100 KHZ.

NOTES:

33
 Power transformer:
The power transformer isolates the circuits and step up or step down the voltage to a level
required by DC the voltage.
Output rectifier and filter:
Here again AC voltage will be converted into DC voltage by rectifier. The filters are
used to make the output voltage ripple free and smooth. And the output ripple of high frequency
(20
– 100 KHz) ripple will be filtered by filter.
Output sensor:
It detects the output DC voltage and feedback it to the control circuit. Control circuit. In the
control circuit, the error amplifier compares the reference voltage with output voltage. The
reference voltage is set for the output voltage.
The error amplifier generates the error signal depending on the difference between output
voltage and reference voltage. The error signal acts as the control voltage to drive the high
frequency switch (chopper). This control voltage varies the width (duty cycle) of the pulse width
modulation (PWM) oscillator to adjust the switching speed of high frequency switch.
To reduce the DC voltage, pulse width will be reduced by control voltage.
To increase the DC voltage, pulse width will be increased by control voltage. By this
technique, a regulated dc output voltage can be obtained.
Advantages of SMPS
1. In linear power supply the series pass transistor operates in active region. Hence there is high
power loss. But in SMPS, devices operate in saturation and cut-off regions. Therefore, losses are
reduced in SMPS.
2. Due to reduced power loss, SMPS have efficiencies up to 95% but linear power supplies have
very small efficiencies.
3. SMPS operate at very high frequencies. Therefore, filtering components and transformers have
very small size. Linear power supplies have bulky components.
4. SMPS have transistors in switching mode. Hence their power handing capacity is more as
compared to linear mode.
5. SMPS are more cost effective due to reduced size of transformer and filters.

NOTES:

34
 Disadvantages of SMPS
1. SMPS operates at high switching frequencies, they generate Radio Frequency Interference (RFI)
to neighboring circuits.
2. Since the devices operate in switched mode, there are switching losses at high frequencies. 3.
The transient response of SMPS is very slow compared to linear power supplies
4. SMPS have poor load regulation as compared to linear power supply.
Application of SMPS
1. Televisions, DVD player.
2. Computer, printer, monitors.
3. Battery charges, electronic ballasts.
4. Video games, toys.
4.4 Protection
Reliable operation of a thyristor demands that its specified ratings are not exceeded.
There are two types of protection required.
Thyristor Protection
Over Voltage Protection
Over voltage occurring during the switching operation causes the failure of SCR.
Internal Overvoltage
It is due to the operating condition of SCR. During the commutation of SCR, when the
anode current decays to zero anode current reverses due to stored changes. First the reverse current
rises to peak value, then reverse current reduces abruptly with large di/dt.
External over Voltage
This is due to external supply and load condition. This is because of
1. The interruption of current flow in an inductive circuit.
2. Lightening strokes on the lines feeding the thyristor systems.
Suppose a SCR converter is fed from a transformer, voltage transient occurs when transformer
primary will energize or de-energized.
This overvoltage causes random turn ON of a SCR. The effect of overvoltage is minimized
using.
The surge condition over voltage clamping device returns to high resistance state.

NOTES:

35
 Voltage clamping device.
1. Selenium thyristor diodes
2. Metal Oxide Varistors
3. Avalanche diode suppressors.
1. DI/DT Protection

If the rate of rise of anode current, i.e., di/dt is large as compared to the spread velocity of
carriers, local hot spots will be formed near the gate connection. This localized heating may
destroy the thyristor. The value of di/dt can be maintained below acceptable limit by using a small
inductor, called di/dt inductor in series with the anode circuit. Typical di/dt limit value of SCRs are
20-500 A/μ-sec.

2. DV/DT Protection

If the rate of rise of suddenly applied voltage across thyristor is high, the device may get
turned on. It leads to false operation of the thyristor circuits. Typical values of dv/dt are 20-500
V/μ- sec. False turn-on of a thyristor by large dv/dt can be prevented by using a snubber circuit in
parallel with the device.

Isolation

The isolator between gate driver and power MOSFET. There are many topologies about the
peripheral circuit.

Types of Isolators used in protection circuit.

1. Pulse transformation

2. Opto Isolator

1. Pulse transformation

A pulse transformer usually has galvanic isolation between its windings. This allows for the
primary driving circuit to operate at a different electric potential from the secondary driven circuit.
4 kV for small electronic transformers. The isolation can be very high. This is especially true for
very high-power applications in which the output voltage can reach 200 kV. The galvanic isolation

NOTES:

36
 also allows meeting safety requirements if one part of the circuit is unsafe to touch, due to the
danger of higher voltage, even if for a brief period (if current path is broken in series with
inductance)

Windings and turns ratio.

In most low-power or applications the turn’s

ratio is around unity 1:1 or similar like 1:2. The
level of signal must be changed to a different
voltage then a significantly different turn’s ratio
will be used. Pulse transformer can have more than
two windings, which can be used for instance to
drive several
transistors simultaneously. So that any phase shifts or delays between signals are minimized
between signals are minimized

2. OPTO Isolator

An Opto coupler, also known as an Opto-isolator or Photo-coupler. It is

an electronic component that interconnects two separate electrical circuits by
means of a light sensitive optical interface. We know from our tutorials about
Transforms that they can not only provide a step-down voltage, but they also provide ―electrical
isolation‖ between the higher voltage on the primary side and the lower voltage on the secondary
side. In other words, transformers isolate the primary
input voltage from the secondary output voltage using

electromagnetic coupling by means of a

magnetic flux circulating within the iron laminated
core. It is also providing electrical isolation between
an input source and an output load using just light by
using a very common and valuable electronic
component called an Opto coupler. The basic design

NOTES:

37
 of an opto coupler consists of an LED that

NOTES:

38
 produces infra-red light and a semiconductor photo-sensitive device that is used to detect
the emitted infra-red beam. Both the LED and photo-sensitive device are enclosed in a light-tight
body or package with metal legs for the electrical connections. An Opto coupler or Opto-isolator
consists of a light emitter, the LED and a light sensitive receiver which can be a single photodiode,
phototransistor, photo-resistor, photo-SCR, or a photo-TRIAC with the basic operation of an Opto
coupler being very simple to understand.

This type of opto coupler configuration forms the basis of a very simple solid state relay
application. It can be used to control any AC mains powered load such as lamps and motors. Also,
unlike a thyristor (SCR), a Triac can conduct in both halves of the mains AC cycle with zero-
crossing detection allowing the load to receive full power without the heavy inrush currents when
switching inductive loads.
Opto couplers and Opto-isolators are great electronic devices that allow devices such as
power transistors and Triac to be controlled from a PC ‘s output port, digital switch or from a low
voltage data signal such as that from a logic gate. The main advantage of opto-couplers is their
high electrical isolation between the input and output terminals allowing relatively small digital
signals to control much large AC voltages, currents, and power.
Opto coupler Applications
1. Microprocessor input/output switching,
2. DC and AC power control,
3. PC communications,
4. Signal isolation and power supply regulation which suffer from current ground loops,
5. The electrical signal being transmitted can be either analogue (linear) or digital (pulses)

NOTES:

39
 5.0 UPS
An uninterruptible power supply, also uninterruptible power source, UPS, or
battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when
the input power source or mains power fails.
A UPS differs from an auxiliary or emergency power system or standby generator in that it
will provide near-instantaneous protection from input power interruptions, by supplying energy
stored in batteries, super capacitors, or flywheels.
The on-battery runtime of most uninterruptible power sources is relatively short (only a few
minutes) but sufficient to start a standby power source or properly shut down the protected
equipment.
UPS is typically used:
1. To protect hardware such as computers Data centers
2. Telecommunication equipment or other electrical equipment where an unexpected power
disruption could cause injuries, fatalities
3. Business disruption or data loss.
4. UPS units’ range in size from units designed to protect a single computer without a video
monitor (around 200-volt-ampere rating)
5. Large units powering entire data centers or
buildings. Types of UPS
1. Offline UPS
2. Online UPS
5.1. Offline UPS

NOTES:

40
 The offline/standby UPS (SPS) offers only the most basic features, providing surge
protection and battery backup.
In this system, the main AC supply is rectified to DC. This DC output from the rectifier
charges the batteries and is also converted to AC by an inverter. Under normal circumstances,
normally-on contacts are closed, and normally-off contacts are open. The main supply delivers ac
power to the load through Normally On contacts. At the same time, the rectifier supplies
continuous charge to batteries to keep them fully charged.
In the event of power failure, normally-off switch is turned –on and the batteries deliver ac
power to critical load through the inverter and filter. A momentary interruption may occur (4 to 5
ms) to the load. It is also called stand-by power supply.

5.1 Online/double-conversion

In this system, the main AC supply is rectified, and the rectifier delivers power to charge the batteries.
The rectifier also supplies power to inverter continuously which is then given to AC type of
load through filter and normally-on switch.
In case of main supply failure, batteries supply power to critical load without any interruption.
No discontinuity in the illumination is observed in the case of on-line UPS.
 In case inverter failure is detected, main ac supply directly applied to the load by turning on the
Normally-off static switch and opening the Normally-on static switch.
 The transfer of load from inverter to main AC supply takes 4 to 5 ms by static transfer switch as
compared to 40 to 50 ms for a mechanical contactor.
 After the inverter fault is cleared, uninterruptible power supply is again restored to the load
through the normally on switch.

NOTES:

41
 Advantages of Online UPS
i) Load is protected from transients in the main supply.
ii) Inverter output frequency can be maintained at the desired level.
iii) Inverter can be used to condition the supply delivered to load
COMPARISON OF OFF-LINE UPS AND ON-LINE UPS

6.0 ELECTROMECHANICAL DEVICES

6.1 RELAYS
Relays are the primary protection as well as switching devices in most of the control
processes or equipment’s. The relay is an important part of many control systems because it is
useful for controlling high voltage and current devices with a low voltage and current control
signal. Relays have NO (Normally open) or NC (Normally close) or combinations of both contacts.
Different Types of Relays:
1. Electromagnetic Relay
2. Magnetic Latching Relay
3. Solid State Relay (SSR)
4. Hybrid Relay
5. Thermal Relay
6. Reed Relay

NOTES:

42
 1. Electromagnetic Relay
These relays are constructed with
electrical, mechanical, and magnetic
components, and have operating coil and
mechanical contacts. Therefore, when the
coil gets activated by a supply system, these
mechanical contacts get opened or closed.
The type of supply can be classified 1. AC Relay or DC.
Magnetic Latching Relay
These relays use permanent magnet or parts with a high remittance to remain the armature
at the same point when the coil power source is taken away.
Solid State Relay (SSR)
Solid State uses solid state components such as Transistors, SCR, TRIAC, and DIAC to
perform the switching operation without moving any parts. Since the control energy required is
much lower compared with the electromagnetic relay that results the high-power gain. These are of
different types: reed relay coupled SSR, transformer coupled SSR.

Hybrid Relay
These relays are composed of electromagnetic relays and electronic components. Usually,
the input part contains the electronic circuitry that performs rectification and the other control
functions, and the output part includes electromagnetic relay.
Thermal Relay
These relays are based on the effects of heat, which means that the rise in the ambient
temperature from the limit, changes the contacts in switch from one position to another. These are
mainly used in motor protection and consist of bimetallic elements; it is temperature sensors as
well as control elements. Thermal overload relays

NOTES:

43
 Reed Relay
Reed Relays consist of a pair
of magnetic strips (also called reed)
that is sealed within a glass tube.
This reed acts as both an armature
and a contact blade. When the
magnetic
field is applied to the coil which is wrapped around this tube, reeds move towards each one and get
close contact. So that switching operation is performed.
Based on dimensions, relays are differentiated as micro miniature, subminiature, and
miniature relays. Also, based on the construction, these relays are classified as hermetic, sealed,
and open type relays. Furthermore, depending on the load operating range, relays are of micro,
low, intermediate, and high-power types.

Application of Relays:
1. Control panels,
2. Manufacturing
3. Building automation
4. Control the power along with switching the smaller current values in a control
circuit.
6.1 Solenoid
It is an electromechanical valve that operates using an in-built actuator in the form of an
electrical coil and a plunger.
An electrical signal controls the opening and closing of the solenoid valve. There are two
modes in which solenoid valves are produced. They are normally open and normally closed. The
solenoid (electrical coil) is operated using an AC or DC

NOTES:

44
 DC supplies are provided through a battery, generator, or rectifier. Whereas an AC supply
is usually taken from AC mains voltage, through a
transformer.
A solenoid valve has two main
components: a solenoid and a valve body (G).
The electromagnetically inductive coil (A)
around an iron core at the center is known as the
plunger (E). At rest, it will be either normally
open (NO) or normally closed (NC). During the
de-energized phase, a normally open valve
remains open while a normally closed valve
remains closed. When current flows through the
solenoid coil, it is
energized and creates a magnetic field that creates a magnetic attraction with the plunger. This, the
plunger moves by overcoming the spring (D) force. For a normally closed solenoid valve, the
plunger is lifted, and the seal (F) opens the orifice allowing the media to flow through the valve.
While for a normally open solenoid valve, the plunger moves downward, and the seal (F) blocks
the orifice which stops the media from flowing through the valve. The shading ring as denoted by
(C) prevents vibration and humming in AC coils.
Types of Solenoids
1. Two-Way Solenoid Valves
2. Three-Way solenoid Valves
3. Four-Way Solenoid Valves
4. General-purpose solenoid valves
5. Safety shut-off valves and
6. Process-control valves
7. Direct-acting solenoid valves
8. Pilot-operated solenoid valves
9. Pressure-operated solenoid valves
10. Air-operated solenoid valves

NOTES:

45
 Application of Relay
1. Solenoid valves in refrigeration systems reverse the refrigerant flow that cools during
summer and heats during winter.
2. Solenoid valves are used in compressors during the starting phase to discharge the
compressor to reduce the torque on the engine.
3. Solenoid valves are used in irrigation systems for automatic control purposes.
4. Solenoid valves in washing machines and dishwashers control the water flow as per
requirement.
5. Air pressure in air conditioning systems is controlled by solenoid valves.
6. Automatic locking systems for door locks use solenoid valves.

7. Car washes and Industrial cleaning equipment use solenoid valves to control the water,
soap, or chemical flow.
8. The inflow and outflow of water in water tanks are often controlled using solenoid valves.
9. The pressure, flow, and fluid direction in controlled by solenoid valves in dental and
various medical equipment.
6.1 Miniature Circuit Breaker (MCB)
A miniature circuit breaker (MCB) is an Electrical Switch that automatically switches off
the electrical circuit during an abnormal condition of the network means an overload
condition as well as a faulty condition. MCB in a low-voltage electrical
network instead of a fuse. The fuse may not sense it, but the miniature circuit
breaker does it in a more reliable way. MCB is much more sensitive to
overcurrent than a fuse. MCB working:
An MCB works by detecting the current flowing through an electrical circuit. If
the current exceeds the maximum level set for the MCB, it will automatically trip and interrupt the circuit.
Types of Miniature Circuit Breaker
Miniature circuit breakers are classified on their ability to work on the number of poles.
1. Single Pole: As the name suggests, the single-pole MCB is used for circuits working on a single
phase.
2. Double Pole: A double-pole MCB provides protection for the phase and neutral of the circuit.
3. Triple Pole: A triple-pole MCB provides switching protection for three phases of the circuit
which are RYB (standard Colour coding of wire)

NOTES:

46
 4. Triple Pole with Neutral: This kind of MCB provides protection to three phases of the circuit
just like a three-pole MCB but along with that the neutral is also a part as a separate pole in the
MCB.
5. Four Pole: The four pole is similar in construction to a three-pole MCB, but it has a protective
release for the neutral pole.
Miniature circuit breakers are also classified according to their tripping characteristics which are:
1. Type B – Tripping current is 3 to 5 times the full load current.
2. Type C – Tripping current is 5 to 10 times the full load current.
3. Type D – Tripping current is 10 to 20 times the full load current.
4. Type K – Tripping current is 8 to 12 times the full load current.
5. Type Z – Tripping current is 2 to 3 times the full load current.
Application of MCB
The right MCB for a specific application depends on factors such as the current rating of the
circuit,
The type of load being powered, and the type of protection required. It is important to consult
with a qualified electrician or engineer to determine the appropriate MCB for a specific application.
6.1 Switches:
A Switch is a device which is
designed to interrupt the current flow
in a circuit. In simple words, a
Switch can make or break an
electrical circuit. Every electrical and
electronics application uses at least
one switch to perform ON and OFF
operation of the device.
A switch can perform two functions, namely fully ON (by closing its contacts) or fully OFF
(by opening its contacts).
Switches can be of three types.
1. Mechanical
2. Electromechanical
3. Electronic

NOTES:

47
 Mechanical Switches
Mechanical switches can be classified into different types based on several factors such as
method of actuation (manual, limit, and process switches).
Number of contacts (single contact and multi contact switches), number of poles and
throws (SPST, DPDT, SPDT, etc.)
Operation and construction (push button, toggle, rotary, joystick, etc.)
Based on state (momentary and locked switches)

Electromechanical Switches
Electromechanical switches use mechanical actions to change the direction or orientation of
path continuity within its terminal.
There are many uses for switches for electronics items: power supply main switches,
various switches used to control aspects of performance, often on more professional items of
electronic equipment, switches for electronic equipment used for many professional equipment,
and very many other uses. They are commonly found on many household items, and automotive
applications because of their durable construction and simple operation.

NOTES:

48
 1. Relay
2. Contactor
3. Solenoid

Electronic Switches
The electronic switches are called as Solid-State switches because there are no physical
moving parts and hence no physical contacts. Most of the appliances are controlled by
semiconductor switches.
There are several types of solid-state switches are, varied sizes and ratings.
These solid-state switches include transistors, SCR, MOSFET, Triac and IGBT.
7.0 Handling of Electronics components.
7.1 ESD
Electrostatic discharge is defined as the transfer of electrostatic charges between bodies at
different potential caused by direct contact or induced electrostatic field.
Electrostatic Discharges (ESD) are the most severe form of Electromagnet Interference
(EMI).
The human body can build up static charges that range up to 25,000 volts. These build-ups
can discharge very rapidly into an electrically grounded body, or device. Placing a 25,000-volt surge
through any electronic device is potentially damaging to it.
The most common causes of ESD
1. Moving people
2. Improper grounding
3. Unshielded cables
4. Poor connections
5. Moving machines
6. Low humidity (hot and dry conditions)
Static generation:
Friction
Separation
Induction

NOTES:

49
 Electrostatic discharge process
1. Charge is generated on the surface of an insulator.
2. This charge is transferred to a conductor by contact or induction.
3. The charged conductor comes near a metal object (grounded or ungrounded) a discharge
occurs.
4. When a discharge occurs to an ungrounded object, the discharge current flows through the
capacitance between the object and ground.

ESD SOURCES:
Man Made Sources
Plastics
Conductors
Furniture's
Vinyl floor
Cooling fans with plastic blades
Printers/Copiers
Paper
Nylon & Woolen garments
Compressed air gun
ESD SOURCES NATURAL:
Human body
Movement of clouds
What Happens When ESD damage occurs?
1. Electronic Components damages by sudden transfer of Charges.
2. The Damages occurred cannot be identified visually.
3. All testing passes in manufacturing assembly.
4. Reach the Customer/Field
5. Work for a While with Customer & problems starts arising.

NOTES:

50
 Most Common Practice which leads to ESD failures

Impacts of ESD damages

Customer failures
Unsatisfied customers
Loss of orders
Poor company Reputation
ESD PROTECTING DEVICES:

ESD ANTISTATIC FABRICS ESD STORAGE BOX ESD HAND GLOVES

SHOES

ESD CAUTION TAPES

ESD RELATED TAPES ESD BRUSHES FOR CLEANING

ESD CAUTION TAPES ESD TWEEZERS

NOTES:

51
 PERSONAL GROUNDING

NOTES:

52
 MSD-MOISTURE SENSITIVES DEVICE
Moisture sensitive devices or MSD are components that are packaged within plastic that are
sensitive to damage related to atmospheric humidity.
During solder reflow, the combination of rapid moisture expansion and materials mismatch
can result in package cracking and/or delamination of critical interfaces within the package.
These internal defects are nearly impossible to detect during the PCB assembly and test
process. They lead to several failure modes that have a negative impact on manufacturing yields
and cause early life failure of the finished electronic products.

NOTES:

53