Electrical Basics Equipment's .

1. Electrical basics
Prepared by
Mr. Vijay Balu Raskar

2. Mr. Vijay Balu Raskar
B.E.Electrical
AutoCad-2D+3D
Mumbai University

3. Contents
• Fuse
• A circuit breaker
• A relay
• A contactor
• Suppression Diodes:
• Wiring
• American wire gauge (AWG)
• Current transformer
• Phase monitoring relay
• Ground fault interrupter (GFI)
• Emergency off (EMO) Switch
• Cable Basics
• Heat Shrink tubing
• Busbar
• Restriction of Hazardous Substances Directive (ROHS)
• Contact
• Thanks giving

4. • Fuse - is a type of over current protection device. Its essential component is a metal
wire or strip that melts when too much current flows, which interrupts the circuit in
which it is connected. Short circuit, overload or device failure is often the reason for
excessive current. A fuse interrupts excessive current (blows) so that further
damage by overheating or fire is prevented.

5. • A circuit breaker is an automatically operated electrical switch designed to protect
an electrical circuit from damage caused by overload or short circuit. Its basic
function is to detect a fault condition and, by interrupting continuity, to
immediately discontinue electrical flow. Unlike a fuse, which operates once and
then has to be replaced, a circuit breaker can be reset (either manually or
automatically) to resume normal operation.
• In - rated current of a circuit breaker for low voltage distribution applications as the
current that the breaker is designed to carry continuously (at an ambient air
temperature of 30 °C).
• Instantaneous tripping current, that is the minimum value of current that causes
the circuit-breaker to trip without intentional time delay (i.e., in less than 100
ms), expressed in terms of In

6. Type B devices are generally suitable for domestic applications. They may also
be used in light commercial applications where switching surges are low or
non-existent.
Type C devices are the normal choice for commercial and industrial
applications where fluorescent lighting, motors etc. are in use.
Type D devices have more limited applications, normally in industrial use
where high inrush currents may be expected. Examples include large battery
charging systems, winding motors, transformers, X-ray machines and some
types of discharge lighting.
Type B devices are designed to trip at fault currents of 3-5 times rated current
(In). For example a 10A device will trip at 30-50A.
Type C devices are designed to trip at 5-10 times In (50-100A for a 10A device).
Type D devices are designed to trip at 10-20 times In (100-200A for a 10A
device).

7. • A relay is an electrically operated switch. Relays are used where it is necessary to
control a circuit by a low-power signal (with complete electrical isolation between
control and controlled circuits), or where several circuits must be controlled by one
signal.
• A relay is used to isolate one electrical circuit from another. It allows a low current
control circuit to make or break an electrically isolated high current circuit path.
• A relay will switch one or more poles, each of whose contacts can be thrown by
energizing the coil in one of two ways:
• Normally-open (NO) contacts connect the circuit when the relay is activated; the
circuit is disconnected when the relay is inactive.
• Normally-closed (NC) contacts disconnect the circuit when the relay is activated;
the circuit is connected when the relay is inactive

9. • A contactor is an electrically controlled switch used for switching a power
circuit, similar to a relay except with higher current ratings. A contactor is
controlled by a circuit which has a much lower power level than the switched
circuit. Unlike a circuit breaker, a contactor is not intended to interrupt a short
circuit current.
• A type of relay that can handle the high power required to directly control an
electric motor is called a contactor.
• Contactors typically have multiple contacts, and those contacts are usually (but not
always) normally-open, so that power to the load is shut off when the coil is de-
energized. Perhaps the most common industrial use for contactors is the control of
electric motors.

10. • The top three contacts switch the respective phases of the incoming 3-phase AC
power, typically at least 480 Volts for motors 1 horsepower or greater. The lowest
contact is an "auxiliary" contact which has a current rating much lower than that
of the large motor power contacts, but is actuated by the same armature as the
power contacts. The auxiliary contact is often used in a relay logic circuit, or for
some other part of the motor control scheme, typically switching 120 Volt AC
power instead of the motor voltage. One contactor may have several auxiliary
contacts, either normally-open or normally-closed, if required.
• Unlike general-purpose relays, contactors are designed to be directly connected
to high-current load devices. Relays tend to be of lower capacity and are usually
designed for both normally closed and normally open applications. Devices
switching more than 15 amperes or in circuits rated more than a few kilowatts are
usually called contactors. Apart from optional auxiliary low current contacts,
contactors are almost exclusively fitted with normally open contacts. Unlike relays,
contactors are designed with features to control and suppress the arc produced
when interrupting heavy motor currents
• Applications - Contactors are used to control electric motors, lighting, heating,
capacitor banks, and other electrical loads.

11. Suppression Diodes: Anytime that a relay coil is driven by a circuit that is not
specifically designed to drive a relay, you should use a quenching/suppression diode
connected in parallel with the relay coil. The diagram below will show the
connection of the diode. Initially, you may think the diode serves no purpose because
the voltage applied to the relay cannot pass through the diode. This is true when the
relay is energized. The diode comes into play when the power source is removed
from the relay coil. When power is applied to the relay coil, a magnetic field is
created and energy is stored in the coil. When power is removed, the magnetic field
collapses causing a reverse voltage to be generated (it's called inductive kickback or
back EMF). The back EMF can easily reach 200 volts. The diode will absorb the
reverse voltage spike. This voltage, if not absorbed by the diode, will cause
premature failure of switch contacts and may cause the failure of power switching
transistors. You can use virtually any type of rectifier or switching diode (i.e.
1N4001, 1N4002, 1N400x... )

12. •Wiring - Three-phase electric power is a common method of alternating current electric
power generation, transmission, and distribution.
3Ph, 4 wire - Three-phase systems may have a neutral wire. A neutral wire allows the three-
phase system to use a higher voltage while still supporting lower-voltage single-phase
appliances.
3-Phase 5-Wire 208 V- This is the simply 3-phase power (3 hot wires and a ground) with a
neutral wire to provide 120 V.
Terminology:
Hot is any conductor (wire or otherwise) connected with an electrical system that has
electric potential relative to electrical ground or neutral.
A neutral wire is the return leg of a circuit; in building wiring systems the neutral wire is
connected to earth ground at least at one point
Ground is a conductor with continuity to earth

13. •American wire gauge (AWG) is a standardized wire gauge system used predominantly
in the United States and Canada for the diameters of
round, solid, nonferrous, electrically conducting wire. The cross-sectional area of each
gauge is an important factor for determining its current-carrying capacity.

14. •Current transformer In electrical engineering, a current transformer (CT) is used for
measurement of electric currents. Current transformers, together with voltage
transformers (VT) (potential transformers (PT)), are known as instrument transformers.
When current in a circuit is too high to directly apply to measuring instruments, a
current transformer produces a reduced current accurately proportional to the current
in the circuit, which can be conveniently connected to measuring and recording
instruments.
• A current transformer also isolates the measuring instruments from what may be
very high voltage in the monitored circuit. Current transformers are commonly
used in metering and protective relays in the electrical power industry.
• The primary circuit is largely unaffected by the insertion of the CT. The rated
secondary current is commonly standardized at 1 or 5 amperes. For example, a
4000:5 CT would provide an output current of 5 amperes when the primary was
passing 4000 amperes.

15. • Phase monitoring relay is designed to monitor the correct phase rotation or
sequence of 3 phase system L1, L2, L3. Rotation machines are particularly
vulnerable to incorrect phase sequence. Three Phase motors rotate in the wrong
direction, potentially leading to physical damage or the risk of injury to
personal, yet voltage & current reading may appear normal. If one phase is lost
because of a blown fuse, electric motors can continue to operate (single phase)
which can result in severe electrical or mechanical damage.
• This relay should be used to monitor the incoming supply, protecting all equipment
against incorrect connection at initial installation or after maintenance work.
Rotating machines that cannot tolerate reverse rotation or pose significant risk to
personal under this condition should be individually protected with this relay. The
possibility of incorrect supply connection is much more likely in portable equipment
or marine applications.

17. • Ground fault interrupter (GFI) - is an electrical wiring device that disconnects a
circuit whenever it detects that the electric current is not balanced between
the energized conductor and the return neutral conductor. Such an imbalance
is sometimes caused by current leakage through the body of a person who is
grounded and accidentally touching the energized part of the circuit. A lethal
shock can result from these conditions. GFIs are designed to disconnect quickly
enough to mitigate the harm caused by such shocks although they are not
intended to provide protection against overload or short-circuit conditions.
• GFIs are designed to prevent electrocution by detecting the leakage current,
which can be far smaller (typically 5–30 milli amperes) than the currents
needed to operate conventional circuit breakers or fuses (several amperes).
GFIs are intended to operate within 25-40 milliseconds, before electric shock
can drive the heart into ventricular fibrillation, the most common cause of
death through electric shock.
• GFIs are also commonly known as Ground fault circuit interruptor (GFCI),
Residual current device (RCD), Earth leakage circuit breaker (ELCB).

18. • Emergency off (EMO) Switch -is a switch when deactivated, places the equipment
into a safe shutdown condition and will restrict all hazardous potentials to the main
power enclosure. This is a condition in which all hazardous voltage has been
removed from the equipment, all hazardous production materials flow has been
stopped, any radiation sources have been de-energized or totally contained, any
capacitors have been grounded, all moving parts stopped, internal and external
heat sources shut off, and the equipment presents minimum hazard to personnel or
the facility.

20. • Cable Basics
• Conductor is a material which contains movable electric charges.
• Of the metals commonly used for conductors, copper has a high conductivity. Silver
is more conductive, but due to cost it is not practical in most cases. Aluminium has
been used as a conductor in housing applications for cost reasons.
• Electrical Wires are either solid or stranded Conductors. "Solid Conductors" are
exactly that, one solid Wire. "Stranded Conductors" consist of a Wire made of a
number of smaller Wire strands wrapped around each other. The choice between
solid or stranded depends on the need for flexibility in handling and working with
the Wire. Smaller electrical Wire Sizes are generally made of solid Conductors;
while Wires larger than Number 6 AWG are generally stranded.

21. • Insulation separates conductors electrically and physically within a cable.
• The jacket physically protects the internal components of a cable, improves the
cable’s appearance and provides flame retardancy.
• –Protects from the environment
• –Protects from the rigors of installation
• Drain Wire Metallic conductor frequently used in contact with foil-type signal-cable
shielding to provide a low-resistance ground return at any point along the shield.
• Twisted pair cabling is a type of wiring in which two conductors (the forward and
return conductors of a single circuit) are twisted together for the purposes of
canceling out electromagnetic interference (EMI) from external sources; for
instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and
crosstalk between neighboring pairs.

22. • Shielding - Contains electrical energy so that the signal on the cable does not
radiate and interfere with signals in other nearby cables and circuitry.
•Protects the signal from external interference.
Shielding materials-
• Metallic foil
• Braid
• French braid™
• Spiral (serve)
• Semi-conductive

23. • Heat Shrink tubing- is a sleeve ordinarily made of nylon or polyolefin, which
shrinks in diameter when heated. Its diameter and thickness can vary. Heat shrink
tubing is rated by its expansion ratio, a comparative of the differences in expansion
and recovery rate. Heat shrink is used to insulate wires offering abrasion resistance
and environmental protection for stranded and solid wire
conductors, connections, joints and terminals in electrical engineering. It can also
be used to repair the insulation on wires or to bundle them together, to protect
wires or small parts from minor abrasion, and to create cable entry seals, offering
environmental sealing protection between bulkheads and adding sealability to
electrical junction boxes.
• Common shrink ratio is 2:1, while high-grade polyolefin heat shrink is available in
3:1

24. • The tubing is placed over the connection to be protected and then heated with an
oven, hot air gun or similar tool. Convenient, but less effective, methods for
shrinking the tube include a soldering iron (held in close proximity, but not touching
the tube) or the heat from a lighter. These processes cause the tubing to contract
as far as one sixth of its original diameter (dependent on the heat shrink, 2:1 is the
most common), providing a snug fit over irregularly shaped joints. This provides
good electrical insulation, protection from dust, solvents and other foreign
materials, as well as strain relief. If overheated, heat shrink tubing can melt, scorch
or catch fire like any other plastic.
• Heat-shrink tubing is manufactured from a thermoplastic material such as
polyolefin, fluoropolymer (such as FEP, PTFE or Kynar), PVC, neoprene, silicone
elastomer or Viton.
• Heat shrink tubing is available in a variety of colors to allow easier color coding of
wires and connections.

25. • Busbar - In electrical power distribution, a busbar is a thick strip of copper or
aluminium that conducts electricity within a switchboard, distribution
board, substation or other electrical apparatus. Busbars are used to carry very
large currents, or to distribute current to multiple devices within switchgear or
equipment. Busbars are typically either flat strips or hollow tubes as these shapes
allow heat to dissipate more efficiently due to their high surface area to cross-
sectional area ratio.
• A busbar may either be supported on insulators, or else insulation may completely
surround it. Busbars are protected from accidental contact either by a metal
earthed enclosure or by elevation out of normal reach. Neutral busbars may also
be insulated. Earth busbars are typically bolted directly onto any metal chassis of
their enclosure.

26. • Restriction of Hazardous Substances Directive (ROHS) -The Directive on the
restriction of the use of certain hazardous substances in electrical and electronic
equipment 2002/95/EC (listen; commonly referred to as the Restriction of
Hazardous Substances Directive or RoHS) was adopted in February 2003 by the
European Union. The RoHS directive took effect on 1 July 2006, and is required to
be enforced and become law in each member state. This directive restricts the use
of six hazardous materials in the manufacture of various types of electronic and
electrical equipment. It is closely linked with the Waste Electrical and Electronic
Equipment Directive (WEEE) 2002/96/EC which sets collection, recycling and
recovery targets for electrical goods and is part of a legislative initiative to solve
the problem of huge amounts of toxic e-waste.
RoHS is often referred to as the lead-free directive, but it restricts the use of the
following six substances:
• Lead (Pb)
• Mercury (Hg)
• Cadmium (Cd)
• Hexavalent chromium (Cr6+)
• Polybrominated biphenyls (PBB)
• Polybrominated diphenyl ether (PBDE)
The maximum permitted concentrations are 0.1% or 1000 ppm (except for
cadmium, which is limited to 0.01% or 100 ppm) by weight of homogeneous
material.

27. CONTACT
vijayraskar2003@yahoo.co.in
vijay.raskar1986@gmail.com
Available at
facebook, yahoo, gmail,
linkdin, etc….

28. Thanks for reading and hope it will
helpful for you.
Trying more for best.
JUST
ENJOY