FEEDBACK
CONTROL
SYSTEM
CANTOR, RANIEL REY P.
BSEE4B
1. Show and Explain the internal parts of a contactor and its terminal designation.
❑ An electrical contactor is used in a
wide range of situations where there
is a need to switch power to a circuit
repeatedly. Like relay switches, they
are designed and built to perform this
task over many thousands of cycles.
❑ An electrical contactor is used in a
wide range of situations where there
is a need to switch power to a circuit
repeatedly. Like relay switches, they
are designed and built to perform this
task over many thousands of cycles.
Contactor Wiring Diagram
A common example of a contactor
wiring
diagram
might
look
something like this. This example
diagram would be for a three-pole
contactor with one N.O. base
contact.
1. Show and Explain the internal parts of a contactor and its terminal designation.
What Do A1 and A2 Mean on a Contactor?
A1 and A2 on a contactor typically refer to
either end of the electromagnetic coil
assembly. Most contactor manufacturers
use A1 and A2 to designate the two
terminals connecting electrical power to
the contactor’s magnetic coil.
What are 13 and 14 on a Contactor?
13 and 14 on a contactor also refer to
common manufacturer designations. In
this case, they are used to label the
terminals on the normally open contacts
in the device.
A contactor is an electrical
device that is widely used for
switching circuits on and off. As
such, electrical contactors form a
subcategory
of
electromagnetic switches known as
relays.
1. Show and Explain the internal parts of a contactor and its terminal designation.
1. Terminal bar
- The terminal bar is a connection point at the input,
output, or intermediate point of a device, or a point
at which a voltage is to be applied.
2. Moving contact
- Moving contact is the portion that moves
physically under variable operating conditions. It
moves after the energization or de-energization of
the coil.
3. Fixed contact
- Fixed contact is the stationary contact in a
contactor. After the coil energization moving
contacts touch the fixed contacts.
4. Operating coil
- The coil is a long conductor or group of conductors
wound into a tight helical package, often in several
layers on a cylindrical form.
1. Show and Explain the internal parts of a contactor and its terminal designation.
5. Armature
The armature connects the switching part to
the mechanical action of the electromagnetic
part.
6. Core
The core is the body or form on which a coil is
wound. It can be made of ferromagnetic or
dielectric material. The properties depend on
the application.
7. Coil terminals
Coil terminals are the connection points that
connect the energy to the magnetic coil. Many
contactor manufacturers use the designations
A1 and A2 for coil terminals.
8. Arc chute
An Arc chute is a set of metal plates that are
arranged in parallel and mutually insulated
from each other, which can safely extinguish
an electric arc inside the contactor.
9. Shading coil
The shading coil is a coil used in a contactor
to prevent chatter.
2. What is Modular Contactor
Modular contactors are a group of devices
- actuators, which allow for economical
and safe control of the current flow in
electrical installations. They are used,
among others, in control systems for
heating, lighting, ventilation and electric
motor
power
supply
systems.
A modular contactor is a type of
mechanical connector that is mounted on
a rail in control cabinets. The design of the
contactor consists of working contacts one or more pairs, a coil and an
electromagnet.
3. What is the difference between DC and AC magnetic contactor
•
•
DC and AC contactors operate on
different principles. DC contactors use a
magnetic field generated by the coil to
move the contacts, while AC contactors
rely on the magnetic field created by the
alternating current to move the contacts.
The structure of DC contactors and AC
contactors is quite different. DC
contactors typically have fewer poles and
require a magnetic coil to operate the
contacts, while AC contactors have more
poles and operate through the magnetic
field generated by the AC voltage.
AC
DC
Basic Contactor Construction
A contactor has three primary components:
1. The contacts are the current carrying part of
the contactor. This includes power contacts,
auxiliary contacts, and contact springs.
2. The electromagnet (or “coil”) provides the
driving force to close the contacts.
3. The enclosure is a frame housing the contact
and the electromagnet. Enclosures are made of
insulating materials like Bakelite, Nylon 6, and
thermosetting plastics to protect and insulate
the contacts and to provide some measure of
protection against personnel touching the
contacts. Open-frame contactors may have a
further enclosure to protect against dust, oil,
explosion hazards and weather.
Contactor Operation and
Symbol
Basically, a magnetic contactor works
on the same principle as a relay,
connecting and disconnecting
electricity. The actuators are similar,
this device uses a coil, which when an
electrified coil creates a magnetic field.
This magnetic field can control the
contacts that exist in magnetic
contactors.
4. Submit the terminal allocation for ac magnetic contactor
13 and 14 are the terminals of the normally
open auxiliary contacts. The terminals of the
normally closed auxiliary contact are 21 and
22.
A1 and A2 are the coil terminals of the
contactor. A1 is the positive electrode and A2 is
the negative electrode.
What caused the contactor to fail or jam?
• Overcurrent flows through the contacts.
• Apply low or high voltage to the coil.
• Dust, corrosion or vibration in the
environment.
• Wrong product selection.
• Shortcircuits are caused by the electromotive
force.
• Transients and voltage fluctuations.
• Ambient temperature.
5. What is earth leakage current
Earth leakage current is not specifically defined in BS 7671:2018+A1:2020, it is
referred to as protective conductor current. Protective conductor current is
defined as an ‘electric current appearing in a protective conductor, such as leakage
current or electric current resulting from an insulation fault.’
Leakage current is also defined as ‘electric current in an unwanted conductive path
under normal operating conditions.’
Earth leakage current can exist through an insulation fault in cables or
equipment, or it can occur under normal operating conditions in electronic
equipment which use capacitors for filtering purposes in power supplies which
can cause leakage to Earth when functioning.
5. What is earth leakage current
Leakage Current is the residual flow
of current through insulation after a
high voltage has been applied for a
period of time. Earth Leakage
Current is the leakage current from
all earthed parts of the product. The
current flowing from the mains
supply through or across insulation
into the Protective Earth Conductor.
6. What is the difference between Miniature circuit breaker ( MCB) and
Residual circuit breaker with over current ( RCBO)
MCB stands for Miniature Circuit Breaker and RCBO stands for Residual Current
Breaker with Overcurrent.
MCB is used to protect against overload and short-circuit. But, RCBO is used to
protect against earth leakage fault current with over-current also. Many do not
know the exact meaning of earth leakage fault; let us understand it first. In a
normal circuit, line and neutral currents will always be equal and balanced. But,
whenever there is an earth leakage, as the leakage current flows through the
earth, there will be an imbalance in both these currents as the line current will be
higher than the neutral current. This difference in current is called residual
current.
6. What is the difference between Miniature circuit breaker ( MCB) and
Residual circuit breaker with over current ( RCBO)
The major difference that separates both circuit breakers is that RCBO has the
additional protection of earth leakage current. Basically, it majorly uses
microcontrollers and it can also be said as a combination of MCB and RCCB. That
is why; it is more useful than MCB; because MCB does not provide protection
against the earth-leakage current.
MCB is selected based on the load, maximum short-circuit current it can
interrupt, and trip curve. RCBO too is selected on the basis of these three things;
but apart from that, it also considers maximum leakage current.
6. What is the difference between Miniature circuit breaker ( MCB) and
Residual circuit breaker with over current ( RCBO)
Cost-wise, RCBO is costlier than MCB.
MCB is used to protect lighting circuits, air conditioners, and other home
appliances; but RCBO is used mainly to interrupt power to water heaters, power
sockets, etc. where there is the possibility of electric shocks to humans.
MCB does not provide protection against electric shocks to humans, but RCBO
provides protection against electric shocks. This is because the role of RCBO is
primarily to detect earth leakage and trip the circuit when detected. Earth
leakage is dangerous for the human body. Typically, the human body can
withstand a shock of 30mA. After this, it can lead to paralysis or even death for
weaker human hearts. And, earth leakage current typically starts from 10mA and
can go beyond 30mA.
6. What is the difference between Miniature circuit breaker ( MCB) and
Residual circuit breaker with over current ( RCBO)
The breaking capacity of RCBO is
much higher than MCB (typically
up to 10kA).
Some RCBO’s also have
indicators on them to show any
earth fault trip. This feature is
very helpful as it quickly aides
the engineer in troubleshooting
faults. Such a feature is not
available in MCB’s.
W
i
r
i
n
g
C
o
n
n
e
c
t
i
o
n
f M
o o
r t
o
1 r
W
i
r
i
n
g
C
o
n
n
e
c
t
i
o
n
f M
o o
r t
o
1 r
W
i
r
i
n
g
C
o
n
n
e
c
t
i
o
n
f M
o o
r t
o
2 r
W
i
r
i
n
g
C
o
n
n
e
c
t
i
o
n
f M
o o
r t
o
2 r
THANK YOU
End of Presentation