Download OVERLOAD PROTECTION CKT

PRESENTATION ON THE TOPIC
By: Rahul agarwal
INTRODUCTION
Overload protection circuit are required in
inverters
and
uninterrupted
power
supplies to make sure that the loads
connected to them don’t exceed the
maximum power rating.
PRINCIPLES
MATERIALS USED IN OPC
 OPTOCOUPLER
 IC 555
 RELAY ( N/C)
OPTOCOUPLER
The MCT & MCT 2E devices consists of a
gallium arsenide infrared emitting diode
optically couples to a monolithic silicon
phototransistor detector.
APPLICATION OF OPTOCOUPLER
• General purpose switching circuit
• Interfacing and coupling system of
different potentials & impedances
• I/O interfacing
• Solid state relays
• Monitor & detection circuit
555 TIMER IC
• The 555 timer IC is an integrated circuit
(chip) used in a variety of timer, pulse
generation and oscillator applications.
PINS OF 555 TIMER IC
PIN
1
2
NAME
GND
TRIG
PURPOSE
Ground, low level (0V)
Out rise & interval starts, when this input
fall below 1/3Vcc
3
OUT
This output is driven to +Vcc or GND
4
RESET
5
6
7
8
A timing interval may be interrupted by
driving this input to GND
CTRL
“Control” access to the internal voltage
divider (by default,2/3 Vcc)
THR
The interval ends when the voltage at
THR is greater than at CTRL
DIS
Open collector ; may discharge a
capacitor between interval
V+,Vcc Positive supply voltage is usually between
Relay
• What is a relay?
• We know that most of the high end industrial application devices
have relays for their effective working. Relays are simple switches
which are operated both electrically and mechanically. Relays
consist of a n electromagnet and also a set of contacts. The
switching mechanism is carried out with the help of the
electromagnet. There are also other operating principles for its
working. But they differ according to their applications. Most of the
devices have the application of relays.
• Why is a relay used?
• The main operation of a relay comes in places where only a lowpower signal can be used to control a circuit. It is also used in
places where only one signal can be used to control a lot of circuits.
The application of relays started during the invention of telephones.
They played an important role in switching calls in telephone
exchanges. They were also used in long distance telegraphy. They
were used to switch the signal coming from one source to another
destination. After the invention of computers they were also used to
perform Boolean and other logical operations. The high end
applications of relays require high power to be driven by electric
motors and so on. Such relays are called contactors.
• This article shows you how to test a relay. A relay will usually have
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a coil, pole terminal and a set of contacts. The set of contacts that
are open when the relay is not energized are called normally open
(N/O) contacts and the set of contacts that are closed when the
relay is not energized are called normally closed (N/C) contacts. The
following steps can be used to perform the testing of the relay using
a multimeter.
Keep the multimeter in the continuity check mode.
Check for continuity between the N/C contacts and pole.
Check for discontinuity between N/O contacts and the pole.
Now energise the relay using the rated voltage. For example use a
9V battery for energising a 9V relay. The relay will engage with
clicking sound.
Now check for continuity between N/O contacts and pole.
Also check for discontinuity between N/C contacts and pole.
As a final test, measure the resistance of the relay coil using a
multimeter and check whether it is matching to the value stated by
the manufacture
• Relay Applications
• Relays are used to realize logic functions. They play a very
important role in providing safety critical logic.
• Relays are used to provide time delay functions. They are used to
time the delay open and delay close of contacts.
• Relays are used to control high voltage circuits with the help of low
voltage signals. Similarly they are used to control high current
circuits with the help of low current signals.
• They are also used as protective relays. By this function all the
faults during transmission and reception can be detected and
isolated.