switch gear and protection

1. A.D.PATEL INSTITUTE OF TECHNOLOGY
NAME:-ABHISHEK DWIWEDI(150010109007)
MIHIR RADADIYA (150010109038)
SAVAN VADHAVANA(150010109053)
SUBJECT:- SWITCH GEAR PROTECTION
TOPIC:- INDUCTION MOTOR PROTECTION

2. INTRODUCTION:
Three-phase induction motors are the most common and
frequently encountered machines in the industry.
An induction motor works on transforming action. The stator
works as the primary, while the rotor works as the secondary. It
is also called asynchronous motor.
It is simple in design, rugged, low-price and has easy
maintenance.
It runs essentially as constant speed from no-load to full load.
Its speed depends on the frequency of the power source.
It is not easy to have variable speed control and requires a
variable frequency power electronic drive for optimal speed
control.

3. An induction motor has two main parts:
Stator - It is the stationary part of the motor.
Rotor - It is the rotating part of the motor

4. Induction motor protection
 to protect an induction motor from single phasing and over temperature.
Providing a protection system is very important in industries.
 The basic idea for the development of this topic is to provide safety to the
industrial Motor etc. If any of the phases, out of the 3 phases is missing or if
the temperature of the motor during operation exceeds the threshold value,
motor stops immediately.
 The system uses a 3-Phase power supply where three single phase
transformers are connected to it. If any of the phases is not available the
corresponding transformer stops supplying power to the circuit.
 This leads to one of the four relays getting switched OFF. The main relay
which is powered through a set of four relays gets disconnected because of
one relay not being powered. Thus the main relay that delivers 3 phase supply
to the motor gets disconnected. A thermistor is connected to the motor body
to sense the temperature. If the temperature increases then supply to the
fourth relay is disconnected.

5.  The objective of dissertation is to protect the three phase induction motor
under single phasing fault. Block diagram of the protection technique is given
below in fig. 3.1 :

6. OVERVOLTAGE PROTECTION:-
 In overvoltage protection system of 3 phase induction motor, protects the
motor from overvoltage, the voltage which is higher than the rated voltage.
In circuit diagram of overvoltage protection it consists the comparator which
compare two voltages one is supply and another one is drop across the
variable resistance. When the voltage drop across the variable résistance is
higher than specified value then comparator generates signals. This signal is
fed to microcontroller and microcontroller takes the appropriate action as
shown in fig.1

7. SINGLE PHASING:-
 In single phasing protection to 3 phase induction motor, if other two phases is
faulted and only one protection of motor section starts functioning. Generally
in single phase supply voltage is lower value than specified value. On this
value of voltage motor is unable to start. Comparator which compares single
phasing supply voltage and rated specified voltage, and single sends to
microcontroller and microcontroller generates single which stop the motor if
motor is running and does not allow to motor start in case of standstill.
Sometimes single phasing protection looking much motor important when the
motor is tight which important function like furnishing, pump driving and
crane driving etc.