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Single Phase Induction Motor Speed Control

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This project is designed to control the speed of a single-phase induction motor by using operating knob, which is commonly used in home automation applications. The main advantage of these motors is their ability to operate from a single-phase power supply – PowerPoint PPT presentation

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Title: Single Phase Induction Motor Speed Control


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Single Phase Induction Motor Speed Control
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Single Phase Induction Motor Speed Control
Introduction
  • Induction motors are widely used in many
    residential, industrial, commercial, and utility
    applications. Single-phase induction motors are
    widely used in home and industrial appliances .
    This project is designed to control the speed of
    a single-phase induction motor using an easy
    operating knob, which is commonly used in home
    automation application. The main advantage of
    these motors is their ability to operate from a
    single-phase power supply.

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Single Phase Induction Motor Speed Control
Block Diagram
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Single Phase Induction Motor Speed Control
Hardware Requirements
  • Op-amp
  • Opto-isolators
  • SCRs
  • Voltage Regulator
  • Transformer
  • Diodes
  • LED
  • Resistors
  • Capacitors
  • Lamp

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Single Phase Induction Motor Speed Control
Types of Single Phase Induction Motor
  • Split phase induction motor,
  • Capacitor start inductor motor,
  • Capacitor start capacitor run induction motor,
  • Shaded pole induction motor.

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Single Phase Induction Motor Speed Control
Power Supply
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Single Phase Induction Motor Speed Control
About Power Supply
  • The 230V AC supply is first stepped down to 12V
    AC using a step down transformer.
  • This is then converted to DC using bridge
    rectifier.
  • The AC ripples is filtered out by using a
    capacitor and given to the input pin of voltage
    regulator 7812.
  • At output pin of this regulator we get a constant
    12V DC which is used for different ICs in this
    project.

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Single Phase Induction Motor Speed Control
Induction Motor
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Single Phase Induction Motor Speed Control
Induction Motor
  • The single-phase induction machine is the most
    frequently used motor for refrigerators, washing
    machines, clocks, drills, compressors, pumps, and
    so forth.
  • The single-phase motor stator has a laminated
    iron core with two windings arranged
    perpendicularly.
  • One is the main winding
  • And
  • The other is the auxiliary winding or starting
    winding .

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Single Phase Induction Motor Speed Control
Induction Motor
  • This single-phase motors are truly two-phase
    machines.
  • The motor uses a squirrel cage rotor, which has a
    laminated iron core with slots.
  • Aluminium bars are moulded on the slots and
    short-circuited at both ends with a ring.

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Single Phase Induction Motor Speed Control
Soft Starter
  • A soft starter is another form of reduced voltage
    starter for A.C. induction motors.
  • The soft starter is similar to a primary
    resistance or primary reactance starter in that
    it is in series with the supply to the motor.
  • The current into the starter equals the current
    out.
  • The soft starter employs solid state devices to
    control the current flow and therefore the
    voltage applied to the motor.

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Single Phase Induction Motor Speed Control
Soft Starter
  • Soft starters are connected in series with the
    line voltage applied to the motor, or can be
    connected inside the delta loop of a delta
    connected motor, controlling the voltage applied
    to each winding.
  • Voltage control is achieved by means of solid
    state A.C. switches in series with one or more
    phases. These switches comprise either

c. Two SCRs
b. Diode SCR
a. Triac
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Single Phase Induction Motor Speed Control
SCR - Silicon Controlled Rectifier
  • A Silicon Controlled Rectifier (or Semiconductor
    Controlled Rectifier) is a four layer solid state
    device that controls current flow.
  • An SCR can be seen as a conventional rectifier
    controlled by a gate signal.
  • It is a 4-layered 3-terminal device.
  • When the gate to cathode voltage exceeds a
    certain threshold, the device turns 'on' and
    conducts current.

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Single Phase Induction Motor Speed Control
SCR - Silicon Controlled Rectifier
  • The operation of a SCR can be understood in terms
    of a pair of tightly coupled Bipolar Junction
    Transistors.
  • SCR has Three States
  • Reverse blocking mode, Forward blocking mode, and
    Forward conducting mode.

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Single Phase Induction Motor Speed Control
Comparator
  • Op amps comparators look very similar.
  • But a comparator gives a logic output indicating
    the relative potentials on its two inputs.
  • An op amp amplifies the differential voltage
    between its two inputs and is designed always
    to be used in closed-loop applications.
  • Potential dividers are connected to the inverting
    and non inverting inputs of the op-amp to give
    some voltage at these terminals.

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Single Phase Induction Motor Speed Control
Comparator
  • Supply voltage is given to V and V is connected
    to ground.
  • The output of this comparator will be logic high
    (i.e., supply voltage) if the non-inverting
    terminal input is greater than the inverting
    terminal input of the comparator.
  • If the inverting terminal input is greater than
    the non-inverting terminal input then the output
    of the comparator will be logic low (i.e., gnd).

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Single Phase Induction Motor Speed Control
Working Principle
  • To start the motor with low current, two
    anti-parallel SCRs connected in series with an
    induction motor to the utility supply. When the
    project is in operation, the firing angle is
    adjusted according to the requirement, which
    leads to changed intensity of a lamp or speed
    control of an induction motor. An op-amp operates
    in comparator mode that compares with zero
    voltage pulses to develop a saw-tooth voltage.
  • This saw tooth waveform is further compared
    against a varying voltage by a potentiometer for
    the level comparator to develop delayed pulses
    for triggering the SCRs. A lamp is provided in
    this project in place of an induction motor for
    demonstration purpose.

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Single Phase Induction Motor Speed Control
Advantages
  • Single phase motor is that it requires a two wire
    supply
  • Single-phase motors are less expensive to
    manufacture than other motors.
  • Capacitor-start motors are good general purpose
    motors and they are ideal for most occasions.
  • The single phase motors are simple in
    construction, cheap in cost, reliable and easy to
    repair and maintain.

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Single Phase Induction Motor Speed Control
Disadvantages
  • Single phase motor are that their power is
    limited.
  • They do not have good starting torque and they
    have a complex starting switch in some cases.
  • Speed control of induction motors are difficult.
  • At low loads, the power factor drops to very low
    values

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Single Phase Induction Motor Speed Control
Applications
  • Single phase motor finds its application in
  • Vacuum Cleaner
  • Fans
  • Washing machine
  • Centrifugal pump
  • Blowers
  • Small toys

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Single Phase Induction Motor Speed Control
Further Enhancement
  • The project can be enhanced by using six SCRs,
    two connected in back to back for each phase for
    a three phase load and the same project can also
    be enhanced to run motor in both the directions.

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Single Phase Induction Motor Speed Control
Conclusion
  • Single phase power system is widely used in
    domestic purpose, commercial purpose and to some
    extent in industrial purpose. As the single phase
    system is more economical and the power
    requirement in most of the houses, shops, offices
    are small, which can be easily met by single
    phase system. The single phase Induction motors
    are simple in construction, cheap in cost,
    reliable and easy to repair and maintain.

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