electrical workshop practical

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ELECTRICAL WORKSHOP PRACTICAL

• PRESENTED
• BY
• M. SIVA BAARATHI

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INTRODUCTION

• This is very useful subject for all the students
  in electrical department who aspire to become an
  electrical technician expert and by which he can
  earn by setting up his own service center
• This session will cover the basic tools and
  safety equipments.Dismantelling,studying the
  parts and reassembling of iron box, mixer grinder
  and micro wave oven will be demonstrated
  servicing of the electrical appliances

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Electrical tools

• Screw driver
• Cutting pliers
• Wire stripper
• Hammer
• Spanner set
• Line tester
• Etc

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Personal protecting equipments

• Safety helmets
• Goggles
• Safety gloves
• Nose mask (or) dust mask
• Ear plug
• safety belt

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IRON BOX

• It is an appliance used for ironing textile
  materials, which is heated by means of an
  electric heating unit.
• Types
• Non automatic
• Automatic

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IRON BOX PARTS

• Sole plate
• Pressure plate
• Heating element
• Thermostat control unit

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Iron box parts

• SOLE PLAT
• It is made up of cast iron and generally
  chromium plated Heating element is clamped to the
  sole plate between the sheets of mica asbestos
  fitted above the heating element ,prevents heat
  radiation
• PRESSURE PLATE
• It is made up of cast iron and keeps the
  heating element in position It is bolted on the
  top of the asbestos to ensure the evenly
  distribution of heat through the sole plate

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IRON BOX PARTS

• HEATING ELEMENT
• It consist of nichrome strip. It is clamped
  in the sole plate and used for heating
• THERMOSTAT CONTROL UNIT
• It is an essential part of an automatic iron .
• It has two strips of metal ( Bimetallic
  strip).out of this one is fixed and second is
  movable according to the temperature.

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IRON BOX PARTS

• In the normal conditions both the strips of the
  thermostat are joined together perfectly.
• Strips can be tied from one side with the help of
  the screw on the increase of temperature one
  strips bends and it is contact with the other
  strips breaks

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Ranges used
Appliances Capacity Current rating of MCB
Iron box 750w 5A
Iron box 1250w 7.5A
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MIXER GRINDER

• The use of mixie in the homes now become very
  common .it is used at home level for making juice
  ,drinks and spices

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MIXER GRINDER

• PARTS OF MIXER GRINDER
• Electric motor
• Speed control switch
• Over load reset switch

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PARTS OF MIXER GRINDER

• ELECTRIC MOTOR
• The motor used in mixer grinder is generally
  universal motor
• The motor is fitted to the base unit with its
  shaft in vertical position
• Universal motor can run on both AC and DC.They
  have high starting torque and speed.

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PARTS OF MIXER GRINDER

• SPEED CONTROL SWITCH
• It is a three speed switch low ,medium and high
  the speed can be selected by rotating the knob
  of the switch
• OVER LOAD RESET SWITCH
• It is used to protect the motor from its over
  load condition
• If the motor gets over loaded, it automatically
  gets switched OFF. The motor can again be started
  after pressing the over load reset switch

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Connection diagram for mixer grinder
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Ranges used
Appliance Capacity Speed
Mixer grinder 500W to 1500W 3000 to 14000 RPM
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Ceiling fan

• Generally most of ceiling fans are capacitors
  start single phase induction motor
• Ceiling motors are differs from usual motor that
  it central portion(rotor) , remain fixed while
  the outer portion (stator) rotates.
• Capacitor is used for giving starting torque to
  the fan .
• A regulator is connected in series with the fan
  for speed control

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Parts of ceiling fan
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Connection diagram of ceiling fan
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Troubleshoot of ceiling fan

• FAN IS NOT RUNNING
• FAN IS NOISY
• FAN WOBBLES EXCESSIVELY
• MOTOR RUNS HOT

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Troubleshoot of ceiling fan

• FAN IS NOT RUNNING
• There may be no incoming supply . So check the
  concerned Branch circuit fuse and ensure the
  availability of supply in the fan circuit.
• Check for the supply in the outgoing lead from
  the regulator in the fan . If any fault is
  observed in the switch or regulator or in the
  cables rectify it .
• Ensure free rotation of the fan.
• Check the capacitor

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Troubleshoot of ceiling fan

• FAN IS NOISY
• The noise is due to the following reasons
• Loose or missing screws
• Lack of lubrication
• Worn out bearing or bush
• Slack capacitor housing
• Slack canopy-touching the rotating body

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Troubleshoot of ceiling fan

• FAN WOBBLES EXCESSIVELY
• This is due to the following reasons
• The screw which attach fan blade flanges to the
  motor hub must be in tight position
• The flanges seated incorrectly

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Troubleshoot of ceiling fan

• MOTOR RUNS HOT

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Micro wave oven
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Introduction

• The microwave oven is an important dome. Micro
  wave ovens are popular for cooking a variety of
  foods and reheating previously cooking foods.
• A microwave oven heats the food by passing
  microwave radiation through it.
• The microwave frequency is roughly 2500mega
  hertz(2.5GHz)

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Introduction

• The items to be cooked are absorbs microwaves and
  they are get heated .
• The capacity of an oven is expressed in litres
• Microwave ovens cooking is quicker and highly
  efficient.

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Parts of micro wave oven

• POWER TRANSFORMER
• HV CAPACITOR AND HV DIODE
• MAGETRON
• WAVE GUIDE
• MICROWAVE CAVITY
• TURNTABLE ASSEMBLY

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Parts of micro wave ovens

• POWER TRANSFORMER
• It is the power source of the micro wave oven.
• A supply voltage 230V AC is stepped up as 2100V
  by power transformer
• HV CAPACITOR AND HV DIODE
• The secondary winding voltage of power
  transformer (2100V) is doubled by HV capacitor
  and HV diode.
• It referred as voltage doublercircuit.A high
  voltage capacitor is connected between
  transformer and magnetron .

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Parts of micro wave ovens

• MAGETRON
• It is used to transform the energy in to micro
  wave radiation. The micro wave radiation then
  heats the water molecules in a food .the
  molecules rise in the air .
• The molecules have a lot of room to move around
  inside the cooking chamber. The molecules will
  eventually run in to each other ,when they run
  into each other ,friction created .this friction
  then cause heat. which cause the food to cook
• The 4000V DC voltage is applied to the filament
  of magnetron, then magnetron start to produce
  micro wave

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Parts of micro wave ovens

• WAVE GUIDE
• Generated microwave is passing to microwave
  cavity through wave guide .
• Waves are spreded into microwave cavity by
  stirrer fan ,which is connected to wave guide
• MICRO WAVE CAVITY
• It is a metal cooking chamber .The items to be
  cooked is placed inside the chamber. Microwave is
  injected into the chamber for cooking

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Parts of micro wave ovens

• TURNTABLE ASSEMBLY
• Turntable is fixed at the centre of the cavity
  .The turntable is rotated to ensure uniform
  cooking

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Microwave cavity
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Top view of micro wave oven
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Back view of micro wave oven
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High voltage transformer
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HV capacitor and hv diode
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Heating coil inside the cavity
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Ranges used
Appliance Capacity voltage
Microwave oven 1KW to2.5KW 230V