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OPERATING PRINCIPLES OF MACHINES (Transformer and rotating magnetic field…

- - - - Faraday's Law
        
        A varying magnetic flux associated with the loop, induced an electromotive force (emf) across it.
      - Ampere's Law
        
        Determine the direction of varying magnetic flux
        
        Right Hand Rule
    - - Core
        
        Made up of ferromagnetic material
        
        To reduce energy loss (dissipate as heat)
        
        Transformer immersed in cooling oil.
      - Coils
        
        Three phase transformer
        
        combinations of three single phase transformers but in different coil configuration
        
        High voltage winding (connect in star configuration)
        
        Low voltage winding (connect in delta configuration)
        
        Single Phase Transformer
        
        Two coils used arranged side by side
      - Bushing
        
        Supply electrical energy
      - Conservator
        
        Controls the volume of oil
    - - 3.Es = es x Ns
      - 1. ep=es
        since magnetic flux passing through primary and secondary coil is the same
      - 2. ep= Ep/Np
      - 4. Es = (Ep/Np) Ns
      - 5.Step up
        
        Ns > Np
        
        Es > Ep
      - 6.Step down
        
        Ns < Np
        
        Es < Ep
  - - - Speed of rotation of magnetic field = synchronous speed, ws
        
        ws = (4πf) / P
        unit= rad/sec
        f=frequency of AC current P=number of poles
        
        When P increases, ws will decreases
    - - Orientation of magnetic field changes with current, but its magnitude remains the same.
    - - Coils arranged 120 degrees apart
- - - - Armature coils
        
        The place where electricity induced from magnetic field
        
        Made by iron core : To enhance magnetic flux transfer
      - Rotor
        
        Induces rotating magnetic field and AC current
        
        Made by fixed steel lamina (reduce energy current losses due to eddy current)
      - Slip ring
        
        Supply DC current to rotor from DC Generator
      - Auto voltage Regulator
        
        Control current field
        
        Increase the current field if thermal magnetic field is below desired limit.
    - - Ampere's Law
        
        Supply current from slip rings produce magnetic field
        
        Strentgh of magnetic flux (depends on current produced)
      - Faraday's Law
        
        Induces current when there is varying magnetic field
        
        Current magnitude is proportional to the rate change of magnetic flux
    - - consider: magnetic field (rotating), armature coil (stationary)
        
        Magnetic field results in magnetic flux cutting the stationary armature coil
        
        emf induced
        
        currents start to flow in one direction for the first half and vice versa.
  - - - Single phase
      - Triple phase
    - - Ampere's Law #
      - Faraday's Law #
    - - Stator
        
        made of stacking thin slotted highly permeable steel laminations
        
        Produces rotating magnetic field
        
        Supply receiver
      - Rotor
        
        Insulated iron core lamina
        
        Prevent eddy current losses
        
        aid electromagnetic induction
    - - Supply given to the winding
        
        magnetic flux generate coil due to presence of current
        
        Flux from stator cut the coil in rotor
        
        Rotor coil short circuited, current start flowing
        
        Another flux will generate rotor
        
        Rotor feel a torque and rotate through the direction of magnetic flux
- - - - Faraday's Law (Moving wire)
      - Flemming's Left Hand Rules
    - - Shunt
      - Compound
      - Series
    - - Armature core
        
        Provides a path of a very low reluctance
      - Pole coils
        
        Produces magnectic flux when current passes through
      - Field magnet
        
        Spreads out flux in air gap
        
        Reduces reluctance
        
        Act as a support
        
        Made of: Pole core, Pole shoes
      - Yoke
        
        Mechanical support for the poles
        
        Protecting shield for generator
        
        Made of : Cast iron, Cast/ Rolled steel
      - Commutator
        
        Facillitate the collection of currents
        
        Convert AC current into unidirectional current
      - armature windings
        
        Lap winding
        
        Wave winding
      - Brushes
        
        Collect current from commutator
      - Bearing
    - - Lap Winding
        
        No. of parallel path = No. of poles = No. of brushes
      - Wave windings
        
        No. of parallel path = 2
      - Commutator
        
        No. of segments = No. of armature coil
  - - - Series Motor
        
        Speed drop drastically
        
        Good starting torque
        
        Connected in series
      - Shunt Motor
        
        Connected in parallel
        
        Low starting torque
        
        Constant speed
    - - Lorentz Law
        
        When currents flow through coil, emf is induced on it
      - Flemming's Left Hand Rule
    - - Armature
      - Commutator
      - Stator
        
        Provides a constant magnetic field
      - Brushes
        
        Help to maintain contact with the power source
      - Rotor
      - Highly permeable steel layers
        
        Enhance magnetic flux interaction
    - - F= qV x B
      - I = (EMFin - EMFback) / R
      - EMF back directly proportional to Speed of motor