UNIT 202

UNIT 202

Ac Theory
1. Star Connection
2. Delta Connection
Dc Theory
1. Current
  1. The Unit is Amperes (A)
2. EMF
  1. Unit of EMF is Volts (V)
3. Resistance
  1. Measured in OHM'S
    1. The Formula Symbol R
  2. Resistors in a series circuit
    1. R1
      1. R2
        R3
    2. RT= R1 + R2 + R3
Motors
1. 3 Parts on a 3phrase
  1. Stator
  2. Electromagnets
    1. Rotor
2. single phase motors
3. 3 Phrase motors
4. 3 types of Motors
  1. Split Phase
    1. Capacitor start/capacitor - run motor
  2. Capacitor
5. DC Motors Components
  1. Field - Stays still
  2. Commutator (Attached to the armature)
    1. Armature -moving part
    2. Flips Polarity on a DC Motors, acts as a switch
  3. Carbon Brush
    1. Provide current to the moving part
      1. Conducts Elecricity
      2. Self Lubricating
    2. Soft
  4. Series
    1. Parallel
    2. Compound
6. DC Motor Components
  1. Poles
  2. Field Windings
  3. Armature
  4. Commutator
  5. Carbon Brushes
7. Synchronous Speed (ns)
  1. Speed of the magnetic field in the stator
  2. Ns ( rps ) = F/P
  3. Ns ( rpm ) = 60 X F / P
  4. Nr = Rotor speed
    1. Slip = Difference between Ns and Nr
      1. Per Unit Slip = Ns - Nr / Ns
      2. % Slip = Ns - Nr / Ns x 100
Transformers
1. Special Transformers
2. Self inductance
  1. Equation for self Inductance : L X ( L2 - L1 ) / T
    1. L = Value of Inductance in Henrys
    2. T = Time in seconds
    3. L1 and L2 = Values of Current
3. Mutual Inductance
Prefixs
1. Kilo -> k -> 1x10^3
2. mega -> M -> 1x10^6
3. GIGA -> G -> 1x10^9
4. Terra -> T -> 1x10^12
5. milli -> m -> 1x10-3
6. Micro -> yu -> 1x10-6
7. nano -> n -> 1x10-9
8. pico -> p -> 1x10-12
9. Positive
10. Negative
Floresent lighting
1. Ultra-Violet, Unless Phosphorus turns into visible light
  1. Electrodes are parts at the end of the lights
  2. Gas on the inside
2. The Ballast ( Chalk )
  1. Limits The Lamps Operating Current
  2. Provide the required voltage to start the lamp
  3. Two Types
    1. Electromagnetic
    2. Electronic

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