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Transformers Transformers Transformer

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Transformers Transformers Transformer Powered By Docstoc
					Transformers
       Transformer Ratings
• VA rating
• Cooling
  – 1000 kVA 55°C ONAN
• Frequency
• Voltage
• Phase
Separate Windings

           N1

                N2

V1    I1                       V2
                     I2



      V2        N2       I1
           =         =
      V1        N1        I2
     Autotransformer

              N1



V1       I1                       V2
                   N2
                        I2


         V2        N2        I1
              =         =
         V1        N1        I2
              Connections
                             INPUT
                 Va1            Vb1   Vc1




Vc2   b2 a2




                Va3           Vb3
                       Vc3
Off Load Tap Changers
On Load Tap-Changers
   Line




   HV
 Voltage
 Varying



           Reactors
 Neutral
  End                       LV
                      8    Cont
                          Voltage
 Bypass    Vacuum     7
 Switch    Switch
                      6

                      5

                      4

                      3

           Selector   2
           Switch
                      1
B             B
          2              2

          1              1
A             A
    (1)           (2)



B             B
          2              2
                             Tap-Changer
                             Sequence of
          1              1
A             A


                             Operation
    (3)           (4)



B             B
          2              2

          1              1
A             A
    (5)           (6)


B             B
          2              2

          1              1
A             A
    (7)           (8)


B             B
          2              2

          1              1
A             A
    (9)           (10)
         Transformer Losses
• No-Load
  – Hysteresis
  – Eddy Currents
  – A tiny winding loss due to exciting current
• Winding Losses
  – Vary with the square of the load
Copper Losses
Core Losses
Laminated Core
  Transformer Hot Spot

 Thermocouple


           R


winding "hot Spot"
     oil bath




    Transformer Oil
Core Heating
      Instrument Transformers
• Step down values to safe levels for measurement
• Potential Transformers
   – Also called voltage transformers
   – Standard output 120V
• Current Transformers
   – Standard output of 1 or 5 amps
   – Metering and relaying standards
   – Can produce high voltages if open circuited
You do the Questions

				
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posted:7/2/2011
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