Electrical Supply

Descrição

chap2
nursyasya
Mapa Mental por nursyasya, atualizado more than 1 year ago
nursyasya
Criado por nursyasya aproximadamente 9 anos atrás
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Resumo de Recurso

Electrical Supply
  1. Principle EM induction
    1. Permanent magnet is moved relative to a conductor/vice versa, an EM force is created.
      1. Wire connected through electrical load, current flow and EMF is generated.
        1. Form of alternating sinusoidal supply.
          1. 3 coil on same spindal apart to rotate 120degree will produce 3 phase alternating supply
          2. Sinusoidal waveform
            1. Cycle
              1. Period (T)
                1. Frequency (f)
                  1. Amplitude
                  2. AC & Voltage
                    1. Effective voltage = 0.707peak voltage
                      1. Peak voltage use to express potential difference across tube:
                        1. same with photon energy emitted (keV)
                          1. voltage rating HT cables with compare to kVp applied
                          2. Vt=Vpsin2paift / lt = Ipsin2paift
                          3. 4 principle components:
                            1. generating system
                              1. by TNB in its power stations
                                1. from : coal, hydroelectric
                                  1. to rotate a turbine engine connected to alternating generator.
                                  2. transmission system
                                    1. Step up transformer
                                      1. long distance transmission
                                        1. High voltage, smaller current
                                          1. reduce of copper conductor cross section
                                        2. local distribution
                                          1. minimum power loss
                                            1. delta/star connection
                                              1. advantages
                                                1. cheaper, less liability
                                                  1. 2 diffenrent voltage
                                                2. connecting of any xray unit
                                                  1. Permantly fixed
                                                    1. mains isolator
                                                    2. Temporary connection for mobile unit
                                                      1. socket in wards.
                                                  2. Changes in main supply
                                                    1. needs stable in voltage and frequency.
                                                      1. complete stability not archieved
                                                        1. exposure draws a lot of current which produce fall in main voltage
                                                          1. slow variations over long period due to differences in demand
                                                            1. outside xray exposure
                                                            2. rapid variation in short intervals time
                                                            3. Plug & Socket
                                                              1. give maximum possible protection from electrical hazard.
                                                              2. Circuit breaker & fuse
                                                                1. protect xray circuit from damage due to overload.
                                                                2. Electrical insulation
                                                                  1. protect against effect of electric shock
                                                                    1. amount insulation for cable depend on current
                                                                      1. Cable, xray tube, transformer
                                                                      2. Earthing
                                                                        1. all electric equipment
                                                                          1. if breakdown in insulation the conductor will exposed
                                                                            1. short circuit would occur

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