Page 36 - Electrician - TT (Volume 2)
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ELECTRICIAN - CITS




                                                 Half wave              Full wave                    Bridge

               Number of diodes                       1                     2                     4
               required

             Transformers peak
             output voltage





             DC output voltage
             in terms of
             V s(peak)                           0.318 Y s(peak)        0.636V V s(peak)     0.636V V s(peak)

             DC output voltage
             in terms of V                       0.45 V                 0.9 V                0.9V
                        s(rms)                         s(rms)                s(rms)              s(rms)
             Diode current
             rating                              I L(max)               0.5 I L(max)         0.5I L(max)
             Peak inverse
              voltage                            V s(peak)              2V s(peak)           V s(peak)

             Ripple frequency                    f input                2f input             2 finput



                Fig 8








           Filter circuits : Alternating current is rectified to provide a steady DC voltage similar to the output of a battery as
           shown in Fig 9a.  But the output of rectifiers in a pulsating DC as in Fig 9b.
           Pulsating DC voltages cannot be used in most of the electronic circuits.  For example a buzzing sound will be
           obtained from a radio if these pulsations are not removed in the output of the rectifiers.  The circuits used to filter off
           or reduce the pulsation in the DC output of rectifiers are known as smoothing circuits or popularly as Ripple filters.
           Ripple : The small voltage fluctuations in the output of a filter like those shown in figure 9c are called Ripple.
           Filter circuit components :  Filter circuits are normally combinations of capacitors, inductors and resistors.

           Types of filter circuits  : The different filter circuits in use are
           1  Capacitor input filter.
           2  RC filter
           3  Series inductor filter
           4  Choke input LC filter

           5  p filter.
           The rate at which the capacitor discharges between points B and C in Fig 10b  depends upon the time constant
           RLC.  longer this time constant is, the steadier is the output voltage.










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                                    CITS : Power - Electrician & Wireman - Lesson 60-69
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