Page 93 - CITS - Electrician - Trade Practical
P. 93

ELECTRICIAN - CITS




           Important observations:
           1  If the load power factor is unity, both watt meters W  & W  shows equal readings. Then total power of 3 Ph.
                                                                 2
                                                            1
              Load is  P= W  + W  watts
                          1
                               2
           2  If the load power factor is lies between 0.5 & unity, watt meters W & W  shows unequal readings. Now also,
                                                                        1
                                                                             2
              total power of 3 Ph. Load is  P= W  + W  watts.
                                            1    2
           3  If the load power factor is exactly 0.5, only one watt meter W  or W shows reading and other doesn’t. Now,
                                                                    1
                                                                          2
              total power of 3 Ph. Load is  P= Reading of one watt meter.
           4  If the load power factor is less than 0.5, the needle of one of the watt meter kicks back. In that case Interchange
              the terminals of CC or PC of that particular watt meter and after which reading recorded  by that wattmeter
              should be taken Negative value. In this case the total power P= W  - W  watts.
                                                                            2
                                                                        1
           5  The power factor (PF) of the circuit / load is determined by the equation,

                                                          OR




           Tabular column:
                                                                                                 Cos ϕ=
                                                              Power (P) in
             Type of       Line          Line current (I)         watts       Total power
               load     voltage (V )                                          P= W  + W
                                 L                                                 1    2
                                       (I )     (I )   (I )    W 1     W 2
                                                         B
                                                 Y
                                        R
             Resistive
             Balanced




            Resistive +
             inductive
           Unbalanced


           Circuit Diagram:































                                                           76

                                    CITS : Power - Electrician & Wireman - Exercise 38
   88   89   90   91   92   93   94   95   96   97   98