Power Factor Meter

The single-phase meter contains a fixed coil that carries the load current, and crossed coils that are connected to the load voltage. There is no spring to restrain the moving system, which takes a position to indicate the angle between the current and voltage. The scale can be marked in degrees or in power factor.

The angle between the currents in the crossed coils is a function of frequency, and consequently each power-factor meter is designed for a single frequency and will be in error at all other frequencies.

A  power  factor  meter  is  a  type  of  electrodynamometer  movement  when  it  is  made  with  two movable coils set at right angles to each other.   The method of connection of this type of power factor  meter,  in  a  3f  circuit.  

The  two  stationary  coils,  S  and  S1,  are connected in series in Phase B.   Coils M and M1 are mounted on a common shaft, which is free to move without restraint or control springs.  These coils are connected with their series resistors from  Phase  B  to  Phase  A  and  from  Phase  B  to  Phase  C.    At  a  power  factor  of  unity,  one potential  coil  current  leads  and  one  lags  the  current  in  Phase  B  by  30°;  thus,  the  coils  are balanced in the position shown in Figure. 



A change in power factor will cause the current of  one  potential  coil  to  become  more  in  phase  and  the  other  potential  coil  to  be  more  out  of phase with the current in Phase B, so that the moving element and pointer take a new position of balance to show the new power factor.




Fig(Power Factor Meter)

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