Power Controller – Syncronous Firing (Zero Cross Over)

    This is also commonly known as zero cross over firing or burst firing method. In this technique, we trigger the scr at the moment sine wave crosses zero and the anode is driven positive, the power control is achieved by having the scrs on for some cycles and off for other cycles. The ratio of no. Of cycles on to no. of cycles off is varied to proportional the power delivered to the load.

    Advantages of Syncronous Firing :

  • Conventional voltmeters and ammeters can be used for instrumentation at 50% to 100% voltage range
  • Infinitely variable output
  • Elimination of rfi
  • More uniform power distribution
  • No flickers on the lighting load
  • Achieves near unity power factor