Ramp and Pedestal Triggering

      The circuit for ramp and pedestal triggering of two SCR’s connected in antiparallel for controlling power in an AC load.  This circuit, R acts as a potential divider. Wiper (pot) R controls the value of pedestal voltage. The  diodes allows the capacitor C to be quickly charged to V through the low resistance of the upper portion of R.


The position wiper (Pot)  on R always setting the voltage v is less than the UJT firing voltage . When the wiper setting is such that is small, the voltage V charges the capacitor Vc reaches and UJT starts conduction. A pulse produced at the primary as well as at secondaries of the transformer due to discharging of capacitor through UJT and primary of the pulse transformer.
Comments (1)
  1. Michael February 22, 2016

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