The FCOG1200 firing board is designed specifically for twelve-pulse rectifiers and controllers. An optional integral auto-balance circuit enhances phase balance, ensuring excellent power quality.


  • Ideal for power quality-sensitive applications
  • Optional auto-balance circuit
  • Integral snubber circuit
  • Configured for six-phase 12-SCR controllers and converters


The FCOG1200  includes the following features:

  • Analog Delay Angle Command Signal (SIG HI): Users may choose a variety of DC control signal ranges including 0-5 V, 0-10 V, 4-20 mA, or custom ranges.
  • Power-On Reset: A special circuit prevents unintentional SCR gating upon board power-up.
  • Soft-Start and Soft-Stop: Upon soft-start, SCR firing is enabled and the delay angle command ramps from the maximum value to the setpoint value determined by the SIG HI command signal. Upon soft-stop, the delay angle ramps from the setpoint value to the maximum value after which SCR firing is inhibited.
  • Phase Loss Inhibit: A phase loss circuit instantly inhibits SCR firing if a loss of one or more phases or gross phase imbalance is sensed on the AC line. Firing will soft-start when such a fault is cleared.
  • Instant Enable and Inhibit: A contact closure (relay, switch, transistor) instantly enables or inhibits SCR firing at the delay angle commanded by the SIG HI delay angle command signal.
  • Phase Balance Circuit: The FCOG1200 provides three methods of trimming the nominal 30-degree group delay angle to optimize the rectifier performance: on-board (manual), on-board (auto), and external (auto). The 30-degree delay angle trim balances parallel bridge currents, ensuring full utilization of phase shift transformer secondary windings. Mains current harmonics and DC ripple voltage are also minimized.
  • High Current Picket Fence Gate Drive: The twelve transformer-isolated and 30-degree spaced gate drive circuits provide a hard firing initial 15 V open circuit/1.8 A short circuit firing pulse followed by sustaining "back porch" pulses at 7 V open circuit/0.5 A short circuit. The gate pulse burst frequency is 384 times the mains voltage frequency.
  • Analog Delay Determinator Circuit: Enerpro's gate delay determinator circuit is a six phase phase-locked loop consisting of a summing junction, low-pass filter, voltage controlled oscillator implemented with two proprietary ASIC devices. The VCO frequency is locked to the power line frequency. The DC delay angle command signal (SIG HI) varies the delay angle.
  • Control Power Options: The FCOG1200 is powered from an external 30 VDC or 24 Vac source.
  • Board Construction: All circuit boardsare assembled at the Enerpro plant in Goleta, California and are manufactured by a UL-approved fabricator from 2.4 mm thick FR4 fire resistant fiberglass epoxy laminate. All boards are conformal coated (MIL-1-46058, Type UR).


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