Enerpro Document No: OP-0106, Rev. B
Page 4 of 14
ECO #19-11089; Release Date: 08/02/2019
The soft-stop and soft-start time constants are independently configurable via two timing resistors
(R15 and R14 respectively) and a capacitor (C2). The soft-stop and soft-start times are as follows
(where R is in kΩ, C is in uF, and t is in milliseconds):
t
soft-stop
= 1.84(R15)(C2)
t
soft-start
= 0.58(1.5 + R14)(C2)
9.0
Power-On Reset
A power-on reset circuit inhibits SCR gating until the onboard regulator establishes the 12 Vdc rail
voltage. This circuit has the added benefit of inhibiting SCR gating during severe line voltage
transients or dropouts.
10.0
Low Signal Inhibit
A low-signal inhibit circuit instantly inhibits firing when the SIG HI voltage is less than
approximately 0.48 Vdc. Operational amplifier U2D functions as a comparator whose output
instantly inhibits the firing circuit through diode D6. Omit D6 to remove the low signal inhibit
function.
11.0
Gate Pulse Profile
The firing circuit uses a phase-locked loop (PLL) circuit locked to the single phase mains voltage.
A series of counters divide the PLL’s oscillator output and a decoder section then generates two
180°-wide delayed logic signals. These logic signals are modulated by the PLL’s voltage
controlled oscillator (VCO) output signal which operates at 256 times the line frequency.
The gate logic signals are amplified by a Darlington transistor array, which excites the primary
windings of two isolated pulse transformers. The primary winding of each pulse transformer is
also connected to a current-limiting resistor and a speed-up capacitor; this provides an initial
hard-firing gate pulse followed by sustaining, lower amplitude picket fence pulses. Figures 2 and
3 show a single gate pulse burst profile and the detail of the first hard-firing pulse.
Each pulse module consists of a 2:1 ratio pulse transformer tested for 3500 V
RMS
isolation, two
secondary diodes, noise suppression resistors across both the primary and gate drive output, and
a fusible link in series with the output. Each pulse module is potted in a silicone insulating
material.
The DDFO4100 (delay determinator fiber optic) is a version of the FCOG4100 with fiber optic
outputs replacing the pulse transformers. Four FO1024 modules are installed which feature
Avago HFBR-1412Z fiber optic transmitters in lieu of the EP1024 modules. The transmitters
feature ST (bayonet) style connectors, operate at 820 nm and are directly compatible with the
MVTB series of medium voltage trigger boards. Each module has an LED to indicate that the fiber
optic transmitter is operational. Please specify this configuration on your ordering documents or
contact Enerpro for additional information.
