Three Phase Firing Circuit

The firing circuit board, also referred to as the trigger board, was specially designed to accomplish heavy industrial requirements (for proper operation in a high electrical and thermal stress ambient).

Part No. 60.004

Functions of the Firing Circuit

Ø Generates the 3-phase synchronization signal(s) used by gate-pulse circuitry.

Ø Filters the synchronization voltage, to obtain an increased stability of the system

Ø Senses the lack of a phase voltage or a pronounced imbalance between the phase voltages. When this happens, it blocks

the gate pulses and signals a fault.

Ø Generates and amplifies the gate pulses. It can fire SCRs in any amperage range.

Ø Generates the control signal for the phase angle delay. Contains an interface between regulator board signals and the firing

ICs, with independent high and low clamping of the firing angle domain.

Ø Has an input for external fast inhibit of the gate pulses, but also a soft start/stop input.

Ø Contains a delay circuit that inhibits any external drive signal for several seconds after powering the board, to allow for the

stabilization of the power supply voltages.

Specific Features

Ø GATE PULSE PRESENT LEDs (yellow or

amber). These LEDs indicate that gate

pulses are present to the SCR's when

operating.

Ø FAULT Indicator. The LED illuminates

when a fault condition occurs. It can be

tied to a front panel fault light and reset

pushbutton in order to clear the fault light.

Ø SYNCHRONIZATION LOSS Indicator. This LED will illuminate in the event of a loss of sync. It may also be used to indicate

when the equipment On/Off switch is in the "Off" position.

Ø This assembly is normally sold with its companion regulator board encased in a modular enclosure that is din rail mountable

as shown above.

Ø The assembly requires input control voltages provided by PCTI's Bias Power Supply.

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