Overview

The firing card is the control interface between the Digital Control and Monitoring Unit (DCMU) and the Solid State Relay (SSR). It generates the control signals required to regulate output current.

Primary Function

The firing card sends timed control signals to the SSR. It determines conduction timing. It controls transformer excitation. It helps maintain the programmed current level. It is a key part of the electronic current regulation system.

Role in Current Regulation

The CCR maintains constant current by adjusting the energy delivered to the ferroresonant transformer. The firing card receives control instructions from the DCMU. It translates those instructions into switching signals. It controls when the SSR conducts during each AC cycle. This timing directly affects output current regulation.

Interaction with Other Components

The firing card works in coordination with the SSR (power switching), current transformers (feedback), and DCMU (command and monitoring system). It does not operate independently; it functions as part of the control loop.

Brightness Step Control

When a brightness step is selected, the DCMU determines the target current level. The firing card adjusts SSR conduction timing. Output current stabilizes at the programmed percentage.

Fault Conditions

If irregular current conditions occur, the firing card may stop driving the SSR. The control system may log a fault. Output may be disabled for protection.

Service Considerations

The firing card is part of the control circuitry. Before servicing, de-energize the CCR. Follow proper lockout/tagout procedures. Verify absence of voltage. Improper handling may result in damage to sensitive electronic components.

Airport Lighting Company | Type L-828, Type L-829 Ferroresonant Constant Current Regulator