Ferroresonant L-828/L-829 CCR Description
2009 ADB Airfield Solutions, Incorporated
96A0288T 2-8
All rights reserved Issued 9/04
URC PCB Inputs/Outputs
The URC receives the inputs listed below. See Figure 2-4 in this section
and Figure 8-1 in the Wiring Schematics section.
• Local control signals from the front panel rotary switch
• Remote control signals from a remote control terminal block
located in the L-828 chassis (120 Vac) (TB1)
• A current proportional to the output current from a current
transformer (T5)
• Phase angle reference voltage derived from control windings on
T1
• 24 Vac center tapped supply voltage from T4
The URC provides the outputs listed below.
• A contact to complete the input contactor K1 coil circuit
• A contact to enable the Remote CCI voltage at TB1
• Gate drive signals to the SCR block used to regulate the output
current
Output Current Monitor Circuitry
The system output current is sensed by a current transformer (T5) whose
secondary is connected to J8-3 and J8-4. This current signal is passed
through a 15-ohm shunt resistor (R38), located on the URC board. For the
6.6 amp regulator, T5 provides a 100:1 step-down of the feedback current.
For 20 A regulators, this ratio is 300:1. Output current steps 1-5 would
correspond to voltage levels of 420, 510, 615, 780, and 990 millivolts
respectively.
Local Control Position Detection
Local control position detection is accomplished by using a rotary switch
mounted on the front door of the CCR. See Figure 2-1.
Contactor Drive
The contactor drive circuit on the URC PCB pulls in the main contactor
K2 by shorting points J4-2 to J4-4.
Remote Control Position Detection
When the local control signal to the micro-controller indicates “remote”
the remote control circuitry is active. Relay K1 on the URC board closes,
providing 120VAC to the CCI connection on TB2. The remote control
inputs incorporate surge suppression and are optically isolated from the
rest of the PCB.
Failure Protection
This subsection describes URC failure protection.
O
VERCURRENT PROTECTION
The micro-controller detects an over current condition by comparing the
output current to a preset value. If the output current exceeds this value
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